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  • Column liquid chromatography  (495)
  • 42.75
  • Chemistry
  • GEOPHYSICS
  • Springer  (499)
  • 1990-1994  (499)
  • 1950-1954
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Keywords
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Years
Year
  • 101
    Electronic Resource
    Electronic Resource
    Determination of carbidopa and levodopa in human plasma by high-performance liquid chromatography with electrochemical detection (1993)
    Springer
    Chromatographia 35 (1993), S. 607-612 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbidopa and levodopa in plasma ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A validated reversed-phase high-performance liquid chromatographic procedure employing electrochemical detection (LCEC) for the analysis of carbidopa and levodopa in human plasma is reported. The method is sensitive and specific with amperometric detection at a glassy carbon working electrode with Eapp=0.75 V vs. Ag/AgCl. The retention times of levodopa, internal standard, and carbidopa are 3.3, 4.5, and 9.7 minutes, respectively, with an overall chromatographic run time of 12.0 minutes. The peak height ratio versus plasma concentration is linear over the range of 5.0 to 500 ng/mL for each analyte and exhibits correlation coefficients of 0.9957 or better (n=9). The mean absolute recovery of carbidopa and levodopa using the described assay is 36.6 and 66.0%, respectively. The inter- and intra-day accuracy and precision are within 11.8% of the actual values for all concentrations. Also, due to the demonstrated instability of carbidopa and levodopa in plasma a procedure is provided to circumvent this. Blood collected in pre-treated Vacutainer tubes can be stored in an ice bath for up to 4 hours without any significant degradation, thereby providing a practical means for processing several clinical samples simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267924
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  • 102
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    High-performance liquid chromatographic separation of fullerene mixtures using a novel stationary phase (1993)
    Springer
    Chromatographia 35 (1993), S. 631-636 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; FullereneSep® ; Separation factor ; HPLC-particle beam mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic separation of fullerene mixtures in the range C60 to C100 can be achieved using a novel stationary phase which rivals the performance of the more expensive ‘Pirkle-type’ columns currently employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267928
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  • 103
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    Spurious interferences in the ion chromatographic determination of trace elements in human hair (1993)
    Springer
    Chromatographia 35 (1993), S. 675-678 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Trace metal determination ; Sample contamination ; Human hair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dynamic ion-exchange chromatographic analysis of bivalent ions, such as Cu, Pb, Zn, Ni, Co and Mn in resistant organic matrices needs preliminary wet ashing with oxidizing acids (HNO3 and HClO4). Such treatment may lead to an increase in the amounts of metals present in the sample due to their release from containers or equipment used in an acidic environment and to metal impurities contained in the acids. The effect of these interferences in the determination of trace metals in human hair was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267936
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  • 104
    Electronic Resource
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    Individual determination of ortho and non-ortho substituted polychlorobiphenyls (PCBs) in sediments by high performance liquid chromatographic pre-separation and gas chromatography/ECD detection (1993)
    Springer
    Chromatographia 36 (1993), S. 65-70 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; GC/ECD detection ; PCBs, ortho and non-ortho ; Chromatographic separation ; Congener determination ; FTIR identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure for the individual determination of ortho and non-ortho PCB congeners in sediments, using high performance liquid chromatography (HPLC) preseparation and gas chromatography/ECD detection, is described. Gas chromatography/FTIR spectrometry (GC/FTIR) and gas chromatography/mass spectrometry (GC/MS) were employed for individual congener identification and determination. Sample extraction, clean-up of extract and selective elution procedures were optimized by using reference certified marine sediment samples. Recovery and precision were typically 83% and 16% respectively at 2 ng/g of total PCB content. The proposed procedure, tested by analyzing real sediment samples, showed a reproducibility better than 20% at 13 ng/g PCB level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263839
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  • 105
    Electronic Resource
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    HPLC determination of pyroglutamic acid as a degradation product in parenteral amino acid formulations (1993)
    Springer
    Chromatographia 36 (1993), S. 75-78 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Glutamine ; Pyroglutamic acid ; Amino acids formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects. Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur. The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 μm Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5. Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263841
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  • 106
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    Determination of picomole amounts of carbonyls as luminarin hydrazones by high-performance liquid chromatography with fluorescence detection (1993)
    Springer
    Chromatographia 36 (1993), S. 96-104 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbonyl compounds ; Luminarin hydrazides ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorogenic reagents (luminarin 3, luminarin 11 and luminarin 12), having a quinolizinocoumarin moiety as fluorophore and a carboxylic acid hydrazide function as reacting group, have been developed. These reagents were found to be highly sensitive fluorescence derivatization reagents for aldehydes and ketones in high-performance liquid chromatography. The reagents readily react with carbonyl compounds in aqueous sulphuric acid solution (0.1 M) at room temperature to produce the corresponding hydrazone derivatives, which can be separated on both reversed or normal-phase column. The structures of the derivatives were studied, together with their properties in reversed and normalphase chromatographic systems. UV absorbance, corrected fluorescence spectral data and quantum yields of luminarin 3, luminarin 11 and luminarin 12 are presented. The detection limits (signal to noise ratio=3) for aldehydes and ketones were in the sub-pmol range. Luminarin 3 was also applied to the determination of hydroxymethylfurfural (HMF) in orange juices and concentrates. The method for HMF involves the solid-liquid extraction of the juice by using a C-18 cartridge prior to derivatization and normal-phase separation of the derivative with fluorimetric detection at 387 nmex., 444 nm em. The calibration curve was linear for amounts of HMF ranging from 0.1 to 10 nmol. Intrarun relative standard deviation was 12.8% for 0.1 nmol and 2.6% for 1 nmol. Recovery studies indicated an average of 98.7±1.9% for juice concentrate and 99.8±3.2% for pasteurized juice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263844
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  • 107
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    Chemometric optimization in drug analysis by HPLC: A critical evaluation of the quality criteria used in the analysis of drug purity (1993)
    Springer
    Chromatographia 36 (1993), S. 120-124 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Method development ; Chemometrics ; Response criteria ; Analysis of drug purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimization procedures require adequate response criteria to assess the quality of each chromatogram obtained during the process. The objective of this paper is to evaluate the possibility of using different resolution functions, in the chromatographic separation of a drug and its impurities (particularly the impurity just eluted after the drug). This study shows the limits of some resolution expressions. The interest of the simple Δt criterion, the difference between retention times, is presented in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263847
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  • 108
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    Effect of the organic modifier on the retention of retinoids in reversed-phase liquid chromatography (1993)
    Springer
    Chromatographia 36 (1993), S. 147-151 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polarity ; Retinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of retinoids in reversed-phase liquid chromatography was studied using aqueous mobile phases of different composition (methanol 94–86% and acetonityrile 92–82%) at five temperatures (40–60 °C). With both organic modifiers the effect of the molecular structure increased as the water content and the polarity of the mobile phase increased. The temperature-dependence increased in the same manner with aqueous acetonitrile mobile phases. The π-π interactions between the retinoids and acetonitrile diminish when the water content of the mobile phase is increased, as happens also to the hydrophobic interactions with both organic modifiers. The net effect of these changes depends on the composition of the mobile phase. There was excellent correlation of retention with all polarity parameters studied(ϕ, P′, xe, xd, xn, E T N , δT, δ, δo and δd), when the calculations were made separately with methanol and acetonitrile. The volume fraction of the organic modifier, ϕ, was the only parameter describing the retention well in both organic modifiers simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263852
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  • 109
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    Determination of a new calcium antagonist in human plasma by liquid extraction enrichment and HPLC with UV detection (1993)
    Springer
    Chromatographia 36 (1993), S. 343-346 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aromatic amines ; Arylbenzylamide methylthioether derivative ; SL 85.1016 ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method has been developed for the determination of SL 85.1016, a new calcium antagonist arylbenzylamide methylthioether derivative. SL 85.1016 and the internal standard, SL 87.0210, are extracted from alkaline human plasma withn-hexane and back extracted into 0.05 M phosphate buffer (pH 2.5; 0.2 ml). Acetonitrile (50 μl) is added to the final aqueous extract in order to prevent absorption of the compounds of interest onto the walls of the glass tube; this solution then is partially processed by HPLC on a C18 column with UV detection (254 nm). The determination limit of the method is 2 ng.ml−1 of SL 85.1016 in human plasma; the response to the drug is linear in the range 2–200 ng.mg−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263888
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  • 110
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    Analysis ofAllium sulfur amino acids by HPLC after derivatization (1993)
    Springer
    Chromatographia 36 (1993), S. 347-350 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Allium ; Derivatization ; S-alk(en)yl-L-cysteine sulfoxides ; Sulfur amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two pre-column derivatization procedures coupled with reversed phase HPLC have been compared for the analysis ofS-Alk(en)yl0L-cysteine sulfoxides in variousAllium species. In order to establish external standards some (+/-) sulfoxides were synthesized, using a new method to enhance asymmetric synthesis of the diastereoisomers. The first derivatization method is the formation ofo-phthaldialdehyde/tert.-butylthiol derivatives which can be analyzed using UV detection. The second, presently used for amino acid analysis, is the Waters Pico-Tag method, which employs phenylisothiocyanate as derivatization reagent. As the Pico-Tag method was found to be the most efficient for determination ofS-alk(en)yl-L-cysteine sulfoxides it was used to determine the alliin content of various samples of garlic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263889
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  • 111
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    Collaborative study of the analysis of chlortetracycline by liquid chromatography on octylsilyl silica gel (1993)
    Springer
    Chromatographia 37 (1993), S. 640-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlortetracycline ; Reversed-phase silical gel ; C8 bonded phase ; Collaborative study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An established method for the analysis of chlortetracycline by liquid chromatography using octylsilylated silica gel as the stationary phase was examined in a multicentre study involving five laboratories and a total of six columns. Three chlortetracycline hydrochloride samples were analysed. The main component and the impurities were determined. An analysis of variance, treating each column as a different laboratory, showed an absence of consistent between-laboratory bias and the presence of a significant laboratory-sample interaction. The repeatability and the reproducibility of the method, expressed as relative standard deviations of the result of the determination of chlortetracycline hydrochloride, were calculated to be 0.9% and 1.1% respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274116
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  • 112
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    Characterization of octadecylsilica stationary phases by spectroscopic methods (1993)
    Springer
    Chromatographia 37 (1993), S. 627-634 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; ODS phases ; NMR and FTIR characterization ; Stationary phase functionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two spectroscopic methods, solid state NMR and diffuse reflectance FTIR, have been used in conjunction with liquid chromatographicretention data to identify and distinguish the functionality of octadecylsilica (ODS) stationary phases. NMR and FTIR spectra are indicative of various features of the different functionalities of the phases and this information can be used to elucidate the configuration of the organosilyl moiety in the ODS on the silica surface and explain why DSS phases have different molecular shape (mainly planarity) recognition capability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274114
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  • 113
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    Polypyrrole-coated silica as a new stationary phase for liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 423-428 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polymer-modified silica ; Polypyrrole cloride ; Polypyrrole dodecylsulfate ; Small molecules ; Polyaromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polypyrrole chloride and polypyrrole dodecylsulfate coated-silica packing materials have been synthesized. Reverse-phase chromtographuy was employed to characterise both packings. A series of test compounds with known properties was used as molecular probes. They included benzene and derivatives, basic drugs, and polyaromatic hydrocarbons. A commericial C18 column was also used for the purpose of comparison in some cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272259
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  • 114
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    Enantiomeric resolution ofN-alkyl-N-methylanilineN-oxides by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 487-491 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiralcel OD ; N-Alkyl-N-methylanilineN-oxide enantiomers ; Chiral nitrogen centre ; Flavin-containing monooxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method for the resolution of the enantiomers of a series ofN-alkyl-N-methylanilineN-oxides is reported. The resolutions were achieved using a Chiralcel, OD chiral stationary-phase with a mobile-phase of hexane and ethanol in varying proportions. The chromatographic order of elution of the enantiomers ofN-ethyl-N-methylanilineN-oxide was determined to be (+)-(R) before (−)-(S).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275784
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  • 115
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    Quantitative determination of sotolon in wines by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 539-542 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sotolon ; Vin jaune ; Flor-sherry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) is a key flavour compound in the french flor-sherry “Vin jaune”. This compound was determined quantitatively by extraction of 25 ml of wine on a XAD-4 resin, elution with diethyl ether, separation by HPLC on a Lichrospher 100 Diol column, elution with dichloromethane/hexane (60/40) and UV detection at 232 nm. The amount of sotolon in “Vin jaune” (120 to 268 μg/l) was related to the development of the yeast film over a period of 6 years. Only 6 to 51 μg/l were found in the “Vin de paille” which is made with overmaturated grapes of the same Savagnin vine-plant but without development of yeasts, and 80 to 140 μg/l in “Tokai” which are partly grown under a yeast film.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02275793
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  • 116
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    A micro-scale method employing surface plasmon resonance detection for the determination of conditions for immunoaffinity chromatography of proteins (1993)
    Springer
    Chromatographia 35 (1993), S. 45-49 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Immunoaffinity chromatography ; Proteins ; Surface plasmon resonance detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The BIAcoreTM Biosensor System utilizes a detection principle known as Surface Plasmon Resonance (SPR) which, in simple terms, detects changes in the refractive index of a solution in contact with a gold film. The gold film is surface modified with carboxymethylated dextran to produce a hydrophillic matrix onto which macromolecules may be covalently immobilized. In this respect, the BIAcoreTM is similar to any other insoluble matrix, such as a chromatographic support. The SPR detection principle, however, allows one to directly ‘visualize’ the interaction under study, in real time and without the need for reporter molecules such as enzyme-labels. In addition, the very small sample requirements, automated robotics unit and ease of data analysis suggest the potential use of the BIAcoreTM instrumentation for assay development and possibly process development, especially where bio-specific interactions such as immunoaffinity chromatography are used as a step in the process. In this report, we demonstrate the use of the BIAcoreTM SPR detector for the micro-scale determination of conditions for immunoaffinity chromatography of soluble complementreceptor 1, sCR1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278555
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  • 117
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    Optimisation of post-column reaction detector for HPLC of explosives (1993)
    Springer
    Chromatographia 35 (1993), S. 5-12 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column reaction detector ; Explosives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Improvements in selectivity and sensitivity in the analysis of common explosives, like nitrate esters, nitramines and nitroaromatic compounds can be achieved by post-column derivatisation in a two step reaction detector. The first step in derivatisation is the photolysis of the analytes with UV at 254 nm. The photo reactor consists of a crocheted 20 m Tefzel capillary, which is coiled around a low pressure mercury lamp. In second step the nitrite ion generated is subsequently detected by a colourimetric reaction. The azo dye formed can be selectively detected at 540 nm. Addition of alkali after chromatographic separation to prevent oxidation of initially formed nitrite to nitrate during photolysis leads to a complex multistage arrangement. However, the contribution to peak broadening by the reactor is negligible and it is possible to detect 25–50 ppb of nitramines and 30–100 ppb of nitrate esters. Another advantage of the method is the selective detection of nitro compounds, even in complex matrices. The trace analysis of explosives is of growing interest in forensic science as well as in environmental analysis. It has been shown [1] that explosives can easily be extracted from soil and debris by the use of supercritical carbon dioxide. The separation and determination of explosives by gas chromatography is hindered by their thermal instability. In HPLC only the nitro aromatic explosives can be detected with sufficient sensitivity. Other types of explosives like the esters of nitric acid or nitramines do not absorb sufficiently in the UV region for sensitive detection. It has been shown [2] that explosives are liable to photochemical decomposition in the UV region, resulting in nitrate and nitrite, which have been detected after separation by ion-pair chromatography with electrochemical detection. A more sensitive and selective detection of nitrite has been possible in flow injection analysis [3]. Here a modified Griess reaction has been used. In a first step nitrite ions are used to form the diazonium salt with sulfanilamide which is coupled in a second step with N-[naphthyl-(1)]-ethylene diamine (NED) to form a redviolet azo dye with an absorption maximum at 540 nm. The advantage of this method is selective detection in the visible region, where hardly any other organic components are detected, which might be present in a crude environmental sample. In this paper the transfer of the Griess reaction to post-column derivatisation in RP chromatography of explosives will be described, and the optimisation of trace analysis of these solutes will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278550
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  • 118
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    Optimizing separations in reversed-phase liquid chromatography by varying pH and solvent composition (1993)
    Springer
    Chromatographia 35 (1993), S. 18-32 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse phase ; Optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An interpretive optimization procedure in which pH can be one of the variables is presented with the emphasis on optimizing separations. When varying the pH in reversed-phase liquid chromatography the retention of ionogenic solutes will change. Thus, the selectivity between ionogenic and neutral solutes or between ionogenic solutes mutually can be optimized. However, pH also greatly affects the efficiency (plate count) and peak shape (asymmetry). Optimum selectivity (i.e. large differences in retention times) may be observed under conditions where peaks are broad and asymmetrical. Thus, it is essential to simultaneously consider retention, peak width and peak shape and their effects on separation (effective resolution) in pH-optimization studies. A procedure in which this is done is presented and applied to optimizing the separation of a synthetic mixture of selected pharmaceuticals. After initial experiments to establish the parameter space (boundaries for pH and binary methanol — water composition), twelve experiments are performed according to a 3×4 experimental design. At each loaction the retention, peak height, peak area and peak symmetry are recorded for each solute. These data are then used to build models for each of the four characteristics and for each solute. From this set of models the response surface, describing the quality of separation as a function of pH and composition, can be calculated. A variety of optimization criteria (quantifying quality of separation) can be used. The optimum corresponds to the highest point on the response surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278552
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  • 119
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    Separation and identification of fullerenes by liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 38-44 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; On-line and off-line identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fullerenes with a monomeric octadecylsilica bonded phase using n-hexane or toluene/methanol mobile phase systems is described. Analytical and preparative separations, incorporating on-line UV/VIS spectral measurements, confirmed the existence of large fullerenes such as C76, C78 and C84. However, isomers of C78 and C84 were not conclusively found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278554
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  • 120
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    HPLC determination of volatile phenols in wines (1993)
    Springer
    Chromatographia 35 (1993), S. 50-54 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Volatile phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An alternative to the traditional solvent extraction method used to extract and rapidly quantify ethyl-and vinylphenol and ethyl-and vinylgaiacol from wine is presented. The method is based on retention of volatile phenols on adsorbants. Among the tested resins, the most efficient, AG 2-X8 (anion exchange resin), worked as well with a synthetic solution as with wines. The percolation of clarified wine adjusted to pH 9 on this resin permits, in particular, the elimination of organic acids. Phenols are not eluted after rinsing the column with 1N HCl, but are eluted with methanol after this treatment. Good recovery (91 %) and good repeatability are observed. The eluate is directly analysed by HPLC on an RP18 column after two-fold dilution in water. The four volatile phenols were completely separated and detected by UV at 280 nm with high sensitivity (20–40 ppb). No interference with other compounds were noted in the different wines analysed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278556
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  • 121
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    Ion-pair LC of sugars at alkaline pH and pulsed electrochemical detection (1993)
    Springer
    Chromatographia 35 (1993), S. 61-66 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Ion-pair separation ; Pulsed electrochemical detection ; Hypercarb and PLRP-S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sugars, sugar acids, amino sugars and oligomers are separated as ion-pairs with hydrophobic counter ions at alkaline pH using PLRP-S and Hypercarb as solid phases. Important parameters for regulation of retention and selectivity are nature and concentration of the counter ion, pH (hydroxide concentration) and temperature. Reversals in the elution order wer obtained in some cases. Oligosaccharides are highly retained in these systems. The addition of organic modifiers to the mobile phase for elution of the solutes were found to interfere with the pulsed electrochemical detection (PED). Anions added to the mobile phase compete with the solutes for ion-pair retention, hence, decreasing the capacity factors, and phosphate could be used for this purpose in the separation of maltooligomers (M2-M10) from corn syrup.
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    URL: http://dx.doi.org/10.1007/BF02278558
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  • 122
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    Ion-pair LC of carbohydrates at alkaline pH. Separation and retention behaviour of glycoconjugates (1993)
    Springer
    Chromatographia 35 (1993), S. 55-60 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Ion-pair separation ; Glycoconjugates ; PRP-1 and PLRP-S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new technique for the separation of carbohydrates as ion-pairs in strongly alkaline solution is presented. Carbohydrates are weakly acidic and partly present as anions at pH≥12 [1]. They are retained as ion-pairs on polymeric solid phases (PRP-1 and PLRP-S) with a hydrophobic quaternary ammonium counter ion present in the mobile phase. The effects of nature and concentration of mobile phase components on the retention of carbohydrates have been investigated and an ion-pair distribution model is proposed. The influence of temperature indicated no changes in retention mechanism with high counter ion concentration, but the resolution decreased with increasing temperature. Saccharides added to the mobile phase were shown to increase the retention and the selectivity.
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    URL: http://dx.doi.org/10.1007/BF02278557
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    The glycan patterns at the individual glycosylation sites in orosomucoid from allergic reaction patients (1993)
    Springer
    Chromatographia 35 (1993), S. 90-92 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1-acid glycoprotein ; Complex glycans ; Allergic reaction ; Terfenadine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Little is known about the alterations that have occurred at the individual glycosylation sites in allergy patients or how these glycosylation patterns may change after anti-allergy treatments. Using reverse-phase HPLC, we have quantitated the glycoforms present at the individual glycosylation sites on orosomucoid isolated from the sera of allergic reaction patients and an allergic reaction patient treated with the antihistamine Terfenadine. The glycan structures isolated from the five glycosylation sites for the individual taking Terfenadine were all within normal ranges. It is suggested that if the changes in glycosylation in OMD in the allergic state are functionally driven, then it should be possible to correlate biological activities with quantitative changes at the individual glycosylation sites, and hence further define the role of OMD in allergy and inflammation.
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    URL: http://dx.doi.org/10.1007/BF02278562
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    A comparison of temperature and mobile phase composition effects for bonded liquid crystal and polymeric stationary phases in HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 85-89 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bonded liquid crystals ; Polymeric stationary phases ; Variable temperature studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using two polycyclyic aromatic hydrocarbons as solutes, a comparison is made between a bonded liquid crystal stationary phase and a conventional polymeric C-18 phase. The bonded nematic liquid crystal phase was the silanized form of 4-[4-(allyloxy)benzoyl-oxy]biphenyl and the polymeric phase was Vydac 201TP. Both phases display shape and planarity selectivity as indicated by the results of the variable temperature and mobile phase composition studies. The slot theory of retention can be used to explain these results. However, the liquid crystal phase is more sensitive to molecular geometry, probably due to its more ordered structure on the surface. Variable temperature experiments which compare retention during both heating and cooling provides additional support for this conclusion. With the polymeric bonded C-18 phase, each solute had identical retention at the same temperature during both the heating and cooling cycles. On the bonded liquid crystal phase, measurable differences in retention were observed at identical temperatures depending on whether the column was heated or cooled. This effect is attributed to a degree of partially reversible disordering which occurs as the column temperature was increased. However, conditioning with the appropriate mobile phase can restore the original retention characteristics of the bonded liquid crystal phase.
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    URL: http://dx.doi.org/10.1007/BF02278561
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    Chromatographic comparison of the relative Lewis acidities of alumina and zirconia (1993)
    Springer
    Chromatographia 35 (1993), S. 133-138 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand exchange chromatography ; Zirconium oxide ; Aluminum oxide ; Lewis acids and bases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic properties of alumina and zirconia are compared with respect to their relative Lewis acidities when parabenzoic acid derivatives are chromatographed in aqueous media. Weak Bronsted acids show similar capacity factors on alumina and zirconia. As solute Bronsted acidity increases, the capacity factor increases more significantly on the zirconia phase than on the alumina phase. Efficiencies, as determined by the dominant desorption rate constants, are generally comparable between the two phases with alumina showing slightly higher efficiencies, Secondary interactions between the solutes and the stationary phases are nearly absent on zirconia but are very apparent on the alumina phase.
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    URL: http://dx.doi.org/10.1007/BF02269691
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    Development and comparison of different fluorimetric HPLC-methods with standard methods for the determination of formaldehyde in the atmosphere (1993)
    Springer
    Chromatographia 35 (1993), S. 142-148 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Formaldehyde in air ; Fluorimetric detection ; Comparison of fluorescent derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three different fluorimetric methods for the measurement of atmospheric formaldehyde are described. The relatively unknown 2-diphenylacetylindan-1,3-dionhydrazine (DAIH) method was developed and optimized with an improved limit of detection of 2 ppbv corresponding to a sample volume of 7.5 L. Separation of lutidines necessary for the Nash method was successfully carried out and the separation time was reduced by a factor of 5. The detection limit of the Nash method was improved to 1 ppbv. In comparison, the N,N-diphenyl-1-naphthylamine-5-sulfonhydrazine (DNSH) method performed in a similar manner, reached an LOD of 0.5 ppbv. Finally, measurements made in candle smoke using the three different fluorimetric methods and three standard methods yielded very similar results.
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    URL: http://dx.doi.org/10.1007/BF02269693
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    HPLC determination of 18 β-glycyrrhetinic and glycyrrhizinic acids in toothpastes after solid phase extraction (1993)
    Springer
    Chromatographia 35 (1993), S. 167-172 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 18 β-glycyrrhetinic acid ; Glycyrrhizinic acid ; Toothpastes ; Solid phase extraction (SPE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC methods suitable for the selective and sensitive determination of 18 β-Glycyrrhetinic acid (GT) and Glycyrrhizinic acid (GZ) in toothpastes have been developed. The methods involve a preliminary quantitative solid phase extraction (C-18 sorbent) for sample clean-up and analyte concentration. Chromatographic separations were performed on reversed phase (C-8; C-18) columns using mixtures of methanol and phosphate buffers (pH 3.0) as the mobile phase under isocratic or gradient elution conditions. The method were applied successfully to the analysis of commercial toothpastes containing low levels (0.013–0.065%) of GT and GZ.
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    Direct enantiomeric analysis of amphetamine in plasma by simultaneous solid phase extraction and chiral derivatization (1993)
    Springer
    Chromatographia 35 (1993), S. 153-159 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amphetamine in plasma ; Enantiomeric separation ; Solid phase derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical approach has been developed for the one step determination of enantiomeric amphetamine composition in plasma, using on-line, pre-column solid phase derivatization with reversed phase HPLC separation. The high molecular weight protein components were excluded by the small pore structure of the polymer and washed out of the reaction column before derivatization. Spiked amphetamine in human plasma was extracted and derivatized by the polystyrene based FMOC-L-prolyl solid phase reagent. The derivatized diastereomers were separated on a conventional ODS column with an ACN/H2O mobile phase. No kinetic resolution or racemization was observed in this solid phase derivatization. Calibration plots and reproducibility experiments were performed to demonstrate the validity of the new approach. Automation of the procedure provided a simple and reproducible method for direct chiral recognition in plasma samples.
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    URL: http://dx.doi.org/10.1007/BF02269695
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    Determination of trace amounts of morpholine and its thermal degradation products in boiler water by HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 173-176 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-column derivatisation ; Morpholine and degradation products ; Boiler feed water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 μg ml−1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.
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    An improved HPLC system for the analysis of photosynthetic pigments (1993)
    Springer
    Chromatographia 35 (1993), S. 189-192 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoid pigments ; Chlorophylls ; Photosynthestic tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatography system for the analysis of photosynthetic pigments is presented. The method employs an octadecylsilica stationary phase, a programmed quaternary mobile phase consisting of mixtures of methanol, acetonitrile, water and hexane, and a photodiode array detector. Carotenoids and chlorophylls are rapidly analysed in a single chromatographic separation. Thecis-trans isomers of most carotenoids are separated by this method.
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    URL: http://dx.doi.org/10.1007/BF02269701
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    Determination of monensins A and B in the fermentation broth ofStreptomyces cinnamonensis by high performance liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 206-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Monensins A and B ; Fermentation broth ; Streptomyces cinnamonensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High performance liquid chromatography on an octadecyl silica column has been used to determine both the monensin A: monensin B ratio and by the method of standard addition, the concentration of both in the fermentation broth ofStreptomyces cinnamonensis. Refractive index detection was preferred to ultraviolet owing to the presence of UV-absorbing components which could not be completely separated from the substances of interest. A linear relationship was obtained from the calibration data. The coefficients of variation for the estimation both of the ratio and the concentrations of the compounds were better then 5%. The estimated limit of detection for both substances was about 1 μg/ml. The results obtained from the determination of the ratios of monensins were compared with those obtained by chemical ionization mass spectrometry. Chromatographic separation of monensins on the silica gel column is also described.
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    HPLC determination of antioxidant synergists and ascorbic acid in some fatty pharmaceuticals, cosmetics and food (1993)
    Springer
    Chromatographia 35 (1993), S. 232-236 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ascorbic acid ; Antioxidant synergists ; Food, pharmaceuticals and cosmetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A specific and sensitive reverse-phase HPLC method for the quantitative determination of ascorbic acid and antioxidant synergists (1-tartaric acid, citric acid, lactic acid as lithium lactate and EDTA) in fatty pharmaceuticals, cosmetics and food has been developed. Two extraction procedures were used; treatment with hot water, and extraction with water from a hexane dilution of the product. No significant differences between the two procedures were found (p〈0.05), except for ascorbic acid. Quantitative determinations were performed using a C-18 column and sulfuric acid (pH 1.95) mobile phase. With detection, at 210 nm, lactic acid overlapped with ascorbic acid, but the former could be readily identified by TLC. Ascorbic acid was detected at 254 nm, when lactic acid (as lithium lactate) did not interfere in the analysis. Mean recoveries for tartaric, citric and lactic acids were in the range 96–101%.
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    A study of the use of microdialysis probes as a sampling unit in on-line bioprocess monitoring in conjunction with column liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 285-289 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microdialysis ; Fermentation monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automated on-line sampling and analytical set-up for the control of fermentations was studied incorporating a microdialysis probe as the sampling device. Applications to a penicillin broth and an ethanol fermentation were studied. Typical recovery values of carbohydrates were found to be close to 100% even after exposure of the microdialysis probe in the process for about 30 h.
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    URL: http://dx.doi.org/10.1007/BF02277511
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    The on-line determination of the enantiomeric purity of enzymatically produced chiral compounds (1993)
    Springer
    Chromatographia 35 (1993), S. 264-268 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomer separation ; Stereospecific synthesis ; Crown ether phase ; Immobilized enzyme reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A prototype of a coupled-column chromatographic system has been developed to determine the enantiomeric purity of enzymatically produced chiral compounds. In this system, an immobilized enzyme HPLC reactor based upon α-chymotrypsin (ACHT-IMER) was linked through a switching valve to a chromatographic column containing a crown ether-based chiral stationary phase (CR-CSP). Although ACHT is normally stereospecific for the L-enantiomorphs of aromatic amino acids, L-tryptophan (L-TRP), L-tyrosine and L-phenylalanine, we were able to achieve the hydrolysis of D-TRP methyl and ethyl esters on the ACHT-IMER. The percent of hydrolysis of the D-TRP esters could be manipulated by varying the resident time in the ACHT-IMER. In a series of experiments, D,L-TRP methyl or ethyl esters were injected into the ACHT-IMER, the flow stopped and after resuming the flow, the eluent which contained the hydrolyzed aminoacids, D- and L-TRP, was switched onto the CR-CSP where the enantiomeric composition of the TRP peak was determined. This configuration is a model for other IMER/CSP coupled-column systems which can be used for analytical and preparative applications.
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    Determination of the lipophilicity of some anti-hypoxia drugs: Comparison of TLC and HPLC methods (1993)
    Springer
    Chromatographia 35 (1993), S. 275-280 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Anti-hypoxia drugs ; Lipophilic character and retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The lipophilicity of 14 anti-hypoxia drugs has been determined by reversed phase thin-layer (RPTLC) and reversed phase high performance liquid chromatography (RPHPLC) in eluent systems containing different concentrations of acetonitrile and potassium dihydrogen phosphate. There was significant correlation between lipophilicity and the specific hydrophobic surface area of the drugs in RPTLC, indicating that the drugs behave as an homologous series of compounds. In RPTLC the concentration of buffer has a negligible effect on the retention of the drugs whereas in RPHPLC the buffer concentration influenced the retention. This discrepancy can be explained by the lower sensitivity of RPTLC. There was strong correlation between lipophilicity values determined by both methods, proving that both are suitable for the determination of molecular lipophilicity.
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    Enantiomeric separation of close analogs to naturally occurring 1,4-benzoxazin-3-ones by liquid chromatography using β-cyclodextrin-modified stationary phase (1993)
    Springer
    Chromatographia 35 (1993), S. 302-304 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1,4-Benzoxazin-3-ones ; Cyclic hydroxamic acids ; β-Cyclodextrin modified silica gel ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic procedure on a 5 μm LiChroCART column using chemically bonded β-cyclodextrin (ChiraDex) as chiral selector was developed for the enantiomeric separation of four 2H-1,4-benzoxazin-3(4H)-ones which are close analogs of the cyclic hydroxamic acids 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3 (4H)-one (DIMBOA) naturally occurring inGramineae species.
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    A particle size distribution analysis of used HPLC column packing material (1993)
    Springer
    Chromatographia 35 (1993), S. 295-301 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Used column packings ; Particle size distribution ; Scanning electron microscopy ; Column age
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular progressions between the two extremes through the column. A new ODS-3 column showed log-normal size distributions from the inlet to the outlet ends. Spherical silica based column particle size distributions showed distinct shoulders on large central distribution peaks in most column sections with various degrees of shoulder erosion. The spherical resin based column showed a broader inlet particle size distribution progressing to a very narrow outlet distribution. SEMs of both irregular and spherical silica based columns revealed a larger number of undersized particles and debris at the outlet than inlet ends which could have resulted from stationary phase degradation, since this was not seen in the new ODS-3 column. While several SEMs of the spherical silica based columns revealed hollow spheres and twins, the spherical resin based column packing showed stress fractures or wrinkle lines resulting from use or dehydration.
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    Simultaneous isolation and determination of esculin and rutin in natural materials using SPE and HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 311-316 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isolation of natural products ; Solid phase extraction ; Chemically bonded phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Esculin (ESC) and rutin (RUT) have been simultaneously isolated from pharmaceutical natural materials by solid phase extraction (SPE). Determination of both substances was performed by reversed phase high performance liquid chromatography (RPHPLC) with UV detection. Optimization of the separation conditions showed that simultaneous isolation and determination of rutin and esculin from pharmaceutical material was possible. The recovery obtained was not lower than 95±2%.
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    Direct enantiomeric separation of racemic precursors to diltiazem hydrochloride and clentiazem maleate by HPLC on a chiral ovomucoid column (1993)
    Springer
    Chromatographia 35 (1993), S. 305-310 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomer separation ; Chiral ovomucoid column ; Diltiazem hydrochloride ; Clentiazem maleate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A direct HPLC separation method was developed for the determination of the enantiomers of racemic precursors to diltiazem (I) and its 8-chloro derivatives (II). The enantiomers were successfully separated on a chiral ovomucoid column using an aqueous-organic mobile phase (reversed-phase HPLC). The influence of the organic modifier and buffer pH on the retention and enantioselectivity was investigated. The chromatographic conditions chosen for the separation permitted complete resolution of the enantiomers of both the acid (Ib and IIb) and methyl ester precursors (Ia and IIa) within 20 min. The influence of sample load on retention times, theoretical plates numbers, peak heights and peak areas was also investigated. The peak areas showed a good linearity over the concentration range examined, although all the others were influenced significantly by the sample size. An optical antipode of the intermediate to be determined could be detected by the area-percentage method down to ca. 0.1%, together with the determination of its precursor, including its optical purity.
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    Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction techniques for sample clean-up (1993)
    Springer
    Chromatographia 35 (1993), S. 317-320 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Probenecid in urine ; Solid-phase extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 μg/ml concentration range; the limit of detection was 5 ng/mL.
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    Effects of organic modifier and ion-pair reagent in liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 390-394 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrostatic model ; Ion-pair reagent ; Organic modifier ; Prediction of k′ values
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The capacity factors of phenylamine and naphthylamine sulphonic acids in reversed-phase, ion-pair liquid chromatography (RP-IPC) were measured. The combined effects of organic modifier (Cb) and ion-pair reagent concentration (Cp) on retention follow an equation based on the electrostatic model: $$\ln k' = a + b lnC_p + cC_b $$ the experimental value of b correlates well with the value of 0.5 z (z=charge on analyte ion) predicted for mono and divalent ions. The measured value of b is, however, lower than that predicted for trivalent ions, which may be due to the effective number of charges being less than the apparent number. The absolute values of a and c are much larger than those in RP-HPLC in the absence of an ion-pair reagent, quantitative correlation of a and c with retention values in RP-HPLC and solute charges has been observed and a good linear relationship between a and c has been obtained, strongly supporting the validity of the electrostatic retention model. A critical value, R, at which the negative effect of methanol on retention is equal to the positive effect of the ion-pair reagent (TBAI) has been proposed. The critical values obtained are related to the behaviour of the solute, the ion-pair reagent and the stationary and mobile phases, and lies between −0.04 and −0.065 in most cases, which means that the increase by exp times (=2.718×) the ion-pair concentration the original is equivalent to a decrease of 0.04–0.065 in volume fraction of methanol
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    Simultaneous determination of two serine proteinases by hydrophobic interaction chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 381-386 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bovine trypsin ; Porcine kallikrein ; Bovine pancreatic trypsin inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The possibility of determining more than one enzyme at the same time has been examined. A new approach, based on the measurement of a direct and specific chromatographic signal obtained by hydrophobic interaction chromatography (HIC) of the stable complex formed with the inhibitor aprotinin, is proposed. A basic procedure for the quantitative determination of trypsin and kallikrein, taken as models, is described. The method is precise with a mean coefficient of variation of 3.1% and 3.5% for trypsin and kallikrein, respectively; the limit of determination for both enzymes is 0.17 nmol ml−1 in the original sample.
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    Influence of buffer composition on protein adsorption on agarose (Sepharose 6B) (1993)
    Springer
    Chromatographia 35 (1993), S. 387-389 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Buffer composition effect ; Agarose ; Albumin ; Ionic adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The adsorption of albumin on a commercial, high quality agarose (Sepharose® 6B) was studied in different buffers of low pH (4.00) and low molarity (9–11 mM). Eluents containing 0.025% albumin were introduced onto small gel columns until saturation and the adsorption capacity of the gel in different buffers calculated. Adsorption was high in solutions of monobasic acids. Although cation-exchange interactions between the protein and the gel matrix were found to be influenced essentially by the sodium ion concentration or ionic strength of the buffer, adsorption in cirate buffers is weak compared to that in formate, acetate or propionate buffers of about the same ionic strength (I=0.01).
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    Liquid chromatographic studies for essential fatty acids on a commercial alkyl phenyl bonded silica column (1993)
    Springer
    Chromatographia 35 (1993), S. 399-402 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyunsaturated fatty acids ; Direct injection ; Enthalpy of adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention studies on arachidonic acid 5, 8, 11, 14 all cis eicosatetraenoic acid, C20:4ω6), eicosapentaenoic acid (5, 8, 11, 14, 17 all cis eicosapentaenoic acid, C20∶5ω3) and docosahexaenoic acid (4, 7, 10, 13, 16, 19 all cis docosahexaenoic acid C22∶6ω3) were performed on a commercial μBondapak free fatty acid analysis column. The ternary mobile phase consisting of acetonitrile, water and tetrahydrofuran was used in an isocratic mode with differential refractometry detection. Retention data were mesured at various flow rates with two different, mobile-phase compositions. Capacity factors and enthalpy of adsorption were calculated from the retention data. Finally the retention mechanism is explained.
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    A model for polybutadiene coatings on porous silica (1993)
    Springer
    Chromatographia 35 (1993), S. 403-409 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phase packings ; Polybutadiene coating ; Polymer coatings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Non-wetting viscous liquids such as oligobutadiene prefer “active” sites such as pores during the process of physisorption. Thus, polybutadiene (PBD) coatings on porous silica do not result in a homogeneous polymer film but in an inhomogeneous loading where the bulk polymer is mainly sited in the pores of the silica. An increasing polymer loading leads to increasingly filled pores instead of a thicker polymer film. We cannot exclude the possibility that most of the surface is covered at least with a thin polymer film since the chromatographic behaviour is relatively good for polypeptides, which are highly susceptible to the silanol groups of silica.
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    URL: http://dx.doi.org/10.1007/BF02278594
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    Highly sensitive method for the determination of a new anthracycline: Pirarubicin (1993)
    Springer
    Chromatographia 35 (1993), S. 435-438 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pirarubicin and metabolites ; Anthracyclines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 μm, with a mobile phase of acetonitrile/methanol/formate-buffer.
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    URL: http://dx.doi.org/10.1007/BF02278598
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    The mechanism of separation of polythiolpeptides and metallopolythiolpeptides by covalent affinity chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 439-447 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Affinity chromatography ; Polythiolpeptides and metallopolythiolpeptides ; Mechanism of separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Covalent affinity chromatography with thiol-disulphide interchange (CAD-TDI) is a method for the separation of thiolproteins based on the interaction between disulphide bridges immobilised on a insoluble support and thiol groups in the protein undergoing separation. Mercury-thionein, cadmium-thionein and apothionein have been used as low molcular weight thiolproteins rich in cysteine residue. The proposed separation mechanism is more complex than those in the literature and can have anionic, cationic or a free radical character depending on the protein, the ligand and the conditions during separation.
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    URL: http://dx.doi.org/10.1007/BF02278599
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    Determination of phenolic antioxidants in pharmaceutical formulations by liquid chromatography and migration study on HDPE packagings (1993)
    Springer
    Chromatographia 35 (1993), S. 455-458 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV and electrochemical detectors ; Phenolic antioxidants ; Migration studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The performance of UV diode-array, spectrometric and electrochemical detectors was compared in the chromatographic analysis of trace amounts of six phenolic antioxidants. Quantitative validation was undertaken; the linearity range was wider using UV detection although the limits of detection were lower with electrochemical detection. UV detection was applied both to identification of an antioxidant in a hydrophilic suspension and to a migration study.
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    URL: http://dx.doi.org/10.1007/BF02278602
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    Quantitative structure chromatography relationships in reversed-phase high performance liquid chromatography: Prediction of retention behaviour using theoretically derived molecular properties (1993)
    Springer
    Chromatographia 37 (1993), S. 241-249 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pattern recognition ; Principal components ; Multiple linear regressions ; M.O. properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of theoretically calculated molecular properties as predictors for retention in reversed-phase HPLC has been explored. HPLC retention times have been measured for a series of 47 substituted aromatic molecules in three solvent mixtures and steric and electronic properties of these compounds have been derived using semi-empirical molecular orbital and empirical theoretical methods. A subset of the experimental data (a training set) was used to derive property-retention time relationships and the remaining data were then used to test the predictive capability of the methods. Good retention time prediction was possible using derived regression equations for individual solvents and after including solvent parameters it was possible to predict retention for all solvents using a single equation. This method showed that the most useful properties were calculated log P and the calculated dipole moment of the solutes, and the calculated solvent polarisability. In addition, 90% of the data were used to train an artificial neural network and the remaining 10% of the data used to test the network; excellent prediction was obtained, the neural network approach being as successful as the regression analysis.
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    URL: http://dx.doi.org/10.1007/BF02278628
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    Composition of 2-(3,5-dibromo-2-pyridylazo) diethylaminophenol chelates by liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 284-286 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Composition of chelates ; 3,5-diBr-PADAP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The composition of 3,5-diBr-PADAP metal chelates was determined by liquid chromatography employing appropriate eluents and non-polar bonded stationary phase. The metal-to-ligand ratios were 1∶2, 1∶2 and 1∶2 for Cu(II), Co(III) and Cr(III) respectively, and the V(V)-to-ligand ratio found to be 1∶1∶1 in V(V)-3,5-diBr-PADAP-H2O2 in the presence of H2O2. The results are in agreement with literature data.
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    URL: http://dx.doi.org/10.1007/BF02278635
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    HPLC determination of chlorine in air and water samples following precolumn derivatization to 4-bromoacetanilide (1993)
    Springer
    Chromatographia 37 (1993), S. 492-496 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorine in air and water ; Precolumn derivation ; 4-Bromoacetanilide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chlorine has been be determined in air and water samples by a rapid and sensitive method entailing precolumn derivatization to 4-bromoacetanilide. A mixed potassium bromide-acetanilide reagent was used as a trapping agent for chlorine in air, and for its derivatization. The 4-bromoacetanilide formed was determined by reversed-phase HPLC on an ODS column, using methanol-water, 65∶35 (v/v) as mobile phase; detection was at 240 nm. A rectilinear calibration graph was obtained for the range 0.1–30 μg mL−1 chlorine; the limit of detection found to be 0.01 μg mL−1. The precolumn derivative has been found to have a shelf-life of at least 21 days; this enables the use of the method for samples transported from the field to the analytical laboratory, or the testing of a variety of conditions for chlorine scrubbing studies without the need for immediate analysis of samples. Humic substances do not cause any interference with the proposed method and the presence of nitrite does not lead to artificially high results and consequent misleading conclusions of the presence of high levels of chlorine.
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    URL: http://dx.doi.org/10.1007/BF02275785
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    Polymers immobilized on silica gels as stationary phases for liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 549-561 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phases ; Polymer-coated silica ; Polymer-filled silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A variety of stationary phases for HPLC can be prepared by immobilization of organic polymers on silica gels. Such silica-polymer adsorbents combine the strength of an inorganic matrix with the selectivity and chemical inertness of organic resins. Moreover, effective shielding of residual silanols and the increase of column packing stability can also be achieved by modification of silica gels with organic polymers. There are two main approaches to the preparation of such composite sorbents. The first includes various routes for coating the silica surface with a polymer layer and the second is by filling the silica pores with a polymer network. A survey of polymers immobilized on silica gels and of various experimental procedures which can be used for composite sorbent synthesis is given in this review.
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    URL: http://dx.doi.org/10.1007/BF02275796
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    Liquid chromatographic separation of monoamino analogues of dideoxyadenosine and 9-(dideoxy-β-D-lyxo-pentofuranosyl)adenine from adenine (1993)
    Springer
    Chromatographia 35 (1993), S. 451-454 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenine ; Monoamino analogues of dideoxyadenosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic method that can separate each of the monoamino analogues of dideoxyadenosine and 9-(-dideoxy-β-D-lyxo-pentofuranosyl)adenine from their main degradation product, adenine, is described. The influence of the pH of the mobile phase, the type and concentration of the organic modifier and the concentration of the silanol masking agent and the buffer have been investigated. Several reversed phases were examined. Samples were finally analyzed on a 10 μm Spherisorb ODS1 column (250 mm×4.6 mm I.D.) using acetonitrile −0.2 M potassium phosphate buffer pH 6.0–0.2 M tetramethylammonium phosphate pH 6.0-water (5∶5∶0.5∶89.5, v/v) as the mobile phase. The interactions between the solute and the stationary phase are discussed in view of the basic properties of the compounds under study.
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    URL: http://dx.doi.org/10.1007/BF02278601
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    Rutin purity determination by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 506-508 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Rutin (3-rhamnoglucoside of quercetin) analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic method has been developed for the analysis of rutin. The method has high specifity and precision and is suitable for routine use. Detection is by measuring UV absorbance at 280 nm. The separation is carried out on a C-8 column with tetrahydrofuran in phosphate buffer gradient elution. The starting concentration of organic modifier, and the gradient are critical. The buffer used is a 0.1 M solution of NaH2PO4, adjusted to pH 3.0 with H3PO4. The lower quantitation limit is 0.5 μg/ml and as little as 0.05% of impurities (calculated as rutin) can be shown to be present.
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    URL: http://dx.doi.org/10.1007/BF02267908
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    Determination of doxycycline in small serum samples by liquid chromatography. Application to pharmacokinetical studies on small laboratory animals (1993)
    Springer
    Chromatographia 35 (1993), S. 524-526 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Doxycycline in serum ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several methods have been described for the analysis of doxycycline in serum which require at least 0.5 mL sample. The assay presented here requires small amounts of serum (0.1 mL) and shows good sensitivity. A Ultrabase C-18 column and mobile phase consisting of acetonitrile-bidistilled water (28∶72) were used, flow rate 1 mL min−1 and monitored at 350 nm. Linearity proved satisfactory between 0.025 and 2.5 μg mL−1 of serum. This assay for doxycycline showed good precision (coefficient of variation 〈6%) and allowed quantitation of serum levels as low as 25 ng mL−1 using 100 μL samples.
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    URL: http://dx.doi.org/10.1007/BF02267911
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    Optical resolution mechanisms of uniconazole and structurally related compounds on cyclodextrin-bonded columns (1993)
    Springer
    Chromatographia 35 (1993), S. 555-559 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cyclodextrin-bonded phase ; Optical resolution ; Uniconazole inclusion complex ; Nuclear magnetic resonance spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enantiomers of uniconazole have been separated by high-performance liquid chromatography on a γ-cyclodextrin-bonded column and the mechanisms of the chiral recognition have been studied. From investigations on the retention and resolution of structurally related compounds of uniconazole on γ-and β-cyclodextrin columns the benzene ring and alkyl group of the solute were found to play an important role in the formation of the CD complex and in the chiral recognition. Nuclear magnetic resonance data for the model systems of uniconazole and some analogs also supported these conclusions.
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    Chemical modification of a highly cross-linked di(methacryloyloxymethyl)naphthalene-divinylbenzene copolymer for HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 548-554 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyaromatic ester copolymer phases ; Polymer phases with C8 and C18 alkyl chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The Friedel-Crafts reaction has been used for chemical modification of a highly cross-linked di(methacryloyloxymethyl)naphthalene-divinylbenzene copolymer and the influence of the chemical modification on the chromatographic behaviour of the copolymer has been studied. The capacity factors and retention indices of five homologous series and test compounds were different on columns packed with modified and unmodified copolymers: the order of elution of the test compounds was indicative of significant differences between these and the unmodified copolymer. The porous structure of the modified copolymers was also observed to be different from that of the unmodified material.
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    URL: http://dx.doi.org/10.1007/BF02267915
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    Separation and quantitation of some metal ions by RP-HPLC using EDTA as complexing agent in mobile phase (1993)
    Springer
    Chromatographia 35 (1993), S. 621-626 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion pair formation ; Separation of anions and cations ; Metal speciation ; Optimization of separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ion pair reversed-phase high performance liquid chromatography has been used to achieve the simultaneous separation of some transition metal ions including Ni(II), Co(II), Cu(II), Mn(II), Fe(III), Pb(II), Cr(III), and Hg(II) as complexes of ethylenediaminetetraacetic acid (EDTA) originated, in the column itself. Due to the negative charge of the metal complexes, the separation of metal ions from inorganic anions such as Cr2O7 2− and NO3 − is possible by employing a positively charged counterion in the mobile phase. The influence of the nature and concentration of counterion, organic modifier content, ionic strength, EDTA concentration and pH of the mobile phase on the retention and selectivity has been investigated. Quantitation of metal ions was achieved with spectrophotometric detection. Detection limits ranged from 300 pg for Fe(III) to 35 ng for Cr(III) with a linearity of 2–3 orders of magnitude. Some applications of the technique to the separation of multielement mixtures are shown.
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    Reversed-phase high performance liquid chromatographic separation of nitrosamines: The use of the overlapping resolution mapping technique for the optimization of solvent compositions (1993)
    Springer
    Chromatographia 35 (1993), S. 671-674 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nitrosamines ; Overlapping resolution mapping ; Systematic optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes the overlapping resolution mapping procedure to determine optimum solvent compositions in the reversed-phase high performance liquid chromatography of nitrosamines. The procedure is successful in enabling the satisfactory resolution of all eight nitrosamines, some of which are listed as priority pollutants by the United States Environmental Protection Agency.
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    Chromatographic determination of position and configuration isomers of methyl oleate hydroxides from corresponding hydroperoxides (1993)
    Springer
    Chromatographia 36 (1993), S. 61-64 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Argentation thin-layer chromatography ; Solid phase extraction ; Fatty acid hydroperoxides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Studies of lipid oxidation usually employ such model systems as purified fatty-acid methyl ester. While methyl oleate hydroperoxides (MOPHs) can only be readily separated from the matrix by HPLC, because of their heat-susceptibility and relative instability, these same techniques are unable to separatecis MOHP fromtrans isomers. The present study reports an enhanced, rapid separation method forcis andtrans isomers of methyl oleate hydroxides, as well as HPLC determination of positional isomers per fraction of configuration isomer and isomer identification by gas chromatography-mass spectrometry.
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    URL: http://dx.doi.org/10.1007/BF02263838
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    Modelling chromatographic behaviour as a function of pH and solvent composition in RPLC (1993)
    Springer
    Chromatographia 36 (1993), S. 83-95 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention models ; Method development ; pH optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this work we establish the basic layout of IONICS, an expert system for optimizing the separation of ionogenic solutes in Reversed-Phase Liquid Chromatography, using the pH and the organic-modifier concentration of the mobile phase as parameters. We also present REMO, a front-end system that automates the retention modelling stage, based on a 9-parameter model. This system uses a scale transformation to suppress several numerical problems previously observed and features a strategy for automatic calculation of an initial approximation to the model optimum. The successful application of this system to a set of seven drugs is described. The final models are accurate and have smaller numerical problems. We also describe the use of a genetic algorithm instead of classical non-linear least-squares for fitting the model to the experimental data. Results indicate that genetic algorithms are a valuable, complementary tool for retention modelling.
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    Sequential optimisation of the separation of a complex mixture of plastics additives by HPLC with a quaternary gradient and a dual detection system (1993)
    Springer
    Chromatographia 36 (1993), S. 135-143 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Plastics additives ; Optimization ; Elution gradient ; Light-scattering detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of two families of plastics additives (phenolic antioxidants and UV absorbers) has been achieved by high performance liquid chromatography with a quaternary gradient. A methodology of separation based on a sequential optimization is described. After a preliminary study of the effects of solvents on retention of compounds, the mobile phase is first chosen for each class of additives (Irganox and Tinuvin), then for the mixture of all the compounds and the separation is finally optimized. The importance of the column phase ratio is also reported. The use of two detectors, UV absorbance and light-scattering, enables all the compounds to be detected. The performance of the detectors has been compared and the effects of the nebulization temperature on the detection of low molecular mass compounds is reported.
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    Optimization of a multisolvent composition in RP-HPLC: Convenient criterion for preliminary search for the best eluent strength (1993)
    Springer
    Chromatographia 36 (1993), S. 157-163 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Multisolvent mobile phase ; Solvent optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Interpretive methods are very commonly used to direct the search for the optimum solvent composition. For multisolvent systems, the composition search space is often reduced to one straight line (ternary systems with two organic modifiers), three straight lines (three ternary systems with each possible pair of the organic modifiers of the tetrahedron) — or a plane delimited by a triangle (quaternary systems inside the solvent tetrahedron). In each case, the space is restricted by binary compositions of equal solvent strength, in such a way that through it, the analysis time remains approximately constant. This restricted space is defined without taking into account any selectivity criterion between peaks, and consequently, if a given pair of peaks is badly resolved with the considered binary solvents, the probability of any mixture of them improving the peak selectivity will be very low. The ability to calculate the retention models in a binary solvent system from two linear gradient runs, allows the prediction of the selectivity for each pair of solutes into each binary solvent system (ACN/Water, MeOH/Water, THF/Water) from six preliminary linear gradient runs, and then, to determine and eliminate all the sets of isoeluotropic binary compositions that will offer little hope of giving useful separation conditions with multisolvent systems and, at the same time, to select the most promising set of binary compositions. The selectivity and the total time of the chromatogram are the two parameters that are considered for this search. When several possiblities are found, priority is given to the simplest solvent system (binary rather than ternary and ternary rather than quaternary). Reducing the number of preliminary experiments and improving the accuracy of the predicted optimum are the two objectives of this approach. Its practical interest is discussed by comparing the results obtained for an illustrative separation to those obtained with another existing method.
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    Determination of pyromellitic acid in aqueous matrices by HPLC (1993)
    Springer
    Chromatographia 36 (1993), S. 365-367 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pyromellitic acid ; Migration tests ; Food simulants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method for the HPLC determination of pyromellitic acid in aqueous media used as “food simulants” has been developed and is described in this paper. The proposed method can determine pyromellitic acid at ppb trace levels and is based on an ionic exchange separation mechanism. The method herein developed has been applied to the determination of pyromellitic acid residues leached from plastic bottles.
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    URL: http://dx.doi.org/10.1007/BF02263894
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    Method development and validation procedure for the chromatographic assay of cocaine and its metabolites in pharmacokinetic studies (1993)
    Springer
    Chromatographia 36 (1993), S. 368-372 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chromatographic assay ; Validation ; Cocaine and its metabolites ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Although chromatographic assay is one of the most powerful methods of analysing cocaine and its metabolites in blood samples, the methods presently available for the separation of the metabolites suffer from problems with long-term use for large numbers of assays. We describe the development of a method and devote special attention to the description of the validation procedures of each step of the assay. The validation procedures can be described in two parts. The first is the development of the separation by reversed phase HPLC using the retention properties of cocaine and its major metabolites norcocaine, benzoylecgonine, norbenzoylecgonine as affected by the strength, selectivity and pH of the mobile phase. On a C18, end-capped column, on-column band broadening was limited to the extent that all pairs of peaks are resolved. Extraction from plasma was performed with C18 Bond-Elut and good recovery obtained, without interferences, for all the products under study (cocaine recovery 90.9±6.3%). The internal standard method using atropine has been used for the assay. Validation procedures enbled quantification of cocaine and its main metabolites at concentrations between 50 and 2000 ng/ml.
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    Urinary hydroxylysine glycosides: Solid phase extraction and reversed phase chromatographic measurement (1993)
    Springer
    Chromatographia 36 (1993), S. 144-146 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydroxylysine glycosides ; Solid phase extraction ; Collagen ; Osteoporosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is described for measurement of urinary hydroxylysine glycosides (galactosyl-hydroxylysine, or GHYL, and glucosyl-galactosyl-hydroxylysine, or GGHYL) by reversed phase chromatography after purification of the sample by solid phase extraction. Urinary levels of hydroxylysine glycosides has been correlated with collagen catabolism, and the urinary GGHYL: GHYL ratio is indicative of the metabolism of connective tissue. The GGHYL:GHYL ratio might, therefore, be a promising indicator of bone mass loss. The method described is analytically reliable and enables the measurement of a possible marker for diagnosis and follow-up of osteoporosis.
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    URL: http://dx.doi.org/10.1007/BF02263851
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    Comparison of the retention behaviour of phenol derivatives on porous graphitized and octadecylsilica columns (1993)
    Springer
    Chromatographia 36 (1993), S. 19-26 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structure-retention relationships ; Mathematical data analysis ; Phenol derivatives ; ODS and graphitized carbon columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of 22 ring-substituted phenol derivatives on porous graphitized carbon (PGC) (eluents: acetonitrile — water and methanol — water mixtures) and on octadecylsilica (ODS) (eluents: methanol — 0.025 M KH2PO4 mixtures) was determined, and the relationship between retention and physicochemical parameters were evaluated by principal component analysis followed by two-dimensional nonlinear mapping and by cluster analysis as well as by canonical correlation analysis. Calculations proved that marked differences can be detected between the retention characteristics of PGC and ODS columns, and the electronic parameters of phenol derivatives have the highest impact on their retention. The comparison of various multivariate mathematical-statistical methods indicated that principal component analysis followed by two dimensional non-linear mapping is the most appropriate method for the evaluation of large data matrices in RP-HPLC.
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    URL: http://dx.doi.org/10.1007/BF02263830
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    The calculation of retention and selectivity in reversed-phase liquid chromatography II. Methanol-water eluents (1993)
    Springer
    Chromatographia 36 (1993), S. 39-42 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structure-retention relationships ; Column parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary To calculate retention in reversed-phase, high-performance liquid chromatography a method based on the molecular structure of the analyte and the characteristics of sorbents and mobile phases has been employed. Characteristics of different ODS-columns in water-methanol eluents have been determined.
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    URL: http://dx.doi.org/10.1007/BF02263833
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    Trace enrichment of polar pollutants from water and the influence of humic substances (1993)
    Springer
    Chromatographia 37 (1993), S. 13-19 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polar pollutants in water ; On-line trace enrichment ; Humic substances
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A practical liquid chromatographic early-warning system for polar pollutants in water ought to have detection limits at a level below a microgram per litre. Using ultraviolet absorbance detection this normally necessitates trace enrichment of the samples. In this study ten different sorbents have been tested with respect to their enrichment capacity. The hydrophobic polymeric PLRP-S material, in combination with a C-18 modified analytical column, proved to be the best choice. The influence of humic substances, present in surface water, was also studied. Lowering of the sample pH, resulted in a significant increase in the interferences due to the humic substances.
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    URL: http://dx.doi.org/10.1007/BF02272181
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    Determination of free amino acids in tobacco by HPLC with fluorescence detection and precolumn derivatization (1993)
    Springer
    Chromatographia 37 (1993), S. 593-598 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino acids ; Tobacco ; Pre-column derivatization ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method for the determination of primary amino acids in tobacco, based on precolumn derivatization with the fluorogenic reagent naphthalene-2,3-dicarboxaldehyde, is described. Sample preparation consists of a single step of extraction with waterethanol (1∶1, v/v) at ambient temperature (assisted by sonication), followed by filtration of an aliquot and addition of derivatization reagents. High performance liquid chromatographic separation of the derivatized amino acids is performed on a Novapak C-18 column using fluorescence detection with excitation and emission wavelengths set at 246 and 470 nm respectively. Extraction efficiency, matrix interferences and other important variables are studied. This method has been used to analyze different types of tobaccos including burley, bright and oriental with satisfactory results.
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    URL: http://dx.doi.org/10.1007/BF02274107
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    Rapid analysis of biopolymers on modified non-porous polystyrene-divinylbenzene particles (1993)
    Springer
    Chromatographia 37 (1993), S. 653-658 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Styrene-DVB polymer phases ; Proteins and oligonucleotides ; Polymerase chain reaction ; Rapid separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of short columns packed with alkylated nonporous 2.1 μm polystyrene — divinylbenzene particles has enabled the efficient separation of proteins, oligonucleotides, and DNA fragments in less than 60 seconds. An increase in the flow-rate resulted in only a minor reduction in the resolution of the proteins. Careful temperature control and small gradient dead volume were essential if reproducible quantitative results were to be achieved. Analysis at elevated temperatures not only reduced the viscosity of the eleents and, hence, column back-pressure but also resulted in higher column efficiency. The best resolution of proteins was achieved by performing the separation at 80°C whereas the optimum temperatures for the separation of oligonucleotides and DNA fragments ranged from 40–50°C. High speed analysis was used both to control the purity of oligonucleotides following automated solid-phase synthesis and to evaluate the expression of multidrug resistance genes in patients suffering from chronic lymphatic leukemia.
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    URL: http://dx.doi.org/10.1007/BF02274118
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    Liquid chromatography — Particle beam mass spectrometry for identification of unknown pollutants in water (1993)
    Springer
    Chromatographia 37 (1993), S. 159-167 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Particle beam interface-mass spectrometry ; Water analysis and identification of unknown ; pollutants ; Phenylurea herbicides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Trace enrichment on a precolumn packed with copolymer material, coupled on-line with reversed-phase, column liquid chromatography-particle beammass spectrometry (RPLC-PB-MS) has been used for both target and non-target analysis of water samples. RPLC is carried out on a C-18-bonded silica column using a linear acetonitrile-0.1 M ammonium acetate gradient. Using optimised PB-MS conditions and 100–250 ml water samples, the detection limits for several phenylureas are in the 0.03–0.05 μg l−1 range using the full-scan mode; repeatability is good and the LC-PB-MS system is robust. Several surface and drinking water samples have been analysed and low levels of various environmental contaminants have been identified using electron impact mass spectra. Applying chemical ionisation with methane as reagent gas in both the positive and negative mode in conjunction with PB-MS provides relevant confirmatory information.
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    URL: http://dx.doi.org/10.1007/BF02275854
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    Quantification of 2,4-dinitrophenyl-hydrazones of low molecular mass aldehydes and ketones using HPLC (1993)
    Springer
    Chromatographia 37 (1993), S. 185-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aldehydes ; Ketones ; Dinitrophenylhydrazones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This study was undertaken to evaluate the HPLC separation and quantification of several low molecular mass aldehydes and ketones, which may be produced during combustion in alcohol-fueled automobiles, by means of their dinitrophenylhydrazone derivatives. Stationary phases (ODS), mobile phase components (acetonitrile or methanol with water) and detection sensitivity at 254 and 365 nm were evaluated. Separation of eight dinitrophenylhydrazones could be achieved in approximately 20 minutes using a Zorbax ODS or a Supelcosil LC-PAH column with a MeOH:H2O (75∶25 v/v) mobile phase. Complete separations were not obtained with either a Nova-Pack C-18 or an Ultrasphere ODS column. The use of acetonitrile-water mobile phases produces poorer resolution at all compositions tested. Quantification of the compounds by several methods was compared, with the lowest standard deviations being seen with the external than 1.5 pmol for each of the 2,4-dinitrophenylhydrazones in the test solution. The method is being applied to the analysis of aldehydes and ketones in the exhaust of automobile engines fueled by ethanolgasoline mixtures.
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    URL: http://dx.doi.org/10.1007/BF02275859
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    Determination of fluoroquinolone antibacterials as N-acyl derivatives (1993)
    Springer
    Chromatographia 37 (1993), S. 295-299 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoroquinolones ; N-Acyl derivatives of fluoroquinolones ; Retention vs, structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple and quantitative method for the preparation and high performance liquid chromatography (HPLC) of N-acylated fluoroquinolones has been developed. The acylation procedure was performed with four different acid anhydrides and found to be applicable to several fluoroquinolones. The acylated derivatives were chromatographed directly on a Nucleosil C18 column without the necessity of further sample manipulation. Detector response for the N-acetyl derivatives of norfloxacin, ciprofloxacin, sarafloxacin, and temafloxacin was linear to at least 50 μg/mL. The retention behavior of the N-acyl derivatives can be predicted by the length of the carbon chain of the amide.
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    URL: http://dx.doi.org/10.1007/BF02278637
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    LC clean-up and GC/MS analysis of polycyclic aromatic hydrocarbons in river sediment (1993)
    Springer
    Chromatographia 37 (1993), S. 381-386 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography-mass spectrometry ; River sediments ; Polynuclear aromatic hydrocarbons (PAHs) ; Dinitroanilinopropyl-silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An LC clean-up procedure based upon a complexation between polycyclic aromatic hydrocarbons (PAHs) and silica with chemically bonded 2,4-dinitroaniline has been combined with GC/MS. The LC pre-separation makes it possible to obtain a relatively clean fraction of PAHs free from alkanes, alkylbenzenes and naphthalenes, PCBs, chlorinated pesticides and many other interfering compounds. This fraction has been analyzed using capillary GC and mass selective detector (MSD). Substantial improvement of the MS spectra of PAHs with three or more fused benzene rings is achieved.
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    URL: http://dx.doi.org/10.1007/BF02272252
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    Trace-level monitoring of chloroanilines in environmental waters using on-line trace-enrichment and liquid chromatography with UV and electrochemical detection (1993)
    Springer
    Chromatographia 37 (1993), S. 392-398 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line trace-enrichment ; Chloroanilines in water ; Electrochemical and UV detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An on-line procedure is described for the trace-level determination of mono-, di- and methyl-chloroanilines in aqueous samples using selective preconcentration with a cation-exchanger and liquid chromatography with UV and electrochemical detection. Because direct percolation through a cation-exchanger has to be avoided owing to the high content of inorganic anions present in natural waters, a two-step on-line preconcentration was carried out: chloroanilines were first trapped on a precolumn packed with an apolar polymeric sorbent (PRP-1) in their neutral form. Then the PRP-1 precolumn was coupled in series with a second precolumn containing cation exchange material. The chloroanilines were removed from the first precolumn with 3 mL of deionised water: acetonitrile (3∶1) at pH 1 and retained by the cation exchange column. The contents of the cation exchange column were finally desorbed onto the analytical column and eluted with a water: acetonitrile gradient. The combination of selective trace enrichment and sensitive electrochemical detection allows the simultaneous determination of chloroanilines from 150 mL of river water samples with detection limits below 30 ng/l. Identification is confirmed by the selective preconcentration and the two detection modes.
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    URL: http://dx.doi.org/10.1007/BF02272254
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    Preparation of chemically bonded stationary phases for HPLC by anin situ process (1993)
    Springer
    Chromatographia 37 (1993), S. 505-510 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases ; In-situ bonding ; Coverage density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improvedin situ process for preparing chemically bonded stationary phases for HPLC direction packed silica columns has been developed. For this purpose, a modified home-made HPLC pump was used. The different parameters of the process, such as, type of silane, temperature, flow rate and concentration, have been studied to define an operational and reproducible procedure for bonding in analytical columns. In thein situ process, the sequence of silane reactivities was RSi−H≫RSi−NEt2≥RSi−Cl. Stationary phases obtained are compared to those from the usual batch process.
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    Separation of anthranilate derivatives of sugars by reverse-phase chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 543-545 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Anthranilate derivatives ; UV chromophores
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Precolumn derivatisation of sugars with isatoic anhydride forms anthranilate derivatives. The anthraniloyl derivative imparts a UV chromophoric group and also hydrophobicity to the compound which makes it useful for separation and detection of sugars by reverse-phase chromatography. This was found to be a cheap and easy method for separation and detection of sugars.
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    Determination of methyl anthranilate and methyl N-methylanthranilate in beverages by liquid chromatography with fluorescence detection (1993)
    Springer
    Chromatographia 35 (1993), S. 681-684 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methyl anthranilate ; Methyl N-methylanthranilate ; Beverages ; Fluorimetric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase HPLC method for the separation and determination of two anthranilic acid derivative esters, methyl anthranilate and methyl N-methylanthranilate, has been developed. These esters are aromatic compounds of wines and fruits. A gradient elution technique, using methanol: water changing from 40∶60 to 80∶20 mixtures, is used to decrease the analysis time. The sensitivity of the determination is improved by using fluorescence detection. The proposed method is applied to the determination of the esters in wines, brandies, grape beverages and fruit juices.
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    An HPLC study of tinidazole hydrolysis (1993)
    Springer
    Chromatographia 36 (1993), S. 79-82 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tinidazole ; Hydrolysis ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The high-performance liquid chromatographic (HPLC) method herein described allows the simultaneous determination of the hydrolysis kinetics of tinidazole and the formation kinetics of the hydrolysis products. Tinidazole is easily hydrolysed under basic conditions at raised temperature. The rate varies with the pH and the temperature of the solution, and the decomposition follows apparent first-order kinetics. The Arrheinius equation can be used to describe the effect of temperature on the half-life.
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    URL: http://dx.doi.org/10.1007/BF02263842
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    Pre-column fluorescence derivatization of peptides containing arginine aldehyde moiety in high-performance liquid chromatography (1993)
    Springer
    Chromatographia 36 (1993), S. 105-109 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-column fluorescence derivatization ; Arginine-aldehyde peptide ; LY-294468
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive reversed-phase high-performance liquid chromatographic method with pre-column fluorescence derivatization has been developed for the determination of DLL-MePhe-Pro-Arg-H (LY-DLL, LY-294468). In the search for a derivatization method for the determination of the tripeptide aldehyde, which is present in equilibrium structures in aqueous solution, it was found that the guanidino group of the argininal residue was not converted into a fluorescent derivative by reaction with benzoin. However, if the LY-DLL was first converted into a LY-DLL-TRIS adduct, a fluorescent product could be obtained by the reaction of LY-DLL with TRIS in TRIS(HCl) buffer (pH 8.5) followed by benzoin in the presence of beta-mercaptoethanol and sodium sulphite in an alkaline medium.
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    Evaluation ofo-phthalaldehyde as bifunctional fluorogenic post-column reagent for glutathione in LC (1993)
    Springer
    Chromatographia 36 (1993), S. 130-134 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Glutathione ; o-Phthalaldehyde ; Post-column derivatization ; Plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the assay of various forms of glutathione in human plasma has been developed. The reduced form was measured after direct injection of deproteinized plasma with perchloric acid. The unbound oxidized forms were assayed in deproteinized plasma after reduction with dithiothreitol. The total amount of glutathione was determined by reduction before protein precipitation. Separation of reduced glutathione from other endogenous thiols was by ion-pair, reversed-phase, high-performance liquid chromatography. Post-column derivatization withortho-phthalaldehyde made the assay more selective than when using pyrenemaleimide as thiol fluorogenic reagent. The linear range was 0.02 to 2.0 μg mL−1 with good repeatability (relative standard deviation less than 5% for the lowest concentration measured).
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    Effect of drying temperature and blanching on the degradation of chlorophyll a and b in mint (Mentha spicata Huds.) and basil (Ocimum basilicum): Analysis by high performance liquid chromatography with photodiode array detection (1993)
    Springer
    Chromatographia 36 (1993), S. 152-156 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photodiode array detection ; Chlorophylls ; Pheophytins ; Drying ; Mint (Mentha spicata Huds.) ; Basil (Ocimum basilicum)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of drying conditions on the preservation of chlorophyll pigments in mint and basil have been investigated in order to determine the effects of drying temperature and whether or not there was a prior blanching. Pigments extracted from fresh and dried samples were analyzed by reversed phase high performance liquid chromatography coupled to a photodiode array detector; isocratic separation was performed on a Zorbax ODS C18 column. The purity of the chromatographic peaks of chlorophylls and breakdown products was investigated. The visible spectra of standard samples of chlorophylls and pheophytins were compared, using least squares normalization with those of peaks from the extracts of fresh and dried mint and basil. The study has shown that chlorophylls were better preserved when drying was preceded by a short blanching; if samples were not blanched before drying, the degradation of chlorophylls a and b was best prevented by drying at low temperatures.
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    Determination of sulbutiamine and its disulfide derivatives in human plasma by HPLC using on-line post-column reactors and fluorimetric detection (1993)
    Springer
    Chromatographia 36 (1993), S. 167-173 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid-phase extraction ; On-line post-column reaction ; Sulbutiamine ; Thiamine disulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new direct HPLC procedure for the simultaneous determination of sulbutiamine (Arcalion) and other thiamine disulfides in human plasma has been developed. The method involves an automated solidphase extraction on octadecylsilyl (C18) cartridges and chromatographic separation of the compounds on an RP Select B column with gradient elution using methanol and phosphate buffer. Detection was by fluorescence of the resulting thiochromes obtained from two on-line post-column reactors. Optimization of post-column reaction parameters has been achieved. This method has been proved to be highly selective for the determination of the thiamine disulfide derivatives and quantitation limits of 5 ng·ml−1 were obtained for each compound in human plasma. Linearity was in the range 5–200 ng·ml−1. Precision and accuracy were also demonstrated by within-day and between-day assays, and showed the good reliability of the method.
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    Simultaneous assay of platelet and plasma catecholamines by HPLC with coulometric detection (1993)
    Springer
    Chromatographia 36 (1993), S. 164-166 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Platelet ; Catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Platelets and monoaminergic neurons share many morphological, biochemical, and pharmacological properties. In addition to its similarities to serotonergic nerve endings, the platelet has also been considered a good model for the study of the noradrenergic function, since it can selectively take up, store, and release norepinephrine (NE). In this study platelet and plasma levels of free catecholamines (CA) in 20 healthy subjects have been determined by HPLC with a reversed phase (C18) ionpairing system equipped with a coulometric detector. Direct correlation was observed between platelet and plasma levels of NE. A positive correlation was also found between the age of the sujects and both platelet and plasma NE levels. While showing that the peripheral noradrenergic hyperactivity of the elderly is also reflected in platelet NE content, this study also demonstrates that simultaneous assay of platelet and plasma CAs can be a useful tool for an integrated and more complete evaluation of sympathetic nervous system activity.
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    Retention properties of cyclodextrins and modified cyclodextrins in reversed phase HPLC (1993)
    Springer
    Chromatographia 36 (1993), S. 174-178 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Binary solvent systems ; Cyclodextrin and modified Cyclodextrin ; Solubility ; Hydrophoby
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In the course of systematic studies on the solubility, hydrophobicity and complexation properties of cyclodextrins and modified cyclodextrins, the retention behavior of α, β, γ and of some glycosylated cyclodextrins has been examined by means of reverse phase HPLC. Mobile phase mixtures containing large amounts of water have been used because of the possible application of such systems to biological studies. Mobile phase mixtures with both methanol and acetonitrile show a linear relationship between the volume fraction of the organic part of the mobile phase and the logarithm of the capacity factor. The extrapolation of capacity factors to a total aquous system are used and compared to other techniques (including solubility) in order to evaluate the hydrophobic properties of the cyclodextrins. In particular, the solubility of cyclodextrins has been explored for a wide range of organic solvent/water mixtures. Whilst β cyclodextrins are definitely the most hydrophobic, followed by glycosylated β cyclodextrins, the others behave differently in the two mobile phase systems. The differences observed in the results are related to the chemical nature of the organic phase. Comparisons between chromatographic and solubility methods are given and interpretations are proposed. Some cyclodextrins have been modified to increase or modify not only the hydrophobicity but also the solubility, the complexation and the molecular recognition of drugs. The most important aim of this study was to define conditions and rules for further drug vectorization by cyclodextrin-drug complexation.
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    Coupled liquid-liquid extraction and column switching LC for the determination of a new antihistaminic H1 drug in human urine (1993)
    Springer
    Chromatographia 36 (1993), S. 337-342 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid-extraction ; Column switching ; Antithistaminic H1 ; Benzimidazole derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Mizolastine (SL 85.0324) is a new antihistaminic H1 benzimidazole derivative which is excreted into urine almost completely metabolized; about 2% of the unchanged drug is excreted as conjugated compound which requires enzymatic deconjugation before analysis. Since the existing methods for plasma samples do not work on deconjugated human urine due to interferences, a new method was developed. The method is based on a diethyl-ether extraction of mizolastine and an internal standard from alkalinized urine. The ether extract is back-extracted with an aqueous buffer (pH=2.6), this extract is neutralized (pH=6.5) and an aliquot injected into a C18 pre-column where clean up and preconcentration take place. The analytes are then desorbed from the pre-column and transferred to the analytical column. The analytical column is a C18 type specially seactivated for basic compounds with an eluent of acetonitrile/phosphate solution (pH=4.5), 40/60, v/v, at a flow rate of 1 ml min−1. Detection is at 285 nm. The method is linear in the range 10–500 ng ml−1 with a lower limit of detection of 10 ng ml−1. The precision and accuracy, evaluated during intra-day and inter-day assays, are satisfactory for pharmacokinetic investigations.
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    Enzyme based detection systems in column liquid chromatography — Extension of selectivity and sensitivity (1993)
    Springer
    Chromatographia 36 (1993), S. 381-398 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enzyme detection systems ; Mass spectrometry ; Fermentation ; Carbohydrates, amino acids, aldehydes, catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Enzyme based detection systems in column liquid chromatography are described using systems based on both enzyme reactors in conjunction with a flow through detection device and enzyme electrodes. Optimizations for making detection principles compatible with chromatographic systems and applications made in our laboratories are presented for the analysis of e.g. carbohydrates, amino acids, ethanol and catecholamines. Gel-permeation chromatography and mass spectrometry are used as complementary techniques for qualitative and quantitative analysis of complex samples.
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    URL: http://dx.doi.org/10.1007/BF02263897
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    Reversible solvent and temperature induced “monomeric-like” —“Polymeric-like” transitions in alkyl bonded silica (1993)
    Springer
    Chromatographia 36 (1993), S. 11-18 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polyfunctional and monofunctional phases ; Retention mechanisms ; Homologous series ; Reversible transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The study of behaviour of homologous series (and more precisely, the plots of methylene selectivity versus the carbon number, n, of the alkyl chain of the homologue) on monomeric and polymeric phases in liquid chromatography enabled us to characterize two kinds of retention mechanism. These mechanisms are not independent; changes in the temperature or mobile phase composition allow passage from one to the other. The first, for which the methylene selectivity versus n decreases with a discontinuity, defines a retention mechanism where solutes are inserted between the grafted chains. It occurs for monomeric phases at ambient temperature, for polymeric phases, at high temperature or with a strong solvent like THF, CH2Cl2, AcMe or CHCl3. The second gives a plot of methylene selectivity versus n with a maximum. It is consistent with a partition mechanism with total immersion of the solute in the bed of the stationary phase. It occurs for a polymeric phase at ambient temperature or for a monomeric one at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263829
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    Application of totally automated on-line sample clean up for prostanoid extraction and HPLC separation (1993)
    Springer
    Chromatographia 36 (1993), S. 33-38 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Prostaglandins ; C18 Solid phase extraction ; Radioimmunoanalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The aim of this study has been the evaluation of an automated system for on-line sample preparation using solid phase extraction and HPLC purification for the measurement of prostanoids in urine. We have established the optimum precolumn and column conditions for this analysis. The manual extraction —HPLC procedure furnishes lower recoveries and higher coefficients of variation than those obtained by the automated on-line procedure. The automated system has been applied to prostanoid analysis of human urine samples from subjects exposed to lead.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263832
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    Control of adsorption and solubility in gradient high performance liquid chromatography 1. Principles of sudden transition gradients and elution characteristics of copolymers from styrene and methacrylates (1993)
    Springer
    Chromatographia 37 (1993), S. 7-12 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methacrylates) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Proper retention of polymers in high performance liquid chromatography often requires injection into a starting eluent which is not a solvent for the sample under investigation. In this case, the polymer is precipitated at the top of the column. Subsequent gradient elution has to be performed by addition of an eluent with sufficient chromatographic strength and solvent power. In normal phase chromatography, it must be a solvent of high polarity. With the gradient elutions reported so far, polarity and dissolution power were simultaneously increased. The present paper reports the separate control of solvent strength and chromatographic power by applying gradient programs which include sudden addition of a moderately polar solvent. The amount of the latter does not suffice for elution, which is performed by subsequent, controlled addition of a highly polar nonsolvent. Sudden transition gradients of this kind work with, e.g.,iso-octane as a nonpolar starting eluent, tetrahydrofuran as a solvent of intermediate polarity, and methanol as a strongly polar nonsolvent. They have been applied to copolymers from styrene and ethyl methacrylate, methyl methacrylate, or methoxyethyl methacrylate.
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    URL: http://dx.doi.org/10.1007/BF02272180
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    Single step LC method for determination of folypolyglutamate synthetase activity and separation of polyglutamates (1993)
    Springer
    Chromatographia 37 (1993), S. 73-78 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Folylpolyglutamate synthetase ; Folate polyglutamates ; L5178Y cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC assay has been developed for measuring folylpolyglutamate synthetase (FPGS) activity. It is based on the incorporation of U(14C)-glutamic acid into a folate derivative. The method has the advantage over previous procedures of offering in a single step full separation of the unreacted U(14C)-glutamic acid from that incorporated in folylpolyglutamates, as well as the possibility of identifying the chain length of the polyglutamates formed. It has been applied to determine FPGS activity in murine leukaemic lymphoblasts L5178Y. Activity was proportional over a wide range both to the incubation time and the amount of protein. Maximum activity was observed with folinic acid and the antifolate aminopterin (AMT) as substrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02272192
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    Reversed phase liquid chromatography of some benzimidazole derivatives (1993)
    Springer
    Chromatographia 37 (1993), S. 98-104 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin layer chromatography ; Benzimidazole ; Retention behaviour in RP systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of a series of benzimidazole derivatives has been studied as a function of the water content of aqueous methanol and aqueous acetonitrile eluents. The relationship between the retention constant (log k) and the pH of the aqueous phase was linear, with slope values depending on the composition of the aqueous phase, the molecular structure of the compound, and the type of C-18 bonded stationary phase. The type of organic modifier significantly affected the shape of the relationship between log k and the volume fraction of organic modifier in the mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02272196
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    Simultaneous determination of Ibuproxam and Ibuprofen in human plasma by HPLC with column switching (1993)
    Springer
    Chromatographia 37 (1993), S. 618-622 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ibuproxam and Ibuprofen in plasma ; Column switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new high-performance liquid chromatographic method with column switching has been developed for the simultaneous determination of Ibuproxam and its metabolite Ibuprofen in plasma. The plasma samples were injected onto a LiChrosorb RP-8 precolumn after dilution with an internal standard solution in phosphoric acid. Polar plasma components were eluted with 0.05 M phosphoric acid. After valve switching, the concentrated drugs were eluted in the back-flush mode and separated on an Inertsil ODS-2-column with acetonitrile-methanolphosphate buffer as mobile phase. The method showed excellent precision, accuracy and speed with detection limit of 0.1 μg ml−1. Total analysis time per sample was less than 30 min and the coefficients of variation for intra and inter-assay were less than 3.5%. This method has been successfully applied to plasma samples from human volunteers after oral administration of Ibuproxam.
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    URL: http://dx.doi.org/10.1007/BF02274112
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    Synthesis and mechanistic study of novel π-basic chiral stationary phases derived from tyrosine (1993)
    Springer
    Chromatographia 37 (1993), S. 433-443 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Supercritical fluid chromatography ; Chiral stationary phases ; Chiral recognition mechanism ; Factorial design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This work was a study of novel π-basic, chiral stationary phases (CSPs) deriving from tyrosine and bearing two stereogenic centres. These CSPs differ in the nature of the amidic substituent (n-butyl ortert-butyl) and by the configuration of both the chiral centres (S or R). The enantioselectivity and elution order of various 3, 5-dinitrobenzoyl derivatives were studied using liquid and supercritical fluid chromatographic modes. The chromatographic data allowed determination of the influence of the CSP structure (also studied according to factorial designs) and determination of the influence of the solute structure. Chiral recognition mechanisms which are in good agreement with these observations are proposed. Finally, this paper reports the enantiomeric resolution of two compounds of pharmaceutical interest (warfarin and ICI 176334).
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    URL: http://dx.doi.org/10.1007/BF02272261
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    125I-labelled aprotinin as reagent for simultaneous determination of serine proteinases by hydrophobic interaction chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 471-474 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction chromatography ; 125I-labelled aprotinin ; Serine proteinases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A previously described method for determining more than one serine proteinase simultaneously by hydrophobic interaction chromatography of their complexes with aprotinin is inapplicable when other UV-absorbing species are co-eluted. The suitability of125I-labelled aprotinin has therefore been tested as a reagent in the analysis of mixtures containing trypsin, α-chymotrypsin and kallikrein taken as models, in the presence of ribonuclease and lysozyme. A new procedure is described which, without introducing changes in the chromatographic separation, allows direct determination of serine proteinases in terms of molarity. Results obtained in experiments with solutions containing from 0.20 to 30.00 nmol of each serine proteinase are reported.
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    URL: http://dx.doi.org/10.1007/BF02275781
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    Separation of paralytic shellfish toxins by reversed phase high performance liquid chromatography, with postcolumn reaction and fluorimetric detection (1993)
    Springer
    Chromatographia 35 (1993), S. 613-620 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion pairing ; Paralytic shellfish toxins ; Dinoflagellate cultures ; Toxic molluscs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An RP-HPLC method for the separation of shellfish toxins is described, employing three isocratic systems: Octanesulfonic acid in ammonium phosphate buffer plus acetonitrile for the separation of carbamate toxins (neoSTX, dcSTX and STX), octansulfonic acid in ammonium phosphate buffer for the separation of GTXs and tetrabutylammonium in the same buffer for Cs separation. These eluents perform the separation prior to postcolumn reaction and fluorimetric detection. The procedures have been applied to the determination of toxin production in dinoflagellate cultures, field samples of red tides, and toxic mussels.
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    URL: http://dx.doi.org/10.1007/BF02267925
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    High performance liquid chromatography of chlorophylls c3, c1, c2 and a and of carotenoids of chromophyte algae on a polymeric octadecyl silica column (1993)
    Springer
    Chromatographia 35 (1993), S. 543-547 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophyll c pigments ; Chromophyte algae ; Monomeric and polymeric ODS phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Photosynthetic pigments from chromophyte marine algae were analyzed using three different commercial columns with ODS stationary phases of different degrees of polymerization. No separation of chlorophylls c1 and c2 could be achieved using monomeric or intermediate stationary phases, even at subambient temperatures. As with other planar compounds, the polymeric stationary phase showed the highest selectivity for chlorophyll c pigments, allowing the simultaneous separation of chlorophylls c3, c1 and c2 and other pigments occurring in chromophyte algae by using a binary gradient starting with a highly buffered mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02267914
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    Determination of urinary organic acids by HPLC (1993)
    Springer
    Chromatographia 36 (1993), S. 53-56 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Urinary organic acids ; Creatinine ; Aromatic solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method for the simultaneous determination of urinary organic acids and creatinine for following the metabolism of aromatic solvents is reported. After extraction of acidified, filtered urine with diethylether followed by evaporation, the dried residue is dissolved in mobile phase. Hydroxybenzoic acid is used as internal standard. A column of Nucleosil C18 is used with a precolumn of the same material. The mobile phase is acetonitrilephosphate buffer, pH 3.3 (17∶83). For determination of creatinine the sample is simply diluted 10-fold and the eluate monitored at 215 nm (UV). This technique gives highly reproducible results and is simple, reliable and useful for biological monitoring.
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    URL: http://dx.doi.org/10.1007/BF02263836
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    HPLC fluorescence determination of nitrites in water using precolumn derivatization with 4-methyl-7-aminocoumarin (1993)
    Springer
    Chromatographia 36 (1993), S. 57-60 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Nitrites ; Fluorescence ; Precolumn derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid, simple, and sensitive method is described for determination of nitrites in water. Nitrite (NO2−) ions react with coumarin 120® (4-methyl-7-aminocoumarin) in sulfuric acid medium to give the corresponding 7-diazo compound. After hydrolysis, this latter yields (95%) the highly fluorescent 4-methyl-7-hydroxycoumarin (4-methylumbelliferone) which is fluorimetrically detected at 380 nm after excitation at 325 nm. In order to avoid interference from both excess coumarin 120® and the trace amounts of 4-methylumbelliferone which occurs in coumarin 120® as an impurity, use of HPLC is mandatory; a satisfactory separation is obtained on a cyano stationary phase with apolar hexane-isopropanol (95∶5, v/v) as eluent. Under these conditions, linearity of response is obtained from 1 to 30 μg.L−1 of NO2−; the limit of detection is 0.5 μg.L−1. The repeatability and reproducibility, expressed as RSD %, are 2.5 and 4.7 % respectively, for n=6 and 5 μg.L−, analytical characteristics which demonstrate the reliability of the proposed method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263837
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