ALBERT

Description: 〈h3〉Abstract〈/h3〉 〈p〉Knowledge about the chemical composition of floral volatile organic compounds (VOCs) is valuable in biological studies as well as for the flavor, cosmetic, and fragrance industries. The flowers of Chinese chestnut (〈em〉Castanea mollissima〈/em〉) emit a distinctive semen-like odor; however, the chemical composition and biological role for the semen-like odor of chestnut flowers remain scarcely studied. Herein, we report the floral VOCs and the pollinators of chestnut flowers. A fast method based on a neutral desorption (ND) device coupled to extractive atmospheric pressure chemical ionization mass spectrometry (EAPCI-MS) was developed for the rapid identification of VOCs from freshly collected chestnut flowers without any chemical pretreatment. Chemical identification was performed using high-resolution MS analysis in combination with tandem MS analysis and whenever possible was confirmed by the analysis of standard reference compounds. Twenty volatiles were identified, most of which are nitrogen-containing. Out of the identified volatiles, 1-pyrroline is known to have a semen-like odor and is probably also responsible for the semen-like odor of the chestnut flowers. Four nitrogenous VOCs of chestnut flowers, including 1-pyrroline, 1-piperideine, 2-pyrrolidone, and phenethylamine, were also common in other semen-like odor flowers such as 〈em〉Photinia serrulata〈/em〉, 〈em〉Castanopsis sclerophylla〈/em〉, and 〈em〉Stemona japonica〈/em〉, suggesting similar chemical origin. The main visitors of chestnut flowers were dipteran species, such as 〈em〉Eristalis tenax〈/em〉, 〈em〉Eristalis arvorum〈/em〉, 〈em〉Episyrphus balteatus〈/em〉, 〈em〉Lucilia sericata〈/em〉, 〈em〉Chrysomya megacephala〈/em〉, 〈em〉Chrysochus asclepiadeus〈/em〉, and 〈em〉Adalia bipunctata〈/em〉. Our results suggest that the chestnut flowers and other semen-like odor flowers may present a new type of sapromyophily. This study also indicates that ND-EAPCI-MS provides more sensitive and simpler detection of many VOCs (particularly nitrogen-containing VOCs) than GC-MS and therefore can be used to complement traditional approaches for the higher chemical coverage of VOCs analysis.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉ᅟ〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2018_1487_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Ultraviolet (UV) radiation could induce pyrimidine-related dimeric lesions in genomic DNA. Though the cyclobutane pyrimidine dimers (CPDs) are the most abundant UV-induced lesions, the pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) may have more serious, potentially lethal, and mutagenic effects. It is important to have 6-4PP-containing oligodeoxynucleotides to be prepared for studying their adverse biological effects. Here, we developed a UV-irradiated water droplet method for the preparation of a biotinylated, 6-4PP-containing 10-mer oligodeoxynucleotide. By the use of HPLC purification and enrichment twice, the final yield is estimated to be about 8.1%. In contrast, without applying droplet technique, the direct UV irradiation against oligonucleotide-containing aqueous solution, the product yield is very low. The enzymatic hydrolyzation of the obtained product shows a 6-4PP characteristic ion transition of 545.12 → 432.13 in negative ion mode UHPLC-Q-TOF/MS. The established procedure for the preparation of 6-4PP-containing oligonucleotides is convenient with an improved yield.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉ᅟ〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2018_1572_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈p〉The authors would like to call the reader’s attention to the fact that unfortunately the originally provided affiliation for Dr. Tomoko Asaoka was not correct.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this project, we aimed at analyzing native (or free) amino acids with supercritical fluid chromatography coupled to mass spectrometric detection, with modern instruments and methods, and maintaining as simple a mobile phase as possible to ensure applicability of the method. The purpose was twofold: (i) a generic method allowing for satisfactory elution of a wide range of amino acids (acidic, basic, or neutral residue) and (ii) resolution of the enantiomeric pairs. The Chiralpak ZWIX (+) and (−) stationary phases were selected as they are well-known for the enantioresolution of amino acids in liquid chromatographic modes. A wide range elution gradient, starting with a large concentration of carbon dioxide (90%) and finishing at 100% solvent (methanol containing 70 mM ammonium formate and 7% water) allowed the elution of 18 native proteinogenic amino acids out of 19 injected. In these conditions, enantioselectivity was achieved for 16 of them. The basic amino acids (arginine, histidine, and lysine) were the most difficult to elute in these conditions, resulting in rather poor peak shapes. Cysteine was never observed in any of the conditions tested. Sample application was attempted with two food supplements, tablets containing a mixture of 17 proteinogenic amino acids and capsules containing taurine and theanine that were not present in the standards used for the method development. The sample preparation method was very simple, involving dissolution of the tablets and capsules in acidified water, filtration, and dilution with methanol. Mass spectrometric detection (electrospray ionization with single-quadrupole mass detection) allowed for unambiguous identification of most amino acids, except for the leucine and isoleucine isomers that were not separated by the generic gradient. The observation of taurine and theanine also suggests that the method should be generally applicable to other native amino acids than the proteinogenic amino acids selected for the development of this method. As peak shapes and signal-to-noise ratios could still be improved, further developments are wanted to upgrade this method. Due to the wide gradient (10 to 100% co-solvent in carbon dioxide), the method cannot truly be called either supercritical fluid chromatography (SFC) or enhanced-fluidity liquid chromatography (EFLC), but should be related to “unified chromatography” (UC), joining SFC and HPLC.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1783_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Chinese hamster ovary (CHO) cells are predominant in the production of therapeutic proteins to treat various diseases. Characterization and investigation of CHO cell metabolism in a quick and simple way could boost process and cell line development. Therefore, a method to simultaneously detect seven redox- and energy-related metabolites in CHO cells by capillary electrophoresis has been developed. An on-line focusing technique was applied to improve the peak shape and resolution by using a 50 μm × 44 cm uncoated fused silica capillary. Key parameters and their interactions were investigated by design of experiments (DoE) and optimized conditions were determined by desirability function as follows: 24 °C, 95 mM, and pH 9.4 of BGE. The method was validated to ensure sensitivity, linearity, and reproducibility. The limits of detection (LODs) ranged from 0.050 to 0.688 mg/L for seven metabolites, and correlation coefficients of linearity were all greater than 0.996. The relative standard deviations (RSD) of migration time and peak area were smaller than 0.872% and 5.5%, respectively, except for NADPH, and the recoveries were between 97.5 and 101.2%. The method was successfully applied to analyze the extracts from CHO cells under two different culture conditions.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1747_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Spectroscopy, a powerful tool for analyzing material structure and composition, often encounters difficulties when investigating complex systems, such as soil and water. Here, it is hypothesized that bioinformatic methods based on the definition of the operational taxonomic unit can be applied to spectral analysis and to improve the resolving power of spectroscopic approaches. To test this hypothesis, we investigated SOC structure in response to three fertilization regimes using X-ray photoelectron spectroscopy (XPS). The operational taxonomic unit in spectroscopy (OTU〈sub〉sp〈/sub〉) was defined and then the Manhattan plots were performed. Our approach turned out to be successful in determining the discrimination of SOC structure, while the traditional peak fitting method of XPS spectra failed. The results were then validated by chemical extraction analysis. Spectral analysis based on OTU〈sub〉sp〈/sub〉 can supplement traditional spectral interpretation and enhance its usability for studying complex systems.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1750_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the last decade, saliva has been suggested as non-invasive diagnostic fluid, suitable for clinical use alternatively to blood serum and plasma. However, the clinical applicability of saliva has been hampered so far by the inadequate sensitivity of current methods to detect the lower salivary concentrations of many biomarkers monitored in blood products. Herein, a label-free biosensor based on electrolyte-gated organic thin-film transistor (EGOTFT) has been developed for the detection at the physical limit of C-reactive protein (CRP) in human saliva. CRP is a key relevant biomarker for inflammatory processes and is routinely monitored for many clinical purposes. Herein, an electrolyte-gated thin-film transistor (EGOTFT) has been proposed as a transducer of the biorecognition event taking place at the gate electrode, functionalized with a self-assembled monolayer (SAM) of highly densely packed capturing anti-CRP proteins. Thanks to the SAM, the biosensing platform herein proposed is endowed with ultra-high sensitivity, along with an extremely high selectivity, assessed by measuring the dose curves of CRP interacting with a bovine serum albumin-functionalized gate. Moreover, the biosensing platform is compatible with low-cost fabrication techniques and applicable to the ultra-sensitive detection of a plethora of clinically relevant biomarkers. Therefore, the EGOTFT device herein proposed, being able to operate in physiologically relevant fluids such as saliva, will set the ground to a major revolution in biosensing applications for early clinical detection.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This review summarizes progress in analysis of glycosaminoglycans using mass spectrometry (MS) approaches. The specific areas covered include analytical challenges, disaccharide analysis, top-down and bottom-up techniques, sequence analysis, and future perspectives. A brief outline of the complexity and heterogeneity of these unique saccharides and their analysis is provided along with examples of several recent studies. Unique problems and challenges in the characterization of glycosaminoglycans are discussed along with many of the analytical tools used in particular MS methods and the types of information provided. Advances in MS-related technologies have provided more sensitive and accurate detection and sequence analysis of this complex and chemically unique class of bioconjugates. Effective MS-based methods and automated data handling with bioinformatics tools have been developed for disaccharide analysis, top-down and bottom-up analysis, and sequencing studies of relatively short oligosaccharides. It is envisioned that further improvements in MS technologies along with bioinformatics methods will make sequencing studies of longer glycosaminoglycan chains easier and faster.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Inhalation of 〈em〉Bacillus anthracis〈/em〉 spores can cause a rapidly progressing fatal infection. 〈em〉B. anthracis〈/em〉 secretes three protein toxins: lethal factor (LF), edema factor (EF), and protective antigen (PA). EF and LF may circulate as free or PA-bound forms. Both free EF (EF) and PA-bound-EF (ETx) have adenylyl cyclase activity converting ATP to cAMP. We developed an adenylyl cyclase activity-based method for detecting and quantifying total EF (EF+ETx) in plasma. The three-step method includes magnetic immunocapture with monoclonal antibodies, reaction with ATP generating cAMP, and quantification of cAMP by isotope-dilution HPLC-MS/MS. Total EF was quantified from 5PL regression of cAMP vs ETx concentration. The detection limit was 20 fg/mL (225 zeptomoles/mL for the 89 kDa protein). Relative standard deviations for controls with 0.3, 6.0, and 90 pg/mL were 11.7–16.6% with 91.2–99.5% accuracy. The method demonstrated 100% specificity in 238 human serum/plasma samples collected from unexposed healthy individuals, and 100% sensitivity in samples from 3 human and 5 rhesus macaques with inhalation anthrax. Analysis of EF in the rhesus macaques showed that it was detected earlier post-exposure than 〈em〉B. anthracis〈/em〉 by culture and PCR. Similar to LF, the kinetics of EF over the course of infection were triphasic, with an initial rise (phase-1), decline (phase-2), and final rapid rise (phase-3). EF levels were ~ 2–4 orders of magnitude lower than LF during phase-1 and phase-2 and only ~ 6-fold lower at death/euthanasia. Analysis of EF improves early diagnosis and adds to our understanding of anthrax toxemia throughout infection. The LF/EF ratio may also indicate the stage of infection and need for advanced treatments.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1730_Figo_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Comprehensive separation and analysis of non-ionic surfactants have been conducted by coupling supercritical fluid chromatography (SFC) with ion mobility spectrometry-mass spectrometry (IMS-MS). Representative non-ionic surfactants were investigated, including alkylphenol ethoxylates (APEOs), e.g., octylphenol ethoxylates (OPEOs) and fatty alcohol ethoxylates (FAEs), e.g., lauryl alcohol ethoxylates (LAEs). A sub-2-μm high-density diol column was used for chromatographic separation by the first-dimensional SFC due to the differences in ethoxy chain prior to electrospray ionization (ESI). Maintaining the fidelity of pre-ionization separation in the first dimension, the introduction of IMS provided additional post-ionization resolution by broadly fractionating the oligometric ethoxymers based on their size and electric charge within 13.78 ms. Distinguishable series of singly and multiply charged non-ionic species could be clearly observed. The millisecond timescale ion mobility separation perfectly fits the elution time of a chromatographic peak, while effectively feeding components into the fast-scanning time-of-flight (TOF) mass analyzer for characterization and analysis. The orthogonality of the developed separation and analysis system was evaluated, revealing a correlation coefficient and peak spreading angle of 0.2729 and 74.16° for the studied OPEOs and 0.1962 and 78.69° for LAEs. Significant enhancement in peak capacity was achieved for the developed SFC-IMS-MS system with the actual peak capacity measured to be approximately 41 and 160 times higher than that of the dimensions of SFC and IMS, respectively, when used alone.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1777_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉One of the current trends in green analytical chemistry is the introduction of green solvents, some of which are biobased. At the same time, the development of the biorefinery concept has allowed more biochemicals to be obtained with increased efficiency and from a wider range of feedstocks. The first examples of the use of biosolvents in analytical applications included extractions performed with alcohols, esters, and terpenes. However, many more applications of biosolvents in extractions of bioactive compounds from various plant materials have also been reported, which hints at a wider range of potential analytical applications of biosolvents. It should also be noted that the biobased solvents applied in analytical chemistry are not always green, as some of them are toxic towards aquatic organisms.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1732_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A candidate reference measurement procedure (RMP) based on isotope dilution coupled with liquid chromatography–tandem mass spectrometry (ID–LC–MS/MS) was developed and validated for the quantification of 17α-hydroxyprogesterone (17-OHP) in human plasma. 17-OHP spiked with a deuterium-labeled internal standard was extracted from plasma by liquid–liquid extraction with 1 mL 〈em〉n〈/em〉-hexane/ethyl acetate (3:2, v/v). Reversed-phase chromatography and positive electrospray ionization were used in the ID–LC–MS/MS. Gradient elution coupled with use of a C〈sub〉18〈/sub〉-packed ultrahigh-performance liquid chromatography column allowed complete baseline resolution of 17-OHP from its structural analogue desoxycorticosterone in 6 min. To determine the 17-OHP level in human plasma, a bracketing calibration method was used to give higher accuracy and precision. The limit of detection and the lower limit of the measuring interval for the candidate RMP were 2.1 pg/mL (6.4 pmol/L) and 4.6 pg/mL (13.9 pmol/L), respectively. Extraction recovery was determined to be (96.08 ± 3.03)% (〈em〉n〈/em〉 = 3). Imprecision (intra-assay and interassay) was 4.03% or less at 0.83, 15.19, 64.22, and 313.46 ng/mL (2.51, 45.97, 194.34, and 948.56 nmol/L, respectively). Recoveries ranged from 98.05% to 102.24%. When comparing our RMP results with those obtained with an established RMP via International Federation of Clinical Chemistry and Laboratory Medicine external quality assessment scheme for reference laboratories in laboratory medicine (RELA) samples, we found that the biases ranged from -1.99% to 3.08% against the targets. No interference was observed, and the linear response ranged from 0.47 to 958.63 ng/mL (1.42 to 2900.90 nmol/L). Moreover, the candidate RMP was used to measure the concentration of 17-OHP in human plasma and was compared with an immunoassay using 40 plasma samples. The performance of the method meets the needs of an RMP (total coefficient of variation of 5% or less and bias of 3.08% or less). This method can be used for reference material value assignment of 17-OHP in human plasma matrix. It could also serve as an accurate reference baseline for routine methods to increase the accuracy and precision of certain clinical laboratory measurements.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Selected ion chromatograms obtained by liquid chromatography–tandem mass spectrometry with a C〈sub〉18〈/sub〉 column for 17α-hydroxyprogesterone (17-OHP) from a plasma sample〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2086_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The establishment of fragmentation pathways has a great interest in the identification of new or unknown related compounds present in complex samples. On that way, tentative fragmentation pathways for the ions generated by atmospheric pressure ionization of neutral per- and polyfluorinated alkyl substances (PFASs) have been proposed in this work. Electrospray (ESI), atmospheric pressure chemical ionization (APCI) and photoionization (APPI) were evaluated using mobile phases and source conditions that enhance the ionization efficiency of ions generated. A hybrid mass spectrometer consisting of a linear ion trap and an Orbitrap was used to combine the information of both multiple-stage mass spectrometry (MS〈sup〉〈em〉n〈/em〉〈/sup〉) and mass accuracy measurements to characterize and establish the genealogical relationship between the product ions observed. The ionization mechanisms to generate ions such as [M–H]〈sup〉−〈/sup〉, [M]〈sup〉−•〈/sup〉, and [M+O〈sub〉2〈/sub〉]〈sup〉−•〈/sup〉 or the in-source collision-induced dissociation (CID) fragment ions in each API source are discussed in this study. In general, fluorotelomer olefins (FTOs) ionized in negative-ion APCI and APPI generated the molecular ion, while fluorotelomer alcohols (FTOHs) also provided the deprotonated molecule. Besides, fluorooctane sulfonamides (FOSAs) and sulfonamido-ethanols (FOSEs) led to the deprotonated molecule and in-source CID fragment ions, respectively. The fragmentation pathways from these precursor ions mainly involved initial α,β-eliminations of HF units and successive losses of CF〈sub〉2〈/sub〉 units coming from the perfluorinated alkyl chain. Moreover, FTOHs and FOSEs showed a high tendency to generate adduct ions under negative-ion ESI and APPI conditions. The fragmentation study of these adduct ions has demonstrated a strong interaction with the attached moiety.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2150_Figd_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Over two decades, the Organic Analysis Working Group (OAWG) of the Consultative Committee for Amount of Substance: Metrology in Chemistry and Biology (CCQM) has organized a number of comparisons for clinically relevant small molecule organic biomarkers. The aim of the OAWG community is to be part of the coordinated international movement towards accuracy and comparability of clinical measurements that will, in turn, minimize the wastage of repeat testing and unnecessary therapy to create a sustainable healthcare industry. International and regional directives/requirements on metrological traceability of calibrators and control materials are in place. Metrology institutes worldwide maintain infrastructure for the practical realization of metrological traceability and demonstrate the equivalence of their measurement capabilities through participation in key comparisons organized under the auspices of the CCQM. These institutes provide certified reference materials, as well as other dedicated value-assignment services benefiting the in-vitro diagnostic (IVD) industry, reference (calibration) laboratories and the clinical chemistry laboratories. The roles of these services in supporting national, regional, and international activities to ensure the metrological traceability of clinical chemistry measurements are described.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2153_Figt_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We report a novel, fast, and automatic SPME-based method capable of extracting a small molecule-drug conjugate (SMDC) from biological matrices. Our method relies on the extraction of the drug conjugate followed by direct elution into an electrospray mass spectrometer (ESI-MS) source for qualitative and quantitative analysis. We designed a tool for extracting the targeting head of a recently synthesized SMDC, which includes acetazolamide (AAZ) as high-affinity ligand specific to carbonic anhydrase IX. Specificity of the extraction was achieved through systematic optimization. The design of the extraction tool is based on noncovalent and reversible interaction between AAZ and CAII that is immobilized on the SPME extraction phase. Using this approach, we showed a 330% rise in extracted AAZ signal intensity compared to a control, which was performed in the absence of CAII. A linear dynamic range from 1.2 to 25 μg/ml was found. The limits of detection (LOD) of extracted AAZ from phosphate-buffered saline (PBS) and human plasma were 0.4 and 1.2 μg/ml, respectively. This with a relative standard deviation of less than 14% (〈em〉n〈/em〉 = 40) covers the therapeutic range.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2165_Figf_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Phosphonates are increasingly used as water-softening agents in detergents, care products, and industrial processes. Despite poor biodegradability, high removal rates during wastewater treatment (WWT) have been observed, owing to strong adsorption affinity to activated sludge and mineral surfaces. Due to phosphonates representing challenging analytes, no method for the compound-specific quantification of phosphonates from solid samples has hitherto been published. In order to improve the data foundation on the environmental fate of phosphonates, an analytical method based on anion exchange chromatography and detection by electrospray ionization coupled to tandem mass spectrometry (IC-ESI-MS/MS) was developed, allowing the trace quantification of phosphonates from surface water (LOQs between 0.04 and 0.16 μg/L), wastewater (LOQs between 0.6 and 2.3 μg/L), sediment and suspended matter of rivers (LOQ 〈 0.1 mg/kg), and suspended matter of wastewater (LOQ 〈 1 mg/kg). Specificity and selectivity were enhanced by the implementation of isotope-labeled internal phosphonate standards derived through synthesis. This study describes the development of a comprehensive tool set for the determination of aminotris(methylenephosphonic acid) (ATMP), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP), ethylenediaminetetra(methylenephosphonic acid) (EDTMP), 1-hydroxyethanediphosphonic acid (HEDP), and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC) during WWT and in the aqueous environment. In the investigated matrices, HEDP and PBTC were generally present in highest and EDTMP in lowest abundance. The phosphonate contents detected in river water were in the sub to low μg/L range, depending on the wastewater burden, whereas contents in the low to medium μg/L range were found in untreated wastewater. The loads of the solid phases exceeded the contents of the corresponding liquid phases by roughly three orders of magnitude. Current data imply that phosphonates undergo significant partitioning to the solid phase during WWT and in natural water bodies.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2159_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Detecting the administration of naturally occurring but synthetically derived steroids (e.g., testosterone) in routine doping controls is particularly laborious and time-consuming. Carbon isotope signatures determined by isotope ratio mass spectrometry (IRMS) have been established as the method of choice to generate confirmatory evidence in case of suspicious or atypical findings in steroid profile analyses; however, IRMS measurements require sophisticated sample preparation methods employing up to two high-performance liquid chromatography (HPLC) purification steps. Here, an alternative sample preparation approach is presented. Immunoaffinity chromatography (IAC) was employed to reduce the batch analysis time by omitting the time-consuming HPLC purification steps, while pre- and post-IAC sample handling followed published protocols. IAC exploits specific antibody-immunogen interactions, and the option of combining three immunoaffinity gels containing specific antibodies for testosterone, pregnanediol, and 11-ketoetiocholanolone into a multi-immunoaffinity sample preparation approach was assessed. Due to cross reactivities, also etiocholanolone, androsterone, 5β-androstanediol, and 5α-androstanediol were co-extracted and included in the testing protocol. The method was validated by determining precision, recovery, and carry over, and performing linear mixing models. IAC was found to be applicable to the determination of carbon isotope ratios in doping controls and the approach allowed for an accelerated sample preparation.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2169_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A label-free, rapid response colorimetric aptasensor for sensitive detection of chloramphenicol (CAP) was proposed, which was based on the strategy of ssDNA-modified gold nanoparticle (AuNP) aggregation assisted by lanthanum (La〈sup〉3+〈/sup〉) ions. The AuNPs generated a color change that could be monitored in the red, green, and blue and analyzed by the smartphone imaging app. La〈sup〉3+〈/sup〉, as a trigger agent, strongly combined with the phosphate groups of the surface of ssDNA-AuNPs probe, which helps create AuNP aggregation and the color change of AuNPs from red to blue. On the contrary, when mixing with CAP, the aptamer (Apt) bound to CAP to form a rigid structure of the Apt-CAP complex, and La〈sup〉3+〈/sup〉 attached to the phosphate groups of the complex, which prevented the aptamer from binding to the surface of the AuNPs. As a result, the color of the AuNPs changed to violet-red. Finally, UV-vis absorption spectroscopy and the smartphone imaging app were employed to determine CAP with a lower detection limit of 7.65 nM and 5.88 nM, respectively. The proposed strategy featuring high selectivity and strong anti-interference ability for detection of CAP in practical samples was achieved. It is worth mentioning that the simple and portable colorimetric aptasensor will be used for facilitating on-site detection of food samples.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, a straightforward analytical approach based on headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed for the analysis of salivary volatile organic compounds without any prior derivatization step. With a sample volume of 500 μL, optimal conditions were achieved by allowing the sample to equilibrate for 10 min at 50 °C and then extracting the samples for 10 min at the same temperature, using a carboxen/polydimethylsiloxane fibre. The method allowed the simultaneous identification and quantification of 20 compounds in sample headspace, including short-chain fatty acids and their derivatives which are commonly analysed after analyte derivatization. The proof of applicability of the methodology was performed with a case study regarding the analysis of the dynamics of volatile metabolites in saliva of a single subject undergoing 5-day treatment with rifaximin antibiotic. Non-stimulated saliva samples were collected over 3 weeks from a nominally healthy volunteer before, during, and after antibiotic treatment. The variations of some metabolites, known to be produced by the microbiota and by bacteria that are susceptible to antibiotics, suggest that the study of the dynamics of salivary metabolites can be an excellent indirect method for analysing the gut microbiota. This approach is novel from an analytical standpoint, and it encourages further studies combining saliva metabolite profiles and gut microbiota dynamics.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2158_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Food processing can lead to a reduction of contaminants, such as mycotoxins. However, for food processing operations where thermal energy is employed, it is often not clear whether a reduction of mycotoxins also results in a mitigation of the toxicological impact. This is often due to the reason that the formed degradation products are not characterized and data on their toxicity is scarce. From the perspective of an analytical chemist, the elucidation of the fate of a contaminant in a complex food matrix is extremely challenging. An overview of the analytical approaches is given here, and the application and limitations are exemplified based on cases that can be found in recent literature. As most studies rely on targeted analysis, it is not clear whether the predetermined set of compounds differs from the degradation products that are actually formed during food processing. Although untargeted analysis allows for the elucidation of the complete spectrum of degradation products, only one such study is available so far. Further pitfalls include insufficient precision, natural contamination with masked forms of mycotoxins and interferences that are caused by the food matrix. One topic that is of paramount importance for both targeted and untargeted approaches is the availability of reference standards to identity and quantity the formed degradation products. Our vision is that more studies need to be published that characterize the formed degradation products, collect data on their toxicity and thereby complete the knowledge about the mycotoxin mitigating effect during food processing.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Testosterone in human serum is commonly tested in clinical laboratories using immunoassay methods as well as liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. To standardize and ensure the accuracy of the measurement results, reference procedures with higher metrological order are required. A simple measurement procedure based on one-step liquid-liquid extraction (LLE) and liquid chromatography-isotope dilution tandem mass spectrometry (LC-IDMS/MS) was developed for total testosterone in human serum. The procedure involved serum spiked with 〈sup〉13〈/sup〉C〈sub〉3〈/sub〉-testosterone, equilibration for 2 h, and extraction with an organic solvent. Testosterone certified reference material (CRM) was used as the calibration standard to ensure the traceability to the International System of Units (SI). Testosterone in serum CRMs from the National Institute for Standards and Technology (NIST) and LGC were used to validate the accuracy of the newly developed method. The deviations of the obtained values from the NIST and LGC certified values ranged from −0.55% to 0.45%. Similarly, the coefficient of variations (CVs) of the replicate measurements were in the range of 0.55% and 0.78%, respectively. The relative expanded uncertainties were comparable with those of the certified materials. The newly developed LC-IDMS/MS procedure demonstrated adequate trueness and precision, and was simple to perform. The method can be used for value assignment of testosterone in external quality assessment (EQA) materials as well as certification of CRMs in the future.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2152_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈p〉The article Chemometric tools for the authentication of cod liver oil based on nuclear magnetic resonance and infrared spectroscopy data, written by Editha Giese, Sascha Rohn and Jan Fritsche.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Starting from simple graphite flakes, an electrochemical sensor for sunset yellow monitoring is developed by using a very simple and effective strategy. The direct electrochemical reduction of a suspension of exfoliated graphene oxide (GO) onto a glassy carbon electrode (GCE) surface leads to the electrodeposition of electrochemically reduced oxide at the surface, obtaining GCE/ERGO-modified electrodes. They are characterized by cyclic voltammetry (CV) measurements and field emission scanning electron spectroscopy (FE-SEM). The GCE/ERGO electrode has a high electrochemically active surface allowing efficient adsorption of SY. Using differential pulse voltammetry (DPV) technique with only 2 min accumulation, the GCE/ERGO sensor exhibits good performance to SY detection with a good linear calibration for concentration range varying 50–1000 nM (〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.996) and limit of detection (LOD) estimated to 19.2 nM (equivalent to 8.9 μg L〈sup〉−1〈/sup〉). The developed sensor possesses a very high sensitivity of 9 μA/μM while fabricated with only one component. This electrochemical sensor also displays a good reliability with RSD value of 2.13% (〈em〉n〈/em〉 = 7) and excellent reusability (signal response change 〈 3.5% after 6 measuring/cleaning cycles). The GCE/ERGO demonstrates a successful practical application for determination of sunset yellow in commercial soft drinks.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2155_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Intestinal diamine oxidase (DAO) acts as a protective barrier against exogenous histamine. A deficit of DAO activity can lead to the appearance of histamine intolerance, a clinical condition that may be treated by a low-histamine diet and oral DAO supplementation to enhance intestinal histamine degradation. As sources of DAO, porcine kidneys and certain legume seedlings are suitable components for the formulation of a DAO supplement. The aim of this work was to develop a rapid and reliable methodology for the in vitro determination of DAO activity in food matrices based on an enzymatic assay coupled to UHPLC-FL. The proposed method showed a satisfactory linearity and sensitivity and provided a relative standard deviation lower than 3%, guaranteeing method precision, and a mean recovery greater than 99% both for lyophilized pea sprouts and porcine kidney protein extracts. A high specificity is a key attribute of this method due to the use of histamine as the reaction substrate and the direct quantification of its degradation. Moreover, the lack of interference of catalase and hydrogen peroxide is another advantage in comparison with previously published methods. Lyophilized pea sprouts showed the greatest histamine-degrading activity (0.40 ± 0.01 mU/mg), followed by porcine kidney protein extracts (0.23 ± 0.01 mU/mg) and commercial DAO supplements (0.09 ± 0.06 mU/mg). This technique could be used as a tool to validate the DAO activity of food matrices of potential interest for the treatment of histamine intolerance.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A novel method combining headspace single-drop microextraction with a paper-based colorimetric assay was developed. Headspace single-drop microextraction using a microdrop containing unmodified gold nanoparticles (AuNPs) as both the extractant and the colorimetric probe was used for the sensitive and selective determination of Se(IV). The method relies on the color change of the microdrop solution caused by the adsorption of in situ-generated hydrogen selenide on the surface of AuNPs. Following extraction, the microdrop was spotted onto cellulose paper, and scanometric-assisted digital image analysis was used for selenium quantification. The analytical variables affecting the method sensitivity, including the drop volume, the concentrations of KBH〈sub〉4〈/sub〉, HCl, and AuNP solutions, and the extraction time, were studied. Under the optimal conditions, a linear correlation between the colorimetric signal and Se(IV) concentration in the range from 15–100 μg L〈sup〉−1〈/sup〉 with a limit of quantification of 12 μg L〈sup〉−1〈/sup〉 was achieved. The repeatability of the method was studied by the calculation of intraday and interday precision for the standard solutions at concentrations of 20 and 70 μg L〈sup〉-1〈/sup〉. The batch-to-batch reproducibility of the AuNPs synthesized under the same conditions was also assessed. The relative standard deviations were less than 7%. The method provided satisfactory results for the determination of selenium in real samples.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Biofilms are communities of bacteria living embedded in a highly hydrated matrix composed of polysaccharides, proteins, and extracellular DNA. This life style confers numerous advantages to bacteria including protection against external threats. However, they also contribute to increase bacterial resistance against antimicrobials, an issue particularly relevant in dangerous infections. Due to the complexity of the matrix, few information is present in the literature on details of its architecture including the spatial distribution of the macromolecular components which might give hints on the way the biofilm scaffold is built up by bacteria. In this study, we investigated the possibility to combine well-established microbiological procedures with advanced microscopies to get information on composition and distribution of the macromolecular components of biofilm matrices. To this, confocal microscopy, diffraction-limited infrared (IR) spectral imaging, and atomic force microscopy (AFM) were used to explore biofilm produced by a clinical strain of 〈em〉Klebsiella pneumoniae〈/em〉. IR imaging permitted to have clues on how the biofilm grows and spreads on surfaces, and the local distribution of the components within it. Through the analysis of the pure component spectra, it was possible to assess the chemical and structural composition of the saccaridic matrix, confirming the data obtained by NMR. It was also possible to follow the time course of biofilm from 6 up to 48 h when the biofilm grew into a 3-dimensional multi-layered structure, characteristic of colonies of bacteria linked together by a complex matrix. In addition, nanoFTIR and AFM investigations allowed the estimation of biofilm growth in the vertical direction and the morphological analysis of bacterial colonies at different time points and the evaluation of the chemical composition at the nanoscale.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, a sensitive amplification strategy for Pb〈sup〉2+〈/sup〉 detection using reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) was proposed. Thiol-modified DNAzyme is specific for Pb〈sup〉2+〈/sup〉 self-assembly on RGO-AuNPs-modified electrode surface. Ferrocene labeled single-stranded DNAzyme (Fc-ssDNAzyme) self-hybridizes to form a DNA hairpin structure. The amount of Fc adsorbed on the electrode surface changes after the appearance of Pb〈sup〉2+〈/sup〉, leading to a change of electrical signal. This change can be sensitively identified by differential pulse voltammetry (DPV) assisted by ferricyanide ([Fe(CN)〈sub〉6〈/sub〉]〈sup〉3−/4−〈/sup〉) in the electrolyte. The high conductivity and specific surface area of RGO and the strong chemical bond adsorption effect between DNAzyme and AuNPs are responsible for the amplified detection of Pb〈sup〉2+〈/sup〉, which realize a detection range of 0.05–400,000.0 nM and a minimum detection limit of 0.015 nM. Moreover, the selectivity test results indicated that the biosensor had specificity for Pb〈sup〉2+〈/sup〉, even if there was interference from other high-concentration metal ions. This simple biosensor also exhibited good responsiveness in actual sample detection, which provides a good application prospect for field detection of Pb〈sup〉2+〈/sup〉 in water.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2146_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Desorption atmospheric pressure photoionization (DAPPI) is an ambient mass spectrometry (MS) technique that allows the analysis of both polar and nonpolar compounds directly from the surfaces of various sample types. Here, DAPPI was used to study the chemical profiles in different parts of birch and alder tree barks. Four distinct fractions of 〈em〉Betula pendula〈/em〉 (silver birch) bark were collected from three different developmental stages of the stem, after which the chemical profiles of the different tissue types were measured. Of special interest were triterpenoids, a class of important defensive substances, which are found in the bark of the silver birch. Additionally, the chemical profiles of lenticels and the surrounding surfaces in the phellem of 〈em〉B〈/em〉. 〈em〉pendula〈/em〉 (silver birch), 〈em〉Alnus glutinosa〈/em〉 (black alder), and 〈em〉Alnus incana〈/em〉 (gray alder) were screened with DAPPI. Another ambient MS technique, laser ablation atmospheric pressure photoionization (LAAPPI), was further used for the mass spectrometry imaging of lenticels on the 〈em〉B〈/em〉. 〈em〉pendula〈/em〉 phellem. All the studied birch bark fractions showed individual chemical profiles in DAPPI. The mass spectra from the young apical stem and the transition zone resembled each other more than the mature stem. Instead, the phellem was found to contain a high amount of triterpenoids in all the developmental stages of the stem. The most intense peaks in the DAPPI mass spectra of the birch bark fractions were those of betulin and lupeol. Betulinic and betulonic acid peaks were intense as well, and these compounds were detected especially in the lenticels of the tree samples.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2171_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, chemosensors based on mixed ligands were proposed for the cooperative detection of Co〈sup〉2+〈/sup〉. The relationship between the specifically selected mixed organic ligands and the detection activities is discussed. Diverse responses to metal ions can be tuned by controlling the structural features of organic ligands, such as different sizes, geometries, substituents, and connectivity. Among the nine investigated systems, DHAB–Tpy, DHAB–Phen, and DHAB–Dpa displayed high selectivity and sensitivity for Co〈sup〉2+〈/sup〉, with detection limits of 4.5 × 10〈sup〉−7〈/sup〉 M, 1.1 × 10〈sup〉−7〈/sup〉 M, and 8.0 × 10〈sup〉−8〈/sup〉 M, respectively. The detection of Co〈sup〉2+〈/sup〉 was not affected by other metal ions, anions, amino acids, proteins, nucleic acids, lipids and pH conditions. Furthermore, the proposed method was validated in the analysis of Co〈sup〉2+〈/sup〉 in real water samples with satisfactory recovery and relative standard deviation values. TAC–Phen and TAC–Dpa could recognize Co〈sup〉2+〈/sup〉 qualitatively, but could not detect Co〈sup〉2+〈/sup〉 quantitatively. While TAC–Tpy, PAN–Tpy, PAN–Phen, and PAN–Dpa showed no metal ion selectivity. The experimental results were also rationalized by theoretical studies. A mixed ligand system can be used to produce a ratiometric absorption signal to avoid most ambiguities, such as the chemosensor environment and concentration, via self-calibration of two absorption bands. Structural insights derived from detection activities can provide valuable information for the design of new metal ion chemosensors by varying the type of organic ligands.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstracts〈/strong〉 〈em〉 〈div〉The work represents a simple strategy for obtaining synthesis-free, inexpensive, and sensitivity-tunable chemosensors through mixing organic ligands of different sizes, substitutions, geometries, and connectivity to modulate the sensing behaviors.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1707_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉G-series nerve agents, such as sarin, tabun, and soman, would cause tremendous harm in military and terrorist attacks, so it is necessary to develop a simple method for the rapid and efficient detection of these hazardous substances. We have developed a tunable acetylcholinesterase (AChE)-functionalized two-dimensional photonic crystal (2D PhC) for the detection of a real nerve agent, sarin. In accordance with the 2D PhC previously prepared by our group, the AChE-functionalized 2D PhC was optimized by adjustment of the amount of monomer in the hydrogel, which not only increased the sensitivity of the 2D PhC, with the detection limit decreasing by two orders of magnitude, but also ensured the structural color spanned the whole visible region in the detection range. A linear relationship between the logarithm of the sarin concentration and the particle spacing of the AChE-functionalized 2D PhC was observed from 7.1 × 10〈sup〉-17〈/sup〉 to 7.1 × 10〈sup〉-4〈/sup〉 mol/L. The AChE-functionalized 2D PhC also responded to mimics of G-series nerve agents, including dimethyl methylphosphonate, diisopropyl methylphosphonate, and isodipropyl methylphosphonate, to various degrees. The proposed 2D-PhC hydrogel has potential for low-cost, trace-level, and on-site monitoring of other G-series nerve agents.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1700_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The development of a novel method for melamine detection that uses a FAM–aptamer–G-quadruplex construct due to the efficient quenching ability of an aptamer-linked G-quadruplex is reported herein. The construct, which is labeled with the fluorescent dye 6-carboxyfluorescein (FAM), consists of two parts: a melamine-binding aptamer and a G-rich sequence that can form a G-quadruplex structure. Because of the specific recognition of melamine by the T-rich aptamer, this aptamer folds into a hairpin structure in the presence of melamine, which draws the G-quadruplex closer to the FAM fluorophore, leading to the quenching of the fluorescence of FAM. Thus, a highly sensitive and selective fluorescence strategy for assaying melamine was established. Under optimal conditions, the fluorescence quenching is proportional to the concentration of melamine within the range 10–90 nM, and the method has a detection limit of 6.32 nM. Further application of the method to plastic cup samples suggested that it permitted recoveries of between 97.15% ± 1.02 and 101.92% ± 2.07. The detected amounts of melamine spiked into the plastic cup samples and the corresponding amounts measured by HPLC were in good accordance, indicating that this fluorescent method is reliable and practical. Owing to its high sensitivity, excellent selectivity, and convenient procedure, this strategy represents a promising alternative method of melamine screening.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1688_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A multi-residue method was developed for the simultaneous determination of 24 plant growth regulators (PGRs) and 11 representative pesticides that were widely applied in plants used in traditional Chinese medicines (TCMs) by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS). The method was validated taking into consideration EU guidelines; calibration curves for all of the targeted analytes showed correlation coefficients (〈em〉γ〈/em〉〈sup〉2〈/sup〉) higher than 0.9901. The limits of detection (LOD) ranged from 0.2 to 8 μg/kg. The average recovery for all analytes in spiked samples ranged from 63.18 to 127.23%, with a relative standard deviation of ≤ 15%. The proposed method has been applied to 480 batches of TCM samples, including 34 species of medicinal plants, from the TCM market. The results showed that 14 PGRs and 5 pesticides were detected, including choline chloride, chlormequat, paclobutrazol, uniconazole, phoxim, etc. Among them, there were high detection rates for chlormequat (40%), choline chloride (100%), atonik (73.75%), abscisic acid (80.83%), and indole-3-acetic acid (41.25%). The residual level of paclobutrazol in Ophiopogonis radix exceeded the recommended maximum residue limits (MRLs) according to GB 2763–2016. In addition, 14 agrochemicals used in TCM planting were collected and detected; the result showed various PGRs were detected in samples registered as fertilizer. These results indicate that PGRs and pesticides were widely used in the cultivation of medicinal plants, especially for radix and rhizome herbs. The residue of targeted PGRs and pesticides in TCM samples from this study have a high frequency and high level.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1691_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Antibody–drug conjugates (ADCs) are an inherently heterogeneous class of biotherapeutics, the development of which requires extensive characterization throughout. During the earliest phases of preclinical development, when synthetic routes towards the desired conjugate are being assessed, the main interest lies in the determination of the average drug-to-antibody ratio (DAR) of a given batch as well as information about different conjugation species. There has been a trend in mass spectrometry (MS)–based characterization of ADCs towards the use of high-resolving mass spectrometry for many of these analyses. Considering the high cost for such an instrument, the evaluation of cheaper and more accessible alternatives is highly motivated. We have therefore tested the applicability of a quadrupole mass analyzer for the aforementioned characterizations. Eight ADCs consisting of trastuzumab and varying stoichiometries of Mc-Val-Cit-PABC-monomethyl auristatin E conjugated to native cysteines were synthesized and served as test analytes. The average DAR value and molecular weights (Mw) of all detected chains from the quadrupole mass analyzer showed surprisingly high agreement with results obtained from a time-of-flight (TOF) mass analyzer and hydrophobic interaction chromatography (HIC)–derived values for all investigated ADC batches. Acquired Mw were within 80 ppm of TOF-derived values, and DAR was on average within 0.32 DAR units of HIC-derived values. Quadrupole mass spectrometers therefore represent a viable alternative for the characterization of ADC in early-stage development.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1699_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The introduction of fluorine into organic molecules leads to new chemical/physical properties. Especially in the field of pharmaceutical as well as technical applications, fluorinated organic substances gain in importance. The OECD identified and categorized 4730 per- and polyfluoroalkyl substances-related CAS numbers. Thus, an increasing release of fluorinated compounds into the environment is expected. In particular, perfluorinated compounds often show higher environmental stability leading to the risk of bioaccumulation. Polyfluorinated compounds undergo decomposition; thus, further possible fluorine species occur, which may exhibit different toxic/chemical properties. However, current target methods based on, e.g., HPLC/MS-MS, are not applicable for a comprehensive screening of fluorinated substances as well as assessment of pollution. Thus, within this work, a sum parameter method for quantitative determination of extractable organically bound fluorine (EOF) in surface waters was developed. The method is based on solid-phase extraction (SPE) for extraction of fluorinated compounds as well as separation of interfering inorganic fluoride in combination with high-resolution–continuum source graphite furnace molecular absorption spectrometry (HR-CS GF MAS) for organic fluorine quantification. Upon optimization of the SPE procedure (maximum concentration of extractable organic fluorine), enrichment factors of about 1000 were achieved, allowing for highly sensitive fluorine detection. HR-CS GF MAS allows for selective fluorine detection upon in situ formation of a diatomic molecule (“GaF”). Next to a species-unspecific response, limits of detection in the low nanogram per liter range (upon enrichment) were achieved. Upon successful method development, surface water samples (rivers Moselle and Rhine) were analyzed. Furthermore, a sampling campaign along the river Rhine (from the south—close to the French border; to the north—close to The Netherlands border) was conducted. EOF values in the range of about 50–300 ng/L were detected. The developed method allows for a fast and sensitive as well as selective/screening detection of organically bound fluorine (EOF) in surface water samples, helping to elucidate pollution hotspots as well as discharge routes.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉A solid phase extraction (SPE) HR-CS GF MAS screening method was developed for the quantitative analysis/screening of extractable organically bound fluorine (EOF) in river water samples. Highly sensitive EOF analysis (low ppq range) was obtained upon SPE and HR-CS GF MAS analysis. Sampling campaign along the river Rhine was conducted.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1698_Fige_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this preliminary study, we employed surface-enhanced Raman scattering (SERS) of saliva and serum samples for diagnosing Sjogren’s syndrome (SjS), a systemic autoimmune disease characterized by dryness of the mouth and eyes. The saliva and serum samples from 〈em〉n〈/em〉 = 29 patients with SjS and 〈em〉n〈/em〉 = 21 controls were deproteinized with methanol and then the SERS spectra were acquired using silver nanoparticles synthesized by reduction with hydroxylamine hydrochloride. In the case of both saliva and serum, the SERS spectra were dominated by similar bands attributed to purine metabolites such as uric acid, xanthine, and hypoxanthine. Principal component analysis-linear discriminant analysis (PCA-LDA) models built from SERS spectra of saliva and serum yielded an overall classification accuracy of 94% and 98%, respectively. These results suggest that the SERS analysis of saliva and serum is able to capture the complex biochemical perturbations that accompany the onset of SjS, a strategy which could be translated in the future into a novel point-of-care diagnosis method.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1969_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Positive identification of capillary electrophoresis-sodium dodecyl sulfate (CE-SDS) electropherogram peaks provides information to understand protein molecular characteristics at the structural level. It is critical in the design of a robust assay that can accurately resolve, differentiate, and quantify all therapeutic protein components including fragmented species, which are considered as product related impurities. However, direct identification of the impurity peaks observed in CE-SDS is a challenging and oftentimes an ambiguous task. This paper proposed a systematic workflow for characterizing CE-SDS fragmentation peaks. Forced degradation of monoclonal antibody (mAb) by multiple stress methods was utilized to induce fragmentation and species enrichment. The characteristics, such as size and the clipped region of sequence, were then evaluated based on multiple enzymatic treatment and particle reduction. The identified fragments were further confirmed using tryptic digestion and liquid chromatography coupled with mass spectrometry (LC-MS) analysis. Common fragment sizes and clipping locations are identified after evaluating multiple IgG molecules. The methodology and procedure described in this article are readily deployable and will provide necessary information for method, process, and product characterizations.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1942_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) is increasingly popular for the non-targeted exploration of complex samples, where tandem mass spectrometry (MS/MS) is used to characterize the structure of unknown compounds. However, mass spectra do not always contain sufficient information to unequivocally identify the correct structure. This study investigated how much additional information can be gained using hydrogen deuterium exchange (HDX) experiments. The exchange of “easily exchangeable” hydrogen atoms (connected to heteroatoms), with predominantly [M+D]〈sup〉+〈/sup〉 ions in positive mode and [M-D]〈sup〉−〈/sup〉 in negative mode was observed. To enable high-throughput processing, new scoring terms were incorporated into the in silico fragmenter MetFrag. These were initially developed on small datasets and then tested on 762 compounds of environmental interest. Pairs of spectra (normal and deuterated) were found for 593 of these substances (506 positive mode, 155 negative mode spectra). The new scoring terms resulted in 29 additional correct identifications (78 vs 49) for positive mode and an increase in top 10 rankings from 80 to 106 in negative mode. Compounds with dual functionality (polar head group, long apolar tail) exhibited dramatic retention time (RT) shifts of up to several minutes, compared with an average 0.04 min RT shift. For a smaller dataset of 80 metabolites, top 10 rankings improved from 13 to 24 (positive mode, 57 spectra) and from 14 to 31 (negative mode, 63 spectra) when including HDX information. The results of standard measurements were confirmed using targets and tentatively identified surfactant species in an environmental sample collected from the river Danube near Novi Sad (Serbia). The changes to MetFrag have been integrated into the command line version available at 〈a href="http://c-ruttkies.github.io/MetFrag/"〉http://c-ruttkies.github.io/MetFrag〈/a〉 and all resulting spectra and compounds are available in online resources and in the 〈span〉Electronic Supplementary Material〈/span〉 (ESM).〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1885_Figh_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Prostate-specific antigen (PSA) is the only biomarker for the diagnosis of prostate cancer. So the PSA screening test is very important due to the high occurrence of prostate cancer in men. In this work, a label-free fluorescent method was developed based on terminal deoxynucleotidyl transferase (TdT) and G–quadruplex–thioflavin T complex for detecting PSA. In the absence of PSA, the PSA aptamer can be used as the primer for TdT extension reactions, resulting in the formation of G-quadruplexes and generation of strong fluorescent signals. After the addition of PSA, the PSA–aptamer complex prevented the TdT extension reaction due to steric hindrance, thus resulting in a poor fluorescent signal. The assay showed a wide linear range (0.1 to 80 pg/mL) and a detection limit of 0.086 pg/mL (S/N = 3). It also has good specificity for PSA determination and gives satisfactory results when applied to biological samples. Conceivably, its merits such as good selectivity and high sensitivity indicate that the proposed method has a promising application potential in the clinical diagnosis and treatment of prostate cancer.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1958_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Microfluidic paper-based devices (μPADs) and wearable devices have been highly studied to be used as diagnostic tools due to their advantages such as simplicity and ability to provide instrument-free fast results. Diseases such as periodontitis and diabetes mellitus can potentially be detected through these devices by the detection of important biomarkers. This study describes the development of μPADs through craft cutter printing for glucose and nitrite salivary diagnostics. In addition, the use of μPADs integrated into a mouthguard as a wearable sensor for glucose monitoring is also presented. μPADs were designed to contain two detection zones for glucose and nitrite assays and a sampling zone interconnected by microfluidic channels. Initially, the analytical performance of the proposed μPADs was investigated and it provided linear behavior (〈em〉r〈/em〉〈sup〉2〈/sup〉 ≥ 0.994) in the concentration ranges between 0 to 2.0 mmol L〈sup〉−1〈/sup〉 and 0 to 400 μmol L〈sup〉−1〈/sup〉 for glucose and nitrite, respectively. Under the optimized conditions, the limits of detection achieved for glucose and nitrite were 27 μmol L〈sup〉−1〈/sup〉 and 7 μmol L〈sup〉−1〈/sup〉, respectively. Human saliva samples were collected from healthy individuals and patients previously diagnosed with periodontitis or diabetes and then analyzed on the proposed μPADs. The results found using μPADs revealed higher glucose concentration values in saliva collected from patients diagnosed with diabetes mellitus and greater nitrite concentrations in saliva collected from patients diagnosed with periodontitis, as expected. The results obtained on μPADs did not differ statistically from those measured by spectrophotometry. With the aim of developing paper-based wearable sensors, μPADs were integrated, for the first time, into a silicone mouthguard using a 3D-printed holder. The proof of concept was successfully demonstrated through the monitoring of the glucose concentration in saliva after the ingestion of chocolate. According to the results reported herein, paper-based microfluidic devices offer great potential for salivary diagnostics, making their integration into a silicone mouthguard possible, generating simple, low-cost, instrument-free, and powerful wearable sensors.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Metastases are the leading causes of death in cancer patients. Due to intimate connection with metastasis, Smoothened (Smo) has become a therapeutic target for antimetastatic drugs and can provide early warning of metastasis in breast cancer. Thus, we have developed an electrochemical method in Smo analysis based on small-molecule drugs. Smo on the metastatic cell surface can be internalized after combination with the small-molecule drug. The surplus small-molecule drug and rolling circle amplification (RCA) primer are competitively binding with capture probe on the electrode surface through the click chemical reaction. After RCA reaction, methylene blue is used to label the RCA product. In this process, the more Smo on the metastatic cell surface, the more RCA primer is bound with peptide on the electrode. Therefore, the obtained signal response is positively correlated to Smo on the cancer cells. Moreover, the RCA provides sufficiently high sensitivity, enabling the limit of detection of Smo to be calculated as 0.1 pM (〈em〉S〈/em〉/〈em〉N〈/em〉 = 3). Owing to its desirable sensitivity, excellent reproducibility, and high selectivity, the proposed method may hold great potential in clinical practice in the future.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1950_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The abnormal concentration of lysozyme in body fluids and tissues is a potential indicator for diseases such as leukemia and meningitis. In this work, by combining the excellent optical properties of carbon dots (CDs) with the favorable selectivity of molecularly imprinted polymer (MIP), a novel fluorescent probe for lysozyme detection and cell imaging was constructed, where silanized CDs with low cytotoxicity (CDs/SiO〈sub〉2〈/sub〉) were used as the fluorescence signal reporter and 〈em〉N〈/em〉-isopropylacrylamide (NIPAM) was used as the temperature-sensitive monomer. The as-prepared CDs/SiO〈sub〉2〈/sub〉/MIP showed a thermo-sensitive property for the response to lysozyme. Moreover, this probe could be used for quantitative detection of lysozyme, with a wider detection range (0.001~0.01 mg/mL), a low detection limit (0.55 μg/mL), and a high selectivity. Importantly, the MTT assay testified that the fluorescent CDs/SiO〈sub〉2〈/sub〉/MIP probe had low cytotoxicity. In addition, human hepatoma carcinoma cells (HepG-2 cells) could be stained by the CDs/SiO〈sub〉2〈/sub〉/MIP, and showed a bright intracellular green fluorescence, indicating that the imaging of live cells was possible. This study provides a new way to detect lysozyme in vitro and an attractive perspective to probe intracellular lysozyme in vivo.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Singlet oxygen (〈sup〉1〈/sup〉O〈sub〉2〈/sub〉) is the focus of study in many fields, including phototoxicity, antioxidant activity, pollutant weathering, photodynamic therapy, and water disinfection. The imidazole plus RNO (Imd/RNO) method, originated by Kraljic and El Mohsni, is commonly used to monitor singlet oxygen production. In this method, 〈sup〉1〈/sup〉O〈sub〉2〈/sub〉 is quenched by an acceptor, imidazole (Imd), during the formation of a trans-annular peroxide intermediate that bleaches the sensor, p-nitrosodimethylaniline (RNO). Though the method has been widely used, including to monitor 〈sup〉1〈/sup〉O〈sub〉2〈/sub〉 production in complex environments, such as surfactants and cells, studies reporting the efficiency of the assay in complex solvents have not been reported. In this research, the Imd/RNO method in complex, biorelevant solvents, i.e., sodium dodecyl sulfate, octanol, and phosphate buffer-saturated octanol, was compared with reference solvents, i.e., phosphate buffer, ethanol, and methanol, for monitoring 〈sup〉1〈/sup〉O〈sub〉2〈/sub〉 produced by Rose Bengal photosensitization using time-resolved, broadband UV–Vis absorbance measurements. Rates of sensor bleaching and sensitizer photodegradation were simultaneously monitored in each solvent to investigate correlations between the disappearance rates of sensor and sensitizer. The quantum yields of 〈sup〉1〈/sup〉O〈sub〉2〈/sub〉 production (〈em〉ϕ〈/em〉〈sub〉〈em〉∆〈/em〉〈/sub〉) in each solvent were calculated using a relative actinometric method. The dependence of sensor bleaching and sensitizer degradation on acceptor concentration and solvent polarity, and the results of assay controls suggest mechanistic differences underlying the reactions comprising the Imd/RNO method. These results demonstrate the need for caution and controls when using the method in complex samples including those containing cells, tissues, or nanoscale particles.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Helicobacter pylori〈/em〉 (〈em〉H. pylori〈/em〉) infection is the main cause of gastric inflammation and peptic ulcer disease. Diagnosis and treatment are important to prevent these outcomes. The diagnosis of 〈em〉H. pylori〈/em〉 infection can be performed by non-invasive methods, such as 〈sup〉13〈/sup〉C-urea breath test (〈sup〉13〈/sup〉C-UBT). As endogenous urea is normally released to body cavities, we sought to investigate the usefulness of UBT without 〈sup〉13〈/sup〉C-labelled external urea to detect 〈em〉H. pylori〈/em〉 infection. The analysis was performed in a series of adult patients just before upper gastrointestinal endoscopy and biopsy to investigate dyspeptic symptoms. Breath samples were analyzed using isotope ratio mass spectrometry (IRMS). The natural variation of 〈sup〉13〈/sup〉C and 〈sup〉18〈/sup〉O isotopic abundance in the breath samples was also investigated. The results of the isotopic analysis were compared with the findings of the histopathological evaluation of gastric biopsies, which is the gold standard to detect 〈em〉H. pylori〈/em〉 infection. No differences between patients with or without 〈em〉H. pylori〈/em〉 infection could be detected by the isotope analysis of breath tests without 〈sup〉13〈/sup〉C-urea. Therefore, our results showed that UBT without 〈sup〉13〈/sup〉C-urea, analyzed by IRMS, was not useful to detect 〈em〉H. pylori〈/em〉 infection in the study population.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A novel voltammetric method was developed for brimonidine (BRIM) determination in deproteinized aqueous humor, simplifying preparation of biological samples for analysis for stability studies. The differential pulse voltammetric (DPV) method using boron doped diamond electrode (BDDE), based on characteristic oxidation peaks, was proposed and successfully applied. The linearity range was within 5.0 × 10〈sup〉−6〈/sup〉 to 5.0 × 10〈sup〉−5〈/sup〉 M of brimonidine, and limit of detection and limit of quantitation were 1.94 × 10〈sup〉−6〈/sup〉 M and 6.46 × 10〈sup〉−6〈/sup〉 M, respectively. Intra-day and inter-day precision and accuracy were evaluated and all results were in accordance with validation ICH guidelines. The best short-term stability study results were obtained for a concentration level of 3.0 × 10〈sup〉−5〈/sup〉 M expressed by deviation of + 1.86% between initial and post storage concentrations. A long-term stability study was performed for two concentrations of 3.0 × 10〈sup〉−5〈/sup〉 M and 5.0 × 10〈sup〉−5〈/sup〉 M and resulted in deviations of + 1.63% and + 3.56%, respectively. A freeze and thaw stability study indicated that samples might be frozen only once. The enhancement of DPV/BDDE method sensitivity gained by modification, for the analysis of immeasurable BRIM quantities in native, untreated aqueous humor, was reached for quantities of 6 or 12 nmol/0.1 mL aqueous humor with acceptable accuracy (up to + 7.5%). The nature of the process—the irreversible one electron oxidation voltammetric peak of BRIM—limited the sensitivity. Only electrochemical pre-treatment of the BDD electrode before each measurement significantly speeded up the whole procedure. The advantages of the proposed method are simplicity, short-time performance, and good specificity/selectivity, as well as satisfactory accuracy, and no chemical modification of BDDE was necessary.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this work, dried flowers of 〈em〉Osmanthus fragrans〈/em〉 Lour. were applied as green precursors to synthesize carbon dots (CDs) by a green hydrothermal method for the first time. The CDs showed strong blue fluorescence at 410 nm under 340-nm excitation with a quantum yield of approximately 18.53%. Furthermore, the CDs were applied for the sensitive detection of Fe〈sup〉3+〈/sup〉. The linear response of Fe〈sup〉3+〈/sup〉 ranged from 10 nM to 50 μM with a limit of detection as low as 5 nM. In addition, other ions were used as competitive substances to explore the selectivity of CDs for Fe〈sup〉3+〈/sup〉. The fluorescence quenching effect of Fe〈sup〉3+〈/sup〉 was much stronger, which demonstrated that the CDs had high selectivity for Fe〈sup〉3+〈/sup〉 and they can be employed for the selective detection of Fe〈sup〉3+〈/sup〉. The potential fluorescence quenching mechanism between CDs and Fe〈sup〉3+〈/sup〉 was identified as the inner filter effect. The CDs were then used as a fluorescent sensor for the detection of Fe〈sup〉3+〈/sup〉 in water samples and human serum; the recovery range was 93.76–113.80% (relative standard deviation less than 0.79%). These results indicate that the CDs can be applied for the sensitive and selective detection of Fe〈sup〉3+〈/sup〉 in real samples. Moreover, on the basis of the redox reaction between Fe〈sup〉3+〈/sup〉 and ascorbic acid (AA), the CD–Fe〈sup〉3+〈/sup〉 system can be used as a fluorescent “off–on” sensor for the detection of AA with a limit of detection of 5 μM. What is more, because of their low toxicity and biocompatibility, the CDs can also be used for cell imaging and acted as a fluorescent probe for fluorescence imaging of Fe〈sup〉3+〈/sup〉 and AA in living cells. These results demonstrate that the CDs have great potential for application in the fields of sensing, bioimaging, and even disease diagnosis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, a magnetic molecular sieve material (Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@MCM-48) was synthesized by a combination of solvothermal and self-assembly methods. The physicochemical properties of the magnetic molecular sieve material were characterized by scanning electron microscopy, energy-dispersive spectroscopy, magnetic hysteresis loop measurements, transmission electron microscopy, powder X-ray diffraction, N〈sub〉2〈/sub〉 adsorption–desorption analysis, and Fourier transform infrared spectroscopy. The as-synthesized nanocomposite showed various advantages, including easy magnetic-assisted separation, high specific surface area, and a highly interwoven and branched mesoporous structure. The Fe〈sub〉3〈/sub〉O〈sub〉4〈/sub〉@MCM-48 nanocomposite was then used as an effective adsorbent material for magnetic solid-phase extraction of fluoroquinolones (FQs) from water samples. The FQs in the extract were determined via liquid chromatography–tandem mass spectrometry. Adsorption and desorption factors that affected the extraction performance were systematically optimized using spiked purified water samples. Good linearity (with 〈em〉R〈/em〉〈sup〉2〈/sup〉 〉 0.99) was shown by this FQ detection system for FQ concentrations from 5 to 1000 ng L〈sup〉−1〈/sup〉. Moreover, low detection limits (0.7–6.0 ng L〈sup〉−1〈/sup〉) and quantitation limits (2.5–20.0 ng L〈sup〉−1〈/sup〉) and satisfactory repeatability (relative standard deviation 〈 10%, 〈em〉n〈/em〉 = 6) were achieved for water samples. The developed method was also validated for the analysis of FQs in meat and milk samples. Finally, FQs in food and drinking water samples were successfully determined using the developed method.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1726_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈p〉The authors would like to call the reader’s attention to the fact that unfortunately the formula for the O17 correction parameter “a” is reported incorrectly as.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Enzyme-mimicking (nanozyme)-based biosensors are attractive owing to their unique catalytic efficiency, multifunctionality, and tunable activity, but examples of oxidase-like nanozymes are quite rare. Herein, we demonstrated that histidine-capped gold nanoclusters (His@AuNCs) possessed intrinsic oxidase-like activity, which could directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) to blue colored ox-TMB without H〈sub〉2〈/sub〉O〈sub〉2〈/sub〉. The assembly of reduced graphene oxide (RGO) with His@AuNCs could further improve its oxidase-like activity and the His@AuNCs/RGO nanocomposites had a lower Michaelis constant (〈em〉K〈/em〉〈sub〉m〈/sub〉) and higher catalytic constant (〈em〉K〈/em〉〈sub〉cat〈/sub〉) for TMB oxidation. Furthermore, compared to other nanomaterials, the as-prepared His@AuNCs/RGO also exhibited enhanced electrocatalytic activity toward TMB. Interestingly, nitrite inhibited the catalytic (chromogenic) and electrocatalytic processes of His@AuNCs/RGO in the oxidation of TMB. The oxidase-like and electrocatalytic activity of His@AuNCs/RGO was evaluated with nitrite and TMB as substrates, and the results indicated that TMB and nitrite might share the same catalytic active sites. On the basis of these findings, a colorimetric and electrochemical sensor was developed with the His@AuNCs/RGO composite as an oxidase mimic for determination of nitrite with linear ranges of 10–500 μM and 2.5–5700 μM, respectively. The developed method was successfully applied to the detection of nitrites in real samples. The present work suggests that the oxidase-like nanozyme is not only suitable for colorimetric assay but also for development of electrochemical sensors in bioanalysis.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉The colorimetric and electrochemical detection of nitrite using His@AuNCs/RGO.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1655_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Today, bottom-up protein identification in MALDI-MS is based on employing singly charged peptide ions, which are predominantly formed in the ionization process. However, peptide mass fingerprinting (PMF) with subsequent tandem MS confirmation using these peptide ions is often hampered due to the lower quality of fragment ion mass spectra caused by the higher collision energy necessary for fragmenting singly protonated peptides. Accordingly, peptide ions of higher charge states would be of high interest for analytical purposes, but they are usually not detected in MALDI-MS experiments as they overlap with singly charged matrix clusters and peptide ions. However, when utilizing ion mobility spectrometry (IMS), doubly charged peptide ions can be actively used by separating them from the singly protonated peptides, visualized, and selectively targeted for tandem MS experiments. The generated peptide fragment ion spectra can be used for a more confident protein identification using PMF with tandem MS confirmation, as most doubly protonated peptide ions yield fragment ion mass spectra of higher quality compared to tandem mass spectra of the corresponding singly protonated precursor ions. Mascot protein scores can be increased by approximately 50% when using tandem mass spectra of doubly charged peptide ions, with ion scores up to six times higher compared with ion scores of tandem mass spectra from singly charged precursors.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Here we report a bacteria detection method based on a flow cytometric bead system and 16S rRNA-targeted oligonucleotide probes. Polymerase chain reaction (PCR) was first used to acquire bacterial DNA including bacteria-specific sequences. Half of the resulting target DNA was then captured by a capture probe immobilized on a magnetic microbead (MB) surface. The other half of the target DNA was hybridized with a fluorescence-labeled signal probe. In this manner, a sandwich DNA hybridization involving a MB-based capture probe, the target DNA, and a signal probe was realized. The MB carriers modified with reporter dye were analyzed one by one by flow cytometry through a capillary. Using PCR amplicons and this flow cytometric bead system, a detection limit of 180 cfu mL〈sup〉−1〈/sup〉 was achieved, along with high selectivity that permitted the discrimination of different targets when challenged with control bacteria targets and multiplexing capabilities that enabled the simultaneous detection of two kinds of bacteria. Given these advantages, the developed method can be used for the highly sensitive and specific PCR amplicon analysis of DNA extracted from a fresh bacterial culture, as well as multiplex target analysis.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉The flow cytometric bead system with 16S rRNA-targeted oligonucleotide probes for bacteria detection developed in this work. This system is highly specific and sensitive, with a detection limit of 180 cfu mL〈sup〉−1〈/sup〉 bacteria.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1651_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Cell-penetrating peptides (CPPs) have garnered significant attention as a method to introduce reporters and therapeutics into intact cells. While numerous studies have been performed identifying new CPP sequences, relatively little is known about their uptake efficiency at the single-cell level. Here, a droplet microfluidic trapping array was used to characterize CPP uptake across a population of single intact cells. The microfluidic device allowed for facile and rapid isolation and analysis of single-cell fluorescence in a 787-member overhead trapping array with 〉 99% droplet trapping efficiency. The permeability efficiencies of four different CPPs were studied and compared in HeLa cells. Population analysis was performed using linkage hierarchical cluster analysis by R programming to bin cells into subpopulations expressing very low to very high peptide uptake efficiencies. CPP uptake was observed to be heterogeneous across the population of cells with peptide concentration and sequence both playing important roles in the diversity of CPP uptake, the overall peptide uptake efficiency, and the intracellular homogeneity of peptide distribution. This microfluidic-based analytical approach finds application in personalized medicine and provides new insight in the heterogeneity of CPP uptake which has the potential to affect both biosensor and drug internalization in intact cells.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉.〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1713_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉〈em〉Crataegus〈/em〉 products for food, nutritional, and pharmaceutical uses are available over the counter in the global market. The aerial parts are enriched with biochemicals and are used to treat cardiovascular, respiratory, and liver disorders and cancer. Detailed study to understand the chemical composition and different levels within medicinally important plant tissues needs hours, such as plant response for metabolite flux and quality control purposes. Therefore, comprehensive metabolite profiling (qualitatively and quantitatively) of different tissues [leaves, flowers, stems, fruits (without seeds), and seeds; 〈em〉n〈/em〉 = 5] of 〈em〉Crataegus rhipidophylla〈/em〉 Gand〈em〉.〈/em〉 was performed by NMR techniques in one session. Fifty-eight compounds of different classes were unambiguously identified with the use of 1D and 2D NMR techniques (〈sup〉1〈/sup〉H, 〈sup〉13〈/sup〉C, distortionless enhancement by polarization transfer with 135° angle, correlation spectroscopy, heteronuclear single quantum coherence, heteronuclear multiple bond correlation) and quantified by a relative quantification method. Chemical compounds such as amygdalin (seeds), rutin (flowers), isovitexin (fruits), shikimic acid (leaves), and epicatechin (stems) were identified as authentication as well as discrimination markers for the respective 〈em〉C. rhipidophylla〈/em〉 tissues〈em〉.〈/em〉 The fruits contain a significant mixture of important metabolites, followed by flowers and leaves. Trends of metabolite levels, upregulation, and downregulation in plant tissues were found, which highlights the responses of plant tissues in a specific time. NMR-based comprehensive metabolite information was used to develop the chemical signature, quality control chemical markers, and strategies to understand the chemical diversity of 〈em〉C. rhipidophylla.〈/em〉 This chemical information from different aerial tissues will provide guidance for the extensive utilization of 〈em〉Crataegus〈/em〉.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1646_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The scientific interest in gas sensors is continuously increasing because of their environmental, medical, industrial, and domestic applications. This has resulted in an increasing number of investigations being reported in the literature and communicated at conferences. The present review, organized in two parts, addresses the peculiarities of gas sensors based on mass-sensitive transducers, starting with their structure and functionality and progressing to implementation and specific use. In this first part of the review, we discuss the constructional peculiarities and operation regions and the physical and chemical processes governing the reception and transduction functions and the way in which they influence the sensor sensing parameters/features. Scientific outcomes and trends in research into gas sensors based on mass sensitive transducers are also considered.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The present work is aimed to develop a simple, rapid, and cost-effective CE method for the determination of trimethylamine (TMA) from bacterial origin. Optimum separation of TMA from the other components of the bacterial culture was achieved using a fused silica capillary (27 cm × 75 μm ID) and a background electrolyte solution that consisted of 0.75 M formic acid at pH 2.05. Analytical characteristics of the proposed method were evaluated through the study of its specificity, linearity, precision, accuracy, robustness, and detection/quantitation limit values. The method was linear over the range 25–2000 μM (〈em〉R〈/em〉〈sup〉2〈/sup〉 = 0.9998). The LOD and LOQ were 9 μM and 27 μM, respectively. Intra-day and inter-day RSD were ≤ 0.24% and ≤ 1.3% for migration time, respectively. Intra-day and inter-day RSD for peak area were ≤ 2.44% and ≤ 3.51%, respectively. The method showed a good accuracy with recovery percentages ranging from 95.45 to 102.21%. The method was successfully applied for the determination of microbial conversion of 〈span〉l〈/span〉-carnitine to TMA. The method shows great potential in high-throughput screening applications to assess the functionality of the gut microbiota to produce TMA.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1716_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In the past, the main focus of flame ionization detector (FID) response studies was set on investigations of gas chromatography (GC) relevant analytes such as aliphatic hydrocarbons and selected functional groups. Only a few data are available for liquid chromatography (LC)/FID responses. Within this research paper, we present the FID response factors for a LC/FID system with an aqueous eluent as mobile phase. The study focus on the most common analytes of LC/FID studies in the past as well as several compounds that are not directly GC compatible because of their polarity. Furthermore, the range of substances was extended to isomers, poly-alcohols, and sugars to obtain more detailed information of the influence of hydroxyl groups on the recorded response. The data show a group-specific correlation of response factors with a correlation coefficient (〈em〉R〈/em〉〈sup〉2〈/sup〉) for, e.g., alcohols and ketones of 0.99. Constant contribution factors of functional groups as mentioned in several GC/FID response studies and prediction models were observed to a limited extent. Interactions of sugar analytes with water showed that transfer of GC/FID to LC/FID data cannot be done in general. The underlying mechanisms revealed several new aspects, which have to be taken into account for future response prediction models, especially of small molecules. Interactions between eluent and analytes show that LC/FID response prediction is more complex and requires more than simple addition of functional group contributions.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉With the number of approved biosimilars rapidly increasing in the various regulatory jurisdictions, public perception of safety and efficacy of these products have been gradually improving. Establishment of analytical similarity with the innovator product is a key aspect of biosimilar development. It serves as the basis for reduction in the size and/or scope of clinical trials. However, the clinical performance must be consistent with the innovator product. A considerable amount of effort precedes this exercise and requires a suitable reference material to support analytical method development. In view of the high cost as well as limited availability of innovator product in the market, there is a need for suitable reference material which could serve this purpose. The National Institute of Standards and Technology (NIST) have recently created NIST monoclonal antibody (NISTmAb) to support analytical method development and commercialization of monoclonal antibody-based biotherapeutics. In this paper, it is intended to evaluate lifecycle appropriate implementation of NISTmAb, a class-specific reference material in biosimilar analytical development. The results show that NISTmAb can be useful in developing initial platform analytical methods and as an external control for class-specific products. However, as expected, it cannot replace an innovator product or in-house product-specific reference material for analytical similarity assessment. As per regulatory guideline, a product-specific optimization will continue to be a prerequisite for specific analytical properties.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The quantity and activity of proteins in many biological systems exhibit prominent heterogeneities. Single-cell analytical methods can resolve subpopulations and dissect their unique signatures from heterogeneous samples, enabling a clarifying view of the biological process. Over the last 5 years, technologies for single-cell protein analysis have significantly advanced. In this article, we highlight a branch of those technology developments involving fluorescence-based approaches, with a focus on the methods that increase the ability to multiplex and enable dynamic measurements. We also analyze the limitations of these techniques and discuss current challenges in the field, with the hope that more transformative platforms can soon emerge.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Vacuum-assisted evaporative concentration (VEC) was successfully applied and validated for the enrichment of 590 organic substances from river water and wastewater. Different volumes of water samples (6 mL wastewater influent, 15 mL wastewater effluent, and 60 mL river water) were evaporated to 0.3 mL and finally adjusted to 0.4 mL. 0.1 mL of the concentrate were injected into a polar reversed-phase C18 liquid chromatography column coupled with electrospray ionization to high-resolution tandem mass spectrometry. Analyte recoveries were determined for VEC and compared against a mixed-bed multilayer solid-phase extraction (SPE). Both approaches performed equally well (≥ 70% recovery) for a vast number of analytes (〈em〉n〈/em〉 = 327), whereas certain substances were especially amenable to enrichment by either SPE (e.g., 4-chlorobenzophenone, log〈em〉D〈/em〉〈sub〉ow,pH7〈/sub〉 4) or VEC (e.g., TRIS, log〈em〉D〈/em〉〈sub〉ow,pH7〈/sub〉 − 4.6). Overall, VEC was more suitable for the enrichment of polar analytes, albeit considerable signal suppression (up to 74% in river water) was observed for the VEC-enriched sample matrix. Nevertheless, VEC allowed for accurate and precise quantification down to the sub-nanogram per liter level and required no more than 60 mL of the sample, as demonstrated by its application to several environmental water matrices. By contrast, SPE is typically constrained by high sample volumes ranging from 100 mL (wastewater influent) to 1000 mL (river water). The developed VEC workflow not only requires low labor cost and minimum supervision but is also a rapid, convenient, and environmentally safe alternative to SPE and highly suitable for target and non-target analysis.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1696_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Metabolomics quantitatively measures metabolites in a given biological system and facilitates the understanding of physiological and pathological activities. With the recent advancement of mass spectrometry (MS) technology, liquid chromatography-mass spectrometry (LC-MS) with data-independent acquisition (DIA) has been emerged as a powerful technology for untargeted metabolomics due to its capability to acquire all MS2 spectra and high quantitative accuracy. In this trend article, we first introduced the basic principles of several common DIA techniques including MS〈sup〉E〈/sup〉, all ion fragmentation (AIF), SWATH, and MSX. Then, we summarized and compared the data analysis strategies to process DIA-based untargeted metabolomics data, including metabolite identification and quantification. We think the advantages of the DIA technique will enable its broad application in untargeted metabolomics.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Polymerase chain reaction (PCR) is a powerful technique for the detection and quantification of nucleic acids and has enormous applications to research in molecular biology. Certain inherited diseases, caused by single nucleotide mutations, however, are difficult to identify by PCR, using DNA primers and probes, in a situation where a false diagnosis may lead to incorrect or delayed treatment. With the aim of enhancing the specificity of PCR, we used novel chemically synthesized oligonucleotides containing site-specific methyl phosphotriester (MPTE) inter-nucleoside linkage(s) as primers and probes. The methyl phosphotriester linkages carry no charge, so the reduction in the electrostatic repulsion of an MPTE-DNA/DNA duplex shows stronger hybridization affinity compared to a DNA/DNA duplex. However, the electrosteric effects introduced by the methyl group may result in instability of the double-stranded DNA (dsDNA) formed. With the use of specific MPTE modification sites and optimization of the number of MPTE modifications, greater delta melting temperature (ΔT〈sub〉m〈/sub〉) may be obtained, in concert with adjustment of PCR operating conditions, especially with respect to the annealing temperature, to achieve more discriminatory results between the target template and the perfectly matched primer and the mismatched primer. In single nucleotide polymorphism (SNP) genotyping, the results demonstrated that MPTE-modified probes can improve specificity. In summary, MPTE-modified oligonucleotides are a promising DNA analog applied to PCR primers and probes to enhance the specificity and to provide more precise detection results for various applications, such as for genetic diagnosis. In summary, two common DNA polymerases we tested could successfully recognize the MPTE-modified primers and probes. Under the optimal operating conditions, MPTE modification has the ability to improve the discrimination of single nucleotide polymorphism by increasing the ΔT〈sub〉m〈/sub〉 of the perfect match and mismatch sequences and to provide more precise detection results for various applications, such as genetic diagnosis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A novel method was developed and validated for the quantification of the three approved CDK4/6 inhibitors (abemaciclib, palbociclib, and ribociclib) in both human and mouse plasma and mouse tissue homogenates (liver, kidney, spleen, brain, and small intestine) using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). For all matrices, pretreatment was performed using 50 μL of sample by protein precipitation with acetonitrile, followed by dilution of the supernatant. Chromatographic separation of the analytes was done on a C18 column using gradient elution. A full validation was performed for human plasma, while a partial validation was executed for mouse plasma and mouse tissue homogenates. The method was linear in the calibration range from 2 to 200 ng/mL, with a correlation coefficient (〈em〉r〈/em〉) ≥0.996 for each analyte. For both human and mouse plasma, the accuracy and precision were within ±15% and ≤15%, respectively, for all concentrations, except for the lower limit of quantification, where they were within ±20% and ≤20%, respectively. A fit-for-purpose strategy was followed for tissue homogenates, and the accuracy and precision were within ±20% and ≤20%, respectively, for all concentrations. Stability of all analytes in all matrices at different processing and storage conditions was tested; ribociclib and palbociclib were unstable in most tissue homogenates and conditions were modified to increase the stability. The method was successfully applied for the analysis of mouse samples from preclinical studies. A new ribociclib metabolite was detected in mouse plasma samples with the same 〈em〉m/z〈/em〉 transition as the parent drug.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Surface-enhanced Raman spectroscopy (SERS) method based on gold nanoparticles as SERS substrate was investigated for the label-free detection and quantification of probiotic bacteria that are widely used in various pharmaceutical formulations. Indeed, the development of a simple and fast SERS method dedicated to the quantification of bacteria should be very useful for the characterization of such formulations in a more convenient way than the usually performed tedious and time-consuming conventional counting method. For this purpose, uncoated near-spherical gold nanoparticles were developed at room temperature by acidic treatment of star-like gold nanoparticle precursors. In this study, we first investigated the influence of acidic treatment conditions on both the nanoparticle physicochemical properties and SERS efficiency using Rhodamine 6G (R6G) as “model” analyte. Results highlighted that an effective R6G Raman signal enhancement was obtained by promoting chemical effect through R6G-anion interactions and by obtaining a suitable aggregation state of the nanoparticles. Depending on the nanoparticle synthesis conditions, R6G SERS signals were up to 10〈sup〉2〈/sup〉–10〈sup〉3〈/sup〉-fold greater than those obtained with star-like gold nanoparticles. The synthesized spherical gold nanoparticles were then successfully applied for the detection and quantification of 〈em〉Lactobacillus rhamnosus GG〈/em〉 (LGG). In that case, the signal enhancement was especially due to the combination of anion-induced chemical enhancement and nanoparticle aggregation on LGG cell wall consecutive to non-specific interactions. Both the simplicity and speed of the procedure, achieved under 30 min, including nanoparticle synthesis, sample preparation, and acquisition of SERS spectra, appeared as very relevant for the characterization of pharmaceutical formulations incorporating probiotics.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1938_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We report here a novel approach for the extraction and analysis of thyroid hormones (TH) and their metabolites (THM) from human serum samples. Our method features a compact, 96-well micro-titre plate-based pre-analytic extraction/clean-up workflow combined with an isotope dilution LC-MS/MS-MS〈sup〉3〈/sup〉 analytical method. In particular, these features make possible the detection of iodothyronines at their endogenous concentrations in serum differing by a factor of ca. 10〈sup〉4〈/sup〉, with potential to semi-automate the pre-analytics. The method was validated by the assessment of linearity, lower limits of quantification and detection (LLOQ and LLOD respectively), intra- and inter-day accuracy, precision, process efficiency (PE), matrix effect (ME) and relative recovery (RE). Calibration curves were linear in the concentration range in sample matrix from 0.1–250 nM for T〈sub〉3〈/sub〉, rT〈sub〉3〈/sub〉, T〈sub〉4〈/sub〉 and 3-T〈sub〉1〈/sub〉AM and from 0.005–1 nM for 3,5-T〈sub〉2〈/sub〉 and 3,3′-T〈sub〉2〈/sub〉. Using a 200-μL sample volume, the analyte dependant LLOQ were in the range 0.005 (3,5-T〈sub〉2〈/sub〉) to 0.25 (T〈sub〉4〈/sub〉) nM and LLOD were between 0.002 (3,5-T〈sub〉2〈/sub〉) and 0.052 nM (T〈sub〉4〈/sub〉). We applied the LC-MS/MS-MS〈sup〉3〈/sup〉 method to the analysis of a cross section of patients with disorders of the thyroid hormone axis. T〈sub〉4〈/sub〉, T〈sub〉3〈/sub〉 and rT〈sub〉3〈/sub〉 concentrations (± standard deviation) were 120 ± 18, 1.9 ± 0.4 and 0.45 ± 0.09 nM respectively. 3,3′-T〈sub〉2〈/sub〉 concentrations (± standard deviation) were 0.079 ± 0.022 nM; 3,5-T〈sub〉2〈/sub〉 concentrations were below the LLOQ and/or LLOD in all but a single sample (0.013 nM). This method expands the analytical spectrum to endogenous thyroid hormone metabolites such as 3,5-T〈sub〉2〈/sub〉 which exert biological actions and rT〈sub〉3〈/sub〉 which may act as surrogate markers for disturbed thyroid hormone metabolism.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1941_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉While the targeted analysis of mercapturic acid (MA) metabolites in human urine is used to assess exposure to selected chemicals, this compound class has only rarely been addressed in non-target screening utilizing diagnostic neutral loss liquid chromatography tandem mass spectrometry (LC-MS/MS). Additionally, this type of analysis is severely affected by matrix effects (MEs) causing poor comparability of samples and distortion of signal intensities. However, MEs have been neglected in urinary MA non-target screening so far. Therefore, we developed a non-target screening method relying on neutral loss scanning for MAs using post column infusion of an isotope-labelled standard. For signal correction, we synthesized a structural analogue to MAs, 〈em〉N〈/em〉-acetyl-〈em〉S〈/em〉-methyl-homocysteine-D〈sub〉3〈/sub〉, lacking the characteristic neutral loss of the MAs. For method development, 16 structurally different model MA compounds and 20 spiked urine samples were used. Twelve out of the 16 model compounds could be analysed by the developed method. We found severe matrix effects (largely signal suppression) for the spiked model compounds, with only 34% of all peaks’ intensities changing by less than a factor of two. This could be compensated by the post column internal standard infusion with now 68% of all peaks’ intensities changing by less than a factor of two. For three compounds, an over-compensation was observed resulting in an increase of signal of up to a factor of 16. In the 20 urine samples, altogether 558 native MAs (between 74 and 175 per sample) could be detected after ME compensation. These results indicate that a large number of so far uncharacterized MAs are present in urine, which yield a potential for biomarker discovery and pattern characterisation.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical Abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2166_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Alkaline phosphatase (ALP) is an important enzyme that is associated with many human diseases, so the quantitative detection of ALP is vital from a clinical perspective. Nevertheless, most fluorescent assays for monitoring ALP depend on aggregation-induced quenching (ACQ), single-signal modulation, or a “signal off” mode, which suffer from poor sensitivity, a “false positive” problem, and low signal output. In this work, we utilized the electrostatically driven self-assembly of glutathione-capped gold nanoclusters (GSH-AuNCs, which show aggregation-induced emission, AIE) and amino-modified silicon nanoparticles (SiNPs) to create a hybrid probe (SiNPs@GSH-AuNCs). This nanohybrid probe showed emission from the SiNPs at around 470 nm as well as aggregation-induced emission enhancement (AIEE) of the GSH-AuNCs at 580 nm. The AIEE of the GSH-AuNCs was quenched in the presence of KMnO〈sub〉4〈/sub〉, but the AIEE was recovered by adding ascorbic acid as an oxidation–reduction reaction occurred between KMnO〈sub〉4〈/sub〉 and the ascorbic acid. The fluorescence of the SiNPs remained constant whether the AIEE was quenched or not, meaning that the fluorescence of the SiNPs could be used as an internal reference. In a typical enzymatic reaction, ascorbic acid 2-phosphate is hydrolyzed by ALP to produce ascorbic acid. Therefore, the hybrid probe was shown to allow the ratiometric detection of ALP, with a linear range of 0.5–10 U L〈sup〉−1〈/sup〉 and a limit of detection (LOD) of 0.23 U L〈sup〉−1〈/sup〉. Finally, the proposed analytical strategy was successfully applied to detect ALP in human serum samples and to determine the concentration of an ALP inhibitor.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical Abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2098_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A new class of magnetic ionic liquids (MILs) with metal-containing cations was applied in in situ dispersive liquid–liquid microextraction (DLLME) for the extraction of long and short double-stranded DNA. For developing the method, MILs comprised of N-substituted imidazole ligands (with butyl-, benzyl-, or octyl-groups as substituents) coordinated to different metal centers (Ni〈sup〉2+〈/sup〉, Mn〈sup〉2+〈/sup〉, or Co〈sup〉2+〈/sup〉) as cations, and chloride anions were investigated. These water-soluble MILs were reacted with the bis[(trifluoromethyl)sulfonyl]imide anion during the extraction to generate a water-immiscible MIL capable of preconcentrating DNA. The feasibility of combining the extraction methodology with anion-exchange high-performance liquid chromatography with diode array detection (HPLC-DAD) or fluorescence spectroscopy was studied. The method with the Ni〈sup〉2+〈/sup〉- and Co〈sup〉2+〈/sup〉-based MILs was easily combined with fluorescence spectroscopy and provided a faster and more sensitive method than HPLC-DAD for the determination of DNA. In addition, the method was compared to conventional DLLME using analogous water-immiscible MILs. The developed in situ MIL-DLLME method required only 3 min for DNA extraction and yielded 1.1–1.5 times higher extraction efficiency (EFs) than the conventional MIL-DLLME method. The in situ MIL-DLLME method was also compared to the trihexyl(tetradecyl)phosphonium tris(hexafluorocetylaceto)nickelate(II) MIL, which has been used in previous DNA extraction studies. EFs of 42–99% were obtained using the new generation of MILs, whereas EFs of only 20–38% were achieved with the phosphonium MIL. This new class of MILs is simple and inexpensive to prepare. In addition, the MILs present operational advantages such as easier manipulation in comparison to hydrophobic MILs, which can have high viscosities. These MILs are a promising new class of DNA extraction solvents that can be manipulated using an external magnetic field.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉Magnetic ionic liquids with metal-containing cations are applied in in situ dispersive liquid–liquid microextraction for the extraction of long and short double-stranded DNA〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_2163_Fige_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The origin of the method of standard additions (SAM) and of the use of internal standard (IS) in instrumental chemical analysis and their spread into other areas has been reviewed. Recorded applications of IS range from flame spectroscopy in 1877 through multiple techniques to current use in NMR and standard additions with isotopically labelled internal standards in hyphenated techniques. For SAM, applications stemmed from polarography in 1937 and spread to most instrumental methods. Some misconceptions on priorities are corrected.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Differential mobility spectrometry (DMS) has been gaining popularity in small molecule analysis over the last few years due to its selectivity towards a variety of isomeric compounds. While DMS has been utilized in targeted liquid chromatography-mass spectrometry (LC-MS), its use in untargeted discovery workflows has not been systematically explored. In this contribution, we propose a novel workflow for untargeted metabolomics based solely on DMS separation in a clinically relevant chronic kidney disease (CKD) patient population. We analyzed ten plasma samples from early- and late-stage CKD patients. Peak finding, alignment, and filtering steps performed on the DMS-MS data yielded a list of 881 metabolic features (unique mass-to-charge and migration time combinations). Differential analysis by CKD patient group revealed three main features of interest. One of them was putatively identified as bilirubin based on high-accuracy MS data and comparison of its optimum compensation voltage (COV) with that of an authentic standard. The DMS-MS analysis was four times faster than a typical HPLC-MS run, which suggests a potential for the utilization of this technique in screening studies. However, its lower separation efficiency and reduced signal intensity make it less suitable for low-abundant features. Fewer features were detected by the DMS-based platform compared with an HPLC-MS-based approach, but importantly, the two approaches resulted in different features. This indicates a high degree of orthogonality between HPLC- and DMS-based approaches and demonstrates the need for larger studies comparing the two techniques. The workflow described here can be adapted for other areas of metabolomics and has a value as a prescreening method to develop semi-targeted workflows and as a faster alternative to HPLC in large biomedical studies.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1719_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The baseline instability for capillary electrophoretic analysis is an intrinsic feature of the technique, which has not been thoroughly examined for its impact on therapeutic protein purity analysis with the capillary electrophoresis-sodium dodecyl sulfate (CE-SDS) applications. For the particular CE-SDS application, this phenomenon was manifested through peak migration time shifts and sliding of the superimposed baseline profile. These dual phenomena are closely associated so that experimental assessment alone may not shed enough light to the underlying drivers. In the current study, both experimental and simulation approaches were employed to assess the systematic drifts. Computer simulation was used to decipher the two underlying factors and test their contributions toward purity and impurity peak determination inaccuracies. The data generated in this study demonstrated that the electrophoretic baseline disturbance had more pronounced impact on the purity data than the migration time shift. In addition, the potential contributing factors to the baseline disturbances were assessed experimentally which indicated that the source is related to thermal disruption during a sample run and the unique baseline patterns came from the background electrolytes. To improve data reproducibility for drug purity testing in the industrial setting and quality control (QC) environment, it is recommended to run shorter injection sequences including fewer samples and closely monitor the baseline drift for accurate integration. Those methods would help reduce the impact of systematic drift and disturbances.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1704_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The Manuguru geothermal area, located in the Telangana state, is one of the least explored geothermal fields in India. In this study, characterization of the soil samples is carried out by laser-induced breakdown spectroscopy (LIBS) coupled with analytical spectral-dependent principal component analysis. A total of 20 soil samples were collected both from near the thermal discharges as well as away from the thermal manifestations. LIBS spectra were recorded for all the collected soil samples and principal component analysis (PCA) was applied to easily identify the emission lines majorly responsible for variety classification of the soil samples. In this submission, a modified PCA was developed which is based on the spectral truncation method to reduce the huge number of spectral data obtained from LIBS. The PCA bi-plot on the LIBS data reveals the presence of two different clusters. One cluster represents the soil samples collected from the close vicinity of the thermal manifestations whereas the other cluster contains the soil samples collected away from the thermal sprouts. PCA performed on the chemical dataset of the soil samples also reveals the same clustering of the soil samples. Both LIBS and chemical analysis data shows that soil samples near the thermal waters are found to be enriched in B, Sr, Cs, Rb, Fe, Co, Al, Si, Ti, Ru, Mn, Mg, Cu, and Eu concentrations compared to the soil samples located away from thermal manifestations. This study demonstrates the potential use of LIBS coupled with PCA as a tool for variety discrimination of soil samples in a geothermal area. LIBS is shown to be a viable real-time elemental characterization technology for these samples, avoiding the rigorous dissolution required by other analytical techniques.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1731_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A solid-phase microextraction (SPME) fiber based on a new polymeric ionic liquid was prepared for the extraction of trace aromatic amines in water and their detection by gas chromatography–mass spectrometry (GC–MS). The newly designed polymeric ionic liquid with two functional groups (benzene ring and ether group) was synthesized and fixed on stainless steel wire to effectively extract aromatic amines. Parameters that affect the extraction efficiency of the SPME fiber (extraction temperature, extraction time, alkali concentration, and salt concentration) were optimized to establish a headspace SPME–GC–MS method. The correlation coefficients were 0.996 or greater for concentration of the aromatic amines ranging from 0.01 to 10 μg mL〈sup〉-1〈/sup〉. In addition, the limits of detection for the new fiber are as low as 0.67 ng mL〈sup〉-1〈/sup〉, which is lower than that obtained with polyacrylate. The relative standard deviations of five consecutive extractions for the solution spiked at 1 μg mL〈sup〉-1〈/sup〉 by the same fiber were all below 8.3%, and the interfiber relative standard deviations for the solution spiked at the same concentration ranged from 8.9% to 15.2%. Furthermore, long lifetime and good solvent resistance are exhibited by the fiber. Finally, satisfactory relative recovery in the range from 85.3% to 101.9 % was achieved for two environmental water samples.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1664_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The aim of this work was to evaluate the evaporation behavior of certain aroma compounds found in e-liquids. Since an e-liquid is evaporated, the aroma present can reach the lungs and could be absorbed into the body which may have long-term health effects above critical concentrations. Due to a lack in regulations, the sort and concentration of the compounds in sold e-liquids can vary. To capture the aroma compounds in the vapor, a smoking machine was developed. The resulting data represent the amount of aroma reaching the consumers’ lungs. The influence of the e-cigarette temperature, ranging from 100 to 315 °C, on the evaporation of benzaldehyde, estragole, and different terpenoids was examined. Additionally, the effect of the liquid base composition on the amount of aroma in the vapor was compared using the analysis of variances. The influence of high temperature, the type of e-cigarette, and the atomizer coil material, which could lead to oxidation of limonene and linalool in the vapor, is shown here.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1749_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A novel and sensitive fluorescent sensor was synthesized for the rapid and specific recognition of aflatoxin B〈sub〉1〈/sub〉 (AFB1) by our combining molecular imprinting techniques with quantum dot technology. Molecularly imprinted polymers coated CdTe quantum dots (MIP@CdTe QDs) were prepared through the Stöber method with 5,7-dimethoxycoumarin as a dummy template. 3-Aminopropyltriethoxysilane was selected as the functional monomer, and tetraethyl orthosilicate was used as the cross-linking agent. The best molar ratio of 5,7-dimethoxycoumarin to functional monomer to cross-linker was 4:20:15. The MIP@CdTe QD composites were characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, and fluorescence spectroscopy. Under the optimum conditions, the relative fluorescence intensity of the MIP@CdTe QDs showed adequate linearity with AFB1 concentration over the range from 80 to 400 ng/g. The detection limit is 4 ng/g, according to 3〈em〉s〈/em〉/〈em〉K.〈/em〉 Finally, the method was successfully applied to the quantitative determination of AFB1 in real samples. The spike recoveries at different spiking levels ranged from 99.20% to 101.78%, which were consistent with those measured by ultrahigh-performance liquid chromatography–mass spectrometry. The method developed for AFB1 detection lays the foundation for rapid detection of trace amounts of other exogenous harmful substances in a complicated matrix.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉3-Methyl-1,2,3-butanetricarboxylic acid (MBTCA) is a secondary organic aerosol and can be used as a unique emission marker of biogenic emissions of monoterpenes. Seasonal variations and differences in vegetation cover around the world may lead to low atmospheric MBTCA concentrations, in many cases too low to be measured. Hence, an important tool to quantify the contribution of terrestrial vegetation to the loading of secondary organic aerosol may be compromised. To meet this challenge, a dispersive liquid–liquid microextraction (DLLME) method, known for the extraction of hydrophobic compounds, was extended to the extraction of polar organic compounds like MBTCA without compromising the efficiency of the method. The extraction solvent was fine-tuned using tri-〈em〉n〈/em〉-octyl phosphine oxide as additive. A multivariate experimental design was applied for deeper understanding of significant variables and interactions between them. The optimum extraction conditions included 1-octanol with 15% tri-〈em〉n〈/em〉-octyl phosphine oxide (w/w) as extraction solvent, methanol as dispersive solvent, 25% NaCl dissolved in 5 mL sample (w/w) acidified to pH 2 using HNO〈sub〉3〈/sub〉, and extraction time of 15 min. A limit of detection of 0.12 pg/m〈sup〉3〈/sup〉 in air was achieved. Furthermore, unique complexation behavior of MBTCA with iron(III) was found when analyzed with ultra-high-performance liquid chromatography coupled with electrospray ionization–quadrupole time-of-flight mass spectrometry (UHPLC–ESI–QToF). A comprehensive overview of this complexation behavior of MBTCA was examined with systematically designed experiments. This newly discovered behavior of MBTCA will be of interest for further research on organometallic photooxidation chemistry of atmospheric aerosols.〈/p〉 〈p〉 〈span〉 〈caption〉 〈strong〉Graphical abstract〈/strong〉 〈em〉 〈div〉 〈strong〉a〈/strong〉) Additive assisted DLLME and MBTCA complexes with Fe(III), 〈strong〉b〈/strong〉) A good quality figure is attached in ppt format to facilitate editable objects〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1741_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We describe the synthesis of new chiral calix[4]arene derivatives having (〈em〉R〈/em〉)-1-phenylethylamine, (〈em〉S〈/em〉)-1-phenylethylamine, (〈em〉R〈/em〉)-2-phenylglycinol, and (〈em〉S〈/em〉)-2-phenylglycinol moieties, and chiral recognition studies for enantiomers of some selected α-amino acid derivatives such as alanine, phenylalanine, serine, and tryptophan using a quartz crystal microbalance (QCM). Initial experiments indicated that the highest selective chiral recognition factor was 1.42 for alanine enantiomers. The sensitivity, limit of detection, and time constant for 〈span〉l〈/span〉-alanine were calculated as 0.028 Hz/μM, 60.9 μM, and 36.2 s, respectively. The results indicated that real-time, sensitive, selective, and effective chiral recognition of alanine enantiomers was achieved with a QCM sensor coated with a chiral calix[4]arene derivative having (〈em〉R〈/em〉)-2-phenylglycinol moieties.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1705_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The growing use of reclaimed water in agriculture worldwide calls for developing high-sensitivity methods to quantify wastewater-derived organic contaminants in soils so that the potential risk of this irrigation practice can be properly assessed. This work describes an analytical method for the determination of trace levels of 14 drugs that are known to be poorly removed during conventional wastewater treatment in soil. The analytes selected for investigation included ten pharmaceuticals from different therapeutic classes (carbamazepine, diclofenac, cis-diltiazem, lamotrigine, methadone, midazolam, oxcarbazepine, sulfamethoxazole, trimethoprim, valsartan), one illicit drug (cocaine), and three transformation products/metabolites (acridone, 4′-hydroxydiclofenac, and valsartan acid), thereby covering a broad range of physical–chemical properties. The methodology developed was based on ultrasonic solvent extraction (USE) of the analytes from the soil matrix, and subsequent clean-up and analysis of the USE extracts with a fully automated approach by means of solid-phase extraction and liquid chromatography-tandem mass spectrometry detection (online SPE-LC-MS/MS). The method was fully validated with affording method detection and quantification limits ranging from 0.03 to 1 ng g〈sup〉−1〈/sup〉 and from 0.09 to 3.3 ng g〈sup〉−1〈/sup〉, respectively. This method was applied to investigate the fate of the selected drugs in potting soil irrigated for a long term (60 days) either with water containing the target compounds at a concentration of 200 μg L〈sup〉−1〈/sup〉 or with wastewater treatment plant effluent and thus, at real environmental concentrations. All investigated compounds were found to accumulate in soil irrigated with artificially fortified water. The highest accumulation potential was observed for cis-diltiazem followed by methadone and midazolam that presented average concentrations of 1517 ng g〈sup〉−1〈/sup〉, 1041 ng g〈sup〉−1〈/sup〉, and 962 ng g〈sup〉−1〈/sup〉 d.w., respectively. On the contrary, oxcarbazepine (5.8 ng g〈sup〉−1〈/sup〉) and sulfamethoxazole (22 ng g〈sup〉−1〈/sup〉) were the target drugs presenting the lowest accumulation potential. Only trace levels of ten drugs were measured in soil irrigated with regenerated water (average concentrations between 1.6 and 4.7 ng g〈sup〉−1〈/sup〉 d.w.).〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1715_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A powerful technique to detect bone biomarkers has been developed for assessment of osteoporosis at the early stage. Two-dimensional multilayered gold-nanoparticle thin film (MTF-AuNPs) was demonstrated as a promising test platform for detection of bone biomarker, hydroxyproline (HYP), measured by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). With strong surface plasmon resonance and excellent homogeneity, facilely prepared, highly ordered, and large-scale MTF-AuNPs revealed high sensitivity of HYP in the SALDI-MS measurement without additional matrixes, such as α-cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB). Furthermore, the mass spectrum of HYP with MTF-AuNPs was significantly improved in signal intensity enhancement, background noise reduction, and signal-to-noise ratio amplification. The excellent reproducibility of HYP spectra with only 9.3% relative signal variation could be attributed to MTF-AuNPs’ high absorbance at a wavelength of 337 nm, low heat capacity, superior thermal conductivity, and outstanding homogeneity. The calibration curve showed high linear correlation between mass spectrum intensity and HYP concentration in the range of 1 to 100 μM, covering the whole level in healthy people and osteoporosis patients. In particular, the serum sample was directly deposited onto the MTF-AuNP sample substrate without any pretreatment and its HYP concentration was then successfully determined. We believe that the combination of SALDI-MS and MTF-AuNP sample substrates would be a potential approach for bone biomarker detection in the osteoporosis risk assessment.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1759_Figj_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉To develop bioconjugated materials, it is necessary to understand how the various elements present in a conjugate interact with one another. To gain insights into nanoparticle–capping agent–protein interactions, gold nanoparticles (AuNPs) measuring 30 nm in diameter were coated with different molecules bearing a thiol group: 3-mercaptopropionic acid, 6-mercaptohexanoic acid, and 11-mercaptoundecanoic acid. The covalent conjugation of AuNPs to the protein bovine serum albumin (BSA) via a cross-linker reaction with 〈em〉N〈/em〉-hydroxysuccinimide and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide was systematically investigated under different reaction conditions with variation of the concentrations of the mercaptoalkyl carboxylic acid (MA) and BSA. All the products were analyzed by UV–vis spectroscopy, gel electrophoresis, and Raman spectroscopy in every modification step. From analysis of the UV–vis results, it is possible at low concentrations of MA to see strong coupling among AuNPs, observed when they are aggregated by KCl, which does not happen at higher concentration of MA, indicating an AuNP-to-MA ratio of 1:130,000 is best for bioconjugation purposes. Agarose gel electrophoresis, a classic technique for biomolecule characterization, indicated that BSA is capable of altering the mobility of AuNPs when it modifies completely the surface of AuNPs because of its high molecular mass (around 66 kDa). Principal component analysis of surface-enhanced Raman spectroscopy data was successfully used as a chemometric tool to assist the characterization of the nanoparticle modification with linker molecules in the absence and presence of different BSA concentrations, making it possible to clearly evaluate the gradual substitution/modification of AuNPs (1:13,000 〈 1:65,000 〈 1:130,000 AuNP-to-MA ratio) and the conjugation with BSA, which is homogenous at a concentration of 0.01 g L〈sup〉-1〈/sup〉.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1758_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉G protein-coupled receptors (GPCRs), G proteins, and their signaling associates are major signal transducers that control the majority of cellular signaling and regulate key biological functions including immune, neurological, cardiovascular, and metabolic processes. These pathways are targeted by over one-third of drugs on the market; however, the current understanding of their function is limited and primarily derived from cell-destructive approaches providing an ensemble of static, multi-cell information about the status and composition of molecules. Spatiotemporal behavior of molecules involved is crucial to understanding in vivo cell behaviors both in health and disease, and the advent of genetically encoded fluorescence proteins and small fluorophore-based biosensors has facilitated the mapping of dynamic signaling in cells with subcellular acuity. Since we and others have developed optogenetic methods to regulate GPCR–G protein signaling in single cells and subcellular regions using dedicated wavelengths, the desire to develop and adopt optogenetically amenable assays to measure signaling has motivated us to take a broader look at the available optical tools and approaches compatible with measuring single-cell and subcellular GPCR–G protein signaling. Here we review such key optical approaches enabling the examination of GPCR, G protein, secondary messenger, and downstream molecules such as kinase and lipid signaling in living cells. The methods reviewed employ both fluorescence and bioluminescence detection. We not only further elaborate the underlying principles of these sensors but also discuss the experimental criteria and limitations to be considered during their use in single-cell and subcellular signal mapping.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We present a facile strategy for highly sensitive and selective determination of copper(II) ions and vitamin C (ascorbic acid, AA) using new amino-terminated nitrogen-doped carbon quantum dots (CQDs) synthesized from melamine as the carbon and nitrogen source by the hydrothermal method. The CQDs have superior optical features, including a pH-sensitive photoinduced electron transfer process. The CQDs form a complex with Cu〈sup〉2+〈/sup〉 ions, leading to the development of naked-eye, colorimetric, and fluorometric determination. AA reduces the Cu〈sup〉2+〈/sup〉 ions to Cu〈sup〉+〈/sup〉 ions, which cannot form the complex. Thus the absorbance and fluorescence of the CQDs are recovered by addition of AA because of dissociation of the complex into Cu〈sup〉+〈/sup〉 and CQD. The in situ generation of reactive oxygen species when AA is added to Cu–CQD complexes in the presence of dissolved oxygen leads to the sensitive determination of AA, proposed on CQDs for the first time. The in situ generation of reactive oxygen species was confirmed by a fluorescence method using a hydroxyl radical indicator (i.e., coumarin). This novel “turn-off/turn-on” sensing approach using amine-functionalized CQDs is potentially applicable to determining the concentration of Cu〈sup〉2+〈/sup〉 ions and AA in the areas of materials chemistry, nanobiomedicine, nanobiotechnology, and bioengineering because of its high sensitivity, high selectivity, low cost, simple naked-eye readout, and good linearity.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1710_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Modular plants using intensified continuous processes represent an appealing concept for the production of pharmaceuticals. It can improve quality, safety, sustainability, and profitability compared to batch processes; besides, it enables plug-and-produce reconfiguration for fast product changes. To facilitate this flexibility by real-time quality control, we developed a solution that can be adapted quickly to new processes and is based on a compact nuclear magnetic resonance (NMR) spectrometer. The NMR sensor is a benchtop device enhanced to the requirements of automated chemical production including robust evaluation of sensor data. Beyond monitoring the product quality, online NMR data was used in a new iterative optimization approach to maximize the plant profit and served as a reliable reference for the calibration of a near-infrared (NIR) spectrometer. The overall approach was demonstrated on a commercial-scale pilot plant using a metal-organic reaction with pharmaceutical relevance.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1752_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A peptide-graphene oxide nanosensor has been developed to detect tobacco etch virus (TEV) protease and bacteria infected with an engineered bacteriophage. In the detection strategy, a peptide (sequence: RKRFRENLYFQSCP) is tagged with fluorophores and graphene oxide (GO) is used to adsorb the peptides while quenching their fluorescence. In the presence of TEV protease, fluoropeptides are cleaved between glutamine (Q) and serine (S), resulting in the recovery of fluorescence signal. Based on the fluorescent intensity, the detection limit of TEV protease is 51 ng/μL. Additionally, we have utilized the sensing system to detect bacteria cells. Bacteriophages, which were engineered to carry TEV protease genes, were used to infect target bacteria (〈em〉Escherichia coli〈/em〉) resulting in the translation and release of the protease. This allowed the estimation of bacteria at the concentration of 10〈sup〉4〈/sup〉 CFU/mL. This strategy has the potential to be developed as a multiplex detection platform of multiple bacterial species.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1766_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Diabetic kidney disease is a serious complication of diabetes that can ultimately lead to end-stage renal disease. The pathogenesis of diabetic kidney disease is complex, and fundamental research is still required to provide a better understanding of the driving forces behind it. We report regional metabolic aberrations from an untargeted mass spectrometry imaging study of kidney tissue using an insulinopenic rat model of diabetes. Diabetes was induced by intravenous injection of streptozotocin, and kidneys were harvested 2 weeks thereafter. Imaging was performed using nanospray desorption electrospray ionization connected to a high-mass-resolving mass spectrometer. No histopathological changes were observed in the kidney sections; however, mass spectrometry imaging revealed a significant increase in several 18-carbon unsaturated non-esterified fatty acid species and monoacylglycerols. Notably, these 18-carbon acyl chains were also constituents of several increased diacylglycerol species. In addition, a number of short- and long-chain acylcarnitines were found to be accumulated while several amino acids were depleted. This study presents unique regional metabolic data indicating a dysregulated energy metabolism in renal mitochondria as an early response to streptozotocin-induced type I diabetes.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1721_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉The 〈em〉Jatropha curcas〈/em〉 plant (〈em〉Jatropha〈/em〉) has been proposed as a source of biodiesel fuel, as it yields crude glycerol as an abundant by-product. Its by-products could serve as a starting material in making glycerol for FDA-regulated products. 〈em〉Jatropha〈/em〉 is not regarded as a source of edible vegetable oil since it contains phorbol esters (PEs). PEs, even at very low exposure concentrations, demonstrate various toxicities in humans and animals, but may not be detected by routine impurity analyses. Here, we demonstrate the development of a rapid and simplified method for the detection and quantification of 〈em〉Jatropha〈/em〉-derived PE toxins using ambient ionization mass spectrometry. To do this, we successfully coupled a paper spray ambient ionization source with an ion trap portable mass spectrometer. The paper spray source was assembled using chromatography papers, and analyte ions were generated by applying a high voltage to a wetted paper triangle loaded with PE standards. For method development, we used commercially available PE standards on an ion trap portable mass spectrometer. Standard solutions were prepared using ethanol with PE concentrations ranging from 1.0 to 0.0001 mg mL〈sup〉−1〈/sup〉. Spike and recovery experiments were performed using USP grade and commercially available glycerol. To discern chemical differences between samples, we applied multivariate data analysis. Based on the results obtained, paper spray coupled with a portable mass spectrometric method can be successfully adopted for the analysis of toxic contaminants present in glycerol-based consumer products with LOD and LOQ of 0.175 μg mL〈sup〉−1〈/sup〉 and 0.3 μg mL〈sup〉−1〈/sup〉 respectively. This direct, simple design, and low-cost sampling and ionization method enables fast screening with high sensitivity in non-laboratory settings.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1717_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Dielectrophoresis (DEP) brings about the high-resolution separations of cells and other bioparticles arising from very subtle differences in their properties. However, an unanticipated limitation has arisen: difficulty in assignment of specific biological features which vary between two cell populations. This hampers the ability to interpret the significance of the variations. To realize the opportunities made possible by dielectrophoresis, the data and the diversity of structures found in cells and bioparticles must be linked. While the crossover frequency in DEP has been studied in-depth and exploited in applications using AC fields, less attention has been given when a DC field is present. Here, a new mathematical model of dielectrophoretic data is introduced which connects the physical properties of cells to specific elements of the data from potential- or time-varied DEP experiments. The slope of the data in either analysis is related to the electrokinetic mobility, while the potential at which capture initiates in potential-based analysis is related to both the electrokinetic and dielectrophoretic mobilities. These mobilities can be assigned to cellular properties for which values appear in the literature. Representative examples of high and low values of properties such as conductivity, zeta potential, and surface charge density for bacteria including 〈em〉Streptococcus mutans〈/em〉, 〈em〉Rhodococcus erythropolis〈/em〉, 〈em〉Pasteurella multocida〈/em〉, 〈em〉Escherichia coli〈/em〉, and 〈em〉Staphylococcus aureus〈/em〉 are considered. While the many properties of a cell collapse into one or two features of data, for a well-vetted system the model can indicate the extent of dissimilarity. The influence of individual properties on the features of dielectrophoretic data is summarized, allowing for further interpretation of data.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1757_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Chemical composition in fingermarks could provide useful information for forensic studies and applications. Here, we evaluate the feasibility of analysis and imaging of fingermarks via elements by synchrotron radiation X-ray fluorescence (SRXRF) and commercial X-ray fluorescence (XRF). As a proof of concept, we chose four brands of sunscreens to make fingermarks on different substrates, including plastic film, glass, paper, and silicon wafer. We obtained an evident image of fingermarks via zinc and titanium by XRF methods. In addition, the ratios of element concentrations in sunscreen fingermarks were obtained, which were in accordance with the results obtained by acid digestion and ICP-OES analysis. In comparison, commercial XRF offers the most advantages in terms of non-destructive detection, easy accessibility, fast element images, and broad applicability. The possibility to acquire fingermark images simultaneously with element information opens up new avenues for forensic science.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1718_Figa_HTML.jpg"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Plant development, growth, and adaptation to stress are regulated by phytohormones, which can influence physiology even at low concentrations. Phytohormones are chemically grouped according to both structure and function as auxins, cytokinins, abscisic acid, jasmonates, salicylates, gibberellins, and brassinosteroids, among others. This chemical diversity and requirement for highly sensitive detection in complex matrices create unique challenges for comprehensive phytohormone analysis. Here, we present a robust and efficient quantitative UPLC-MS/MS assay for 17 phytohormones, including jasmonates, salicylates, abscisic acid, gibberellins, cytokinins, and auxins. Using this assay, 12 phytohormones were detected and quantified in sorghum plant tissue without the need for solid phase extraction (SPE) or liquid-liquid extraction. Variation of phytohormone profiles was explored in both root and leaf tissues between three genotypes, harvested at two different developmental time points. The results highlight the importance of tissue type, sampling time, and genetic factors when designing experiments that involve phytohormone analysis of sorghum. This research lays the groundwork for future studies, which can combine phytohormone profiling with other datasets such as transcriptome, soil microbiome, genome, and metabolome data, to provide important functional information about adaptation to stress and other environmental variables.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1658_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Extra virgin olive oil provides an important intake of α-tocopherol, which is part of vitamin E complex. A fast analytical method for its quantification, based on paper spray mass spectrometry, has been developed. The methodology possesses the ability to record mass spectra without sample preparation or preseparation steps. The experiments were performed in Multiple Reaction Monitoring scan mode; in particular, the transitions 〈em〉m/z〈/em〉 429 → 〈em〉m/z〈/em〉 163 for α-tocopherol and 〈em〉m/z〈/em〉 435 → 〈em〉m/z〈/em〉 169 for the labeled internal standard were monitored, in order to obtain the greatest specificity and the best sensitivity. The accuracy of the method was tested analyzing spiked samples prepared at concentrations within the dynamic range of the calibration curve, which returned values near 100%. Furthermore, good values of LOQ and LOD were obtained, demonstrating that this approach can be applied for a rapid screening of tocopherols in different vegetable oils. The results were compared with analyses performed by traditional chromatographic methods.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1727_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉We introduce rapid replica molding of ordered, high-aspect-ratio, thiol-ene micropillar arrays for implementation of microfluidic immobilized enzyme reactors (IMERs). By exploiting the abundance of free surface thiols of off-stoichiometric thiol-ene compositions, we were able to functionalize the native thiol-ene micropillars with gold nanoparticles (GNPs) and these with proteolytic α-chymotrypsin (CHT) via thiol-gold interaction. The micropillar arrays were replicated via PDMS soft lithography, which facilitated thiol-ene curing without the photoinitiators, and thus straightforward bonding and good control over the surface chemistry (number of free surface thiols). The specificity of thiol-gold interaction was demonstrated over allyl-rich thiol-ene surfaces and the robustness of the CHT-IMERs at different flow rates and reaction temperatures using bradykinin hydrolysis as the model reaction. The product conversion rate was shown to increase as a function of decreasing flow rate (increasing residence time) and upon heating of the IMER to physiological temperature. Owing to the effective enzyme immobilization onto the micropillar array by GNPs, no further purification of the reaction solution was required prior to mass spectrometric detection of the bradykinin hydrolysis products and no clogging problems, commonly associated with conventional capillary packings, were observed. The activity of the IMER remained stable for at least 1.5 h (continuous use), suggesting that the developed protocol may provide a robust, new approach to implementation of IMER technology for proteomics research.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1674_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This study compares alternative approaches for analyzing phytocannabinoids in different plant materials. Three chromatographic analytical methods (ultra-high-performance liquid chromatography with tandem mass spectrometric detection and gas chromatography with mass spectrometric and flame ionization detection) were evaluated regarding selectivity, sensitivity, analytical accuracy, and precision. The performance of the methods was compared and all three methods were demonstrated to be appropriate tools for analyzing phytocannabinoids in cannabis. Gas chromatography coupled with mass spectrometric detection showed slightly better accuracy in determining phytocannabinoid acids, which are often difficult to quantify owing to their limited stability. Aspects of sample preparation, such as material homogenization and extraction, were also considered. A single ultrasonic-assisted ethanolic extraction of dried and powdered plant samples of cannabis was shown to be exhaustive for extracting the samples prior to analysis.〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉A novel fluoro-chromogenic rhodamine spirolactam probe (RP) has been prepared through the condensation of rhodamine hydrazine and 2-acetylpyridine, which displayed the detection of Cu〈sup〉2+〈/sup〉 with high selectivity over a large number of other common metal ions. It shows a “turn-on” response to paramagnetic Cu〈sup〉2+〈/sup〉 with an about 12-fold enhancement, and a color change from colorless to red that is observable by the naked eye. These changes are ascribed to the ring-opening of the spirolactam in RP, and subsequent host–guest coordination. The 2:1 binding stoichiometry of RP to Cu〈sup〉2+〈/sup〉 was confirmed by Job’s and B-H plots. The resulting fluorescence enhancement can be used to detect Cu〈sup〉2+〈/sup〉 at concentrations from 2.0 to 20.0 μM with a limit of detection of 0.21 μM, which was lower than the maximum allowable Cu〈sup〉2+〈/sup〉 level set by the WHO. Finally, RP has been utilized to monitor Cu〈sup〉2+〈/sup〉 in living cells and natural water.〈/p〉 〈p〉 〈span〉 〈caption〉 〈em〉 〈div〉Graphical abstract〈/div〉 〈/em〉 〈/caption〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1748_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉In this study, a simple colorimetric probe was developed for rapid and highly sensitive detection of malathion based on gold nanoparticles (AuNPs) anti-aggregation mechanism. A certain amount of NaOH can cause the aggregation of citrate-stabilized AuNPs due to the electrostatic interactions, and the color of AuNP solution changes from wine-red to gray. While in the presence of malathion, malathion is easily hydrolyzed in a strong alkali environment (pH 〉 9), followed by the production of a mass of negative charges, and thus the aggregated AuNPs turns to well-dispersed and the color of AuNP solution changes from gray to wine-red. This characteristic change can be visualized with the naked eye and quantitatively detected by an ultraviolet-visible (UV-Vis) spectrometer. Under optimized conditions, this probe exhibited a linear response to malathion in the concentration range of 0.05–0.8 μM with a limit of detection (LOD) down to 11.8 nM. The probe also showed good specificity for malathion detection in the presence of other interfering pesticide residues. Furthermore, the probe was successfully employed to detect malathion in environmental samples, with a recovery of 94–107% and a relative standard deviation (RSD) less than 8%. The results demonstrated that the proposed colorimetric probe based on anti-aggregation of AuNPs could be used for quantitative analysis of malathion and provided great potential for malathion determination in environmental samples.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1703_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉This paper proposed a newly developed heart-cutting two-dimensional supercritical fluid chromatography-high-performance liquid chromatography system coupled to tandem mass spectrometry (SFC-HPLC-MS/MS) for the determination of four tobacco-specific nitrosamines (TSNAs) in cigarette mainstream smoke. The orthogonality of five SFC columns and two HPLC columns was evaluated. The 1-AA column was applied for the first dimensional (1D) SFC separation to isolate the target compounds from the complex cigarette smoke matrices, and a trapping column in conjunction with an isocratic pump was employed to capture the 1D elutes. Then, the trapped 1D elutes were transferred into the C18 column through a two-position/six-port valve for the second dimensional (2D) analysis. The ion suppression was significantly reduced by the established SFC-HPLC system; meanwhile, the matrix interferences were eliminated as the results demonstrated. A dynamic range between 0.1 and 20 ng/mL was achieved with LOQs of 0.72 μg/cig for N-nitrosonornicotine (NNN), 0.66 μg/cig for nicotine-derived nitrosamine ketone (NNK), 0.81 μg/cig for N-nitrosoanatabine (NAT), and 0.39 μg/cig for N-nitrosoanabasine (NAB). All the results revealed that the presented method exhibited good repeatabilities and recoveries and could be used as a rapid and reliable approach for routine analysis of TSNAs in mainstream smoke.〈/p〉 〈p〉 〈span〉 〈span〉 〈img alt="" src="https://static-content.springer.com/image/MediaObjects/216_2019_1746_Figa_HTML.png"〉 〈/span〉 〈/span〉 〈/p〉

Description: 〈h3〉Abstract〈/h3〉 〈p〉Folates are typically present in polyglutamyl form in organisms. In traditional extraction methods, polyglutamyl folates are hydrolyzed to monoglutamates, sacrificing valuable information. To advance folate metabolism research, we developed an accurate, sensitive, and reproducible extraction method for polyglutamyl folate species in maize, the main crop in most parts of the world. Twelve folates, including six polyglutamyl folates, were simultaneously determined in maize for the first time using high-performance liquid chromatography-tandem mass spectrometry. The glutamation states of the folates were protected by boiling, which inactivated the native conjugases. α-Amylase and protease were added to obtain better recoveries and decrease difficulties in centrifugation and filtration. The recoveries (〈em〉n = 5〈/em〉) of six polyglutamyl folates were between 80.5 and 101%. All calibration curves showed good linear regression (〈em〉r〈/em〉〈sup〉2〈/sup〉 ≥ 0.994) within the working range. The instrumental limits of detection and quantitation ranged from 0.070 to 2.4 ng/mL and 0.22 to 8.0 ng/mL, respectively. Intra- and inter-day precision was below 7.81% and 11.9%, respectively (〈em〉n = 5〈/em〉). Using this method, changes in poly- and monoglutamyl folates during maize germination were determined for the first time. The results suggest that folates were largely synthesized as germination initiated, and 5-methyltetrahydrofolate was the most abundant species. Tetraglutamyl 5-methyltetrahydrofolate contributed more than 50% of the 5-methyltetrahydrofolate species. Inverse changes in contents of 5,10-methenyltetrahydrofolate, and 10-formyl folic acid, monoglutamate, and diglutamate of 5-formyltetrahydrofolate were also observed, indicating potential regulation. Additionally, polyglutamyl folates in sweet potatoes were determined using this method, indicating its applications in starchy crops.〈/p〉