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  • Column liquid chromatography  (193)
  • Analytical Chemistry and Spectroscopy
  • Chemical Engineering
  • Humans
  • Springer  (196)
  • 1990-1994  (196)
  • 1980-1984
  • 1925-1929
  • 1992  (88)
  • 1990  (108)
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  • 1990-1994  (196)
  • 1980-1984
  • 1925-1929
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular evolution 35 (1992), S. 7-16 
    ISSN: 1432-1432
    Keywords: Alu source genes ; Humans ; Gorillas ; Retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A member of the young PV Alu sub-family is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
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  • 2
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    Journal of molecular evolution 34 (1992), S. 336-344 
    ISSN: 1432-1432
    Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.
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  • 3
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    International journal of biometeorology 34 (1990), S. 42-48 
    ISSN: 1432-1254
    Keywords: Briths ; Humans ; Solar wind ; Geomagnetism ; Melatonin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract Data obtained from the literature on the annual pattern of human conceptions and plasma melatonin at high latitudes indicated that simple annual rhythms do not exist. Instead, prominent semiannual rhythms are found, with equinoctial troughs and solsticial peaks. A prominent semiannual environmental event is the magnetic disturbance induced by the solar wind. The semiannual magnetic disturbances are worldwide, but most pronounced in the auroral zones where the corpuscular radiation enters the atmosphere. Magnetic indices that predominantly reflect these events were obtained from the literature and correlated with the melatonin and conception data. Significant and inverse correlations were found for Inuit conceptions and the melatonin data. The correlations obtained for 48 contiguous states of the United States indicated that only the extreme northern states exhibited this relationship. These data were compared with a previous correlational study in the United States which established that sunshine was correlated with conceptions in the middle latitude and southern states. An hypothesis of dual control by electromagnetic and magnetic energies is proposed: melatonin is a progonadal hormone in humans controlled by both factors, depending on their relative strength. Other studies are reviewed regarding the possible factors involved in determining the annual pattern of human conceptions. Demographic studies of geographic variation in temporal patterns of conceptions, with particular regard to variations of the magnetic fields on the earth's surface, may provide some insight into the efficacy of these different factors.
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  • 4
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
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  • 5
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
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  • 6
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
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  • 7
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
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  • 8
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
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  • 9
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
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  • 10
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
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  • 11
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    Chromatographia 33 (1992), S. 103-112 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
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  • 12
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    Chromatographia 33 (1992), S. 177-185 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
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  • 13
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    Chromatographia 33 (1992), S. 218-224 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
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  • 14
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
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  • 15
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
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  • 16
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
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  • 17
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
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  • 18
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
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  • 19
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
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  • 20
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
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  • 21
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
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  • 22
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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  • 23
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    Chromatographia 33 (1992), S. 478-484 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
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  • 24
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
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  • 25
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    Chromatographia 34 (1992), S. 573-580 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
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  • 26
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
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  • 27
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    Chromatographia 34 (1992), S. 597-600 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
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  • 28
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
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  • 29
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
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  • 30
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
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  • 31
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
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  • 32
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    Chromatographia 34 (1992), S. 132-136 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
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  • 33
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    Chromatographia 34 (1992), S. 155-158 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
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  • 34
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
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    Topics: Chemistry and Pharmacology
    Notes: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
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  • 35
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    Chromatographia 34 (1992), S. 173-176 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
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  • 36
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    Chromatographia 34 (1992), S. 177-181 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
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    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
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  • 37
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    Chromatographia 34 (1992), S. 182-184 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
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    Topics: Chemistry and Pharmacology
    Notes: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
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  • 38
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    Chromatographia 34 (1992), S. 342-346 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
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    Topics: Chemistry and Pharmacology
    Notes: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
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  • 39
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
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  • 40
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
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    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
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  • 41
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
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    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
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  • 42
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
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    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
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  • 43
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    Chromatographia 34 (1992), S. 391-397 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
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    Topics: Chemistry and Pharmacology
    Notes: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
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  • 44
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    Chromatographia 34 (1992), S. 431-432 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
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    Topics: Chemistry and Pharmacology
    Notes: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
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  • 45
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
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    Topics: Chemistry and Pharmacology
    Notes: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
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  • 46
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
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    Topics: Chemistry and Pharmacology
    Notes: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
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  • 47
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
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    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
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  • 48
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
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    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
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  • 49
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    Chromatographia 34 (1992), S. 534-536 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
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    Topics: Chemistry and Pharmacology
    Notes: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
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  • 50
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    Chromatographia 29 (1990), S. 21-23 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Formaldehyde ; Reaction detector ; Polymer dispersions ; Nonwovens
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    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the determination of free formaldehyde in nonwovens in the presence of interfering components is described. After RP-HPLC separation the water extracted formaldehyde reacts with acetylacetone in a knitted open tube reactor to form a lutidine derivative which is measured, even at low concentrations, by the UV detector. The minimum detectable concentration is 25 μg/kg.
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  • 51
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Extraction cartridges ; Erythromycin ; Josamycin ; Serum and urine
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    Topics: Chemistry and Pharmacology
    Notes: Summary The re-usability of C18 solid-phase extraction (SPE) cartidges was assessed utilizing two different analytical procedures developed for the analysis of erythromycin and josamycin in human serum and urine. A statistical procedure using confidence intervals was employed in order to determine a 10% change in drug recovery on re-use with a 95% degree of certainty. The results obtained indicated that the SPE cartridges could be successfully re-used up to three times for serum and urine samples containing physiological concentrations of erythromycin base and propionate. However, in the case of josamycin, results were inconsistent after the second re-use of the extraction cartridges for serum samples. Reproducible results, however, were still obtained for urine samples using the same SPE cartridges up to four times. The results indicate that although succesful re-use of SPE cartridges is possible, each drug and associated extraction conditions need to be carefully assessed prior to implementing such re-use.
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  • 52
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    Chromatographia 29 (1990), S. 51-53 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrochemical detection ; Amino acid enantiomers ; OPA-TATG ; Fruit juices
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    Topics: Chemistry and Pharmacology
    Notes: Summary A fast and simple HPLC-method for the determination of synthetic amino acids in adulterated orange juice has been developed. The amino acid enantiomers were derivatized with a chiral reagent and the derivatives separated on a 3 μm particle size C18 column. An electrochemical detector operating in the oxidative mode was used for detection. The potential at which the derivatives are oxidized was determined by cyclic voltammetry. By using selective (electrochemical) detection it is possible to reduce the sample clean-up to simple centrifugation and filtration steps.
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  • 53
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed-functional silica ; Direct serum injection ; Drug analysis
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    Topics: Chemistry and Pharmacology
    Notes: Summary A new mixed-functional silica material has been developed for direct injection analysis of drugs in serum. The mixed-functional material is synthesized from porous silica by three steps; introduction of 3-glycidoxypropyl groups, introduction of phenyl groups, and hydrolysis of the oxirane ring to diol groups. The prepared column packing can be used for direct injection analysis of hydrophobic and hydrophilic drugs in serum over the eluent pH range employed for ordinary siloxane-bonded silica. The recovery of drugs from serum was almost 100%, regardless of the difference in their protein bindings.
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  • 54
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sample treatment ; Zone electrophoresis
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    Topics: Chemistry and Pharmacology
    Notes: Summary The design of a new valve arrangement for zone-electrophoretic sample treatment (ZEST) coupled online with high performance liquid chromatography is described. Characteristics of this valve, such as the internal heat development as a function of the current, have been investigated. By using quinidine and desipramine as model compounds it is shown that charged compounds can be isolated from biological samples, in about 15 min, with high selectivity. The carry-over of proteins to the analytical column has been compared with the carry-over using a pre-column sample clean-up method. The detection limits of quinidine and hydroquinidine (50 ng/ml), using zone-electrophoretic sample treatment coupled with column liquid chromatography, are in the same range as with direct injections using pre-columns.
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  • 55
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Factor analysis ; Experimental design ; Chemically bonded and silica phases ; Chalcones
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    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of a group of 38 E-s-cis and Z-s-cis chalcones on silica vs. nine polar chemically bonded phases is discussed. It was established that the relatively greatest similarity to silica is observed with the NH2, DIOL and CN phases, whereas the chargetransfer type phases and the NO2 one offer a different separation selectivity.
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  • 56
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    Chromatographia 29 (1990), S. 254-258 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line flame-AAS detection ; Hydraulic high pressure nebulization ; Trace metal speciation
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    Topics: Chemistry and Pharmacology
    Notes: Summary Hydraulic high pressure nebulization is used as an effective way of on-line coupling of HPLC to flame-AAS for speciation of metal compounds in the ng range. Compared to coupling with a conventional nebulizer a signal enhancement by a factor of 7.5 (peak height) and 10.1 (peak area) for copper is obtained. Using an injected volume of 50 μL the detection limits for Cu, Fe, Ni and Cd are below 0.1 μg/mL (=5ng) and for Mg below 0.01 μg/mL (=0.5ng). The effects of HPLC flow-rate and nebulization nozzle diameter on the signal peak height have been investigated. The performance of the system is demonstrated using speciation of iron. A base-line separation of Fe(II) and Fe(III) is achieved within two minutes. Also species changes (Fe acetate to Fe citrate) can be analysed using the proposed system.
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  • 57
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Kalman filter ; Cubic spline interpolation ; Al(III) and Cr(III)
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    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure for the simultaneous quantitation of Al(III) and Cr(III) ions by reversed-phase HPLC, after pre-column complexation with 8-hydroxyquinoline, is described. The deconvolution of the partially overlapped peaks was by the Kalman filter method which yielded accurate and precise results. Background removal from the chromatograms was by a new approach employing cubic splines as interpolators between the peak valleys. Finally, it is shown that the Kalman filter deconvolution, after subtraction of the background by cubic spline interpolation, allowed quantitation of Al(III) and Cr(III) down to 25 ppb for each metal. These concentrations were not detectable by conventional integration methods due to a very low signal-to-noise ratio.
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  • 58
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic parameter ; Capacity factor variation ; Organic modifier concentration ; Displacement model
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    Topics: Chemistry and Pharmacology
    Notes: Summary The dependence of the capacity factor (k′) on the concentration of the organic modifier (D) in the aqueous binary mobile phase in reversed-phase high-performance liquid chromatography has been investigated to evaluate the hydrophobicity of the solute molecule. The r-values, defined as the slope of log k′ vs. log(1/D) plots, were measured for various solutes and related to the non-polar surface area and the partition coefficients. The r-value was found to be a good indication of solute hydrophobicity. Detailed investigation of the results allowed to consider statistically the molecular posture of the solute adsorbed onto the stationary alkyl ligand.
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  • 59
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    Chromatographia 29 (1990), S. 419-428 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Acceptor-Donor complexes ; Selectivity enhancement ; Physical properties/retention correlation
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    Topics: Chemistry and Pharmacology
    Notes: Summary The paper describes the retention changes observed when an organic acceptor is added to the mobile phase of a liquid chromatography system. The capacity factor decrease depends on the donor character of the solute. Correlations with ionization potentials, HOMO energies and half wave oxidation potentials demonstrate the role of the organic acceptor. According monstrate the role of the organic acceptor. According to the chromatographic properties of the acceptor which is either unretained (TCNE) or slightly retained (TNF) different retention mechanisms are proposed.
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  • 60
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand exchange ; α-Amino-acids ; Racemate resolution
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    Topics: Chemistry and Pharmacology
    Notes: Summary Racemic α-alkyl-α-amino-acids are difficult solutes to resolve on chiral chromatographic phases derived from proline or pipecolic acid-polyacrylamide. The use of 3-carboxy-1,2,3,4-tetrahydroisoquinoline (porretine) as the chiral selector instead of the former α-amino-acids selectively resolves the α-alkyl-α-amino-acids.
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  • 61
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    Chromatographia 29 (1990), S. 482-488 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Binary gradient elution ; Optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A general procedure for optimizing binary gradient elution is described and applied to the specific separation of PTC-Amino Acid derivatives. The method requires two preliminary experimental runs under gradient elution mode followed by computer optimization. The different steps of the optimization procedure are described and the actual chromatograms are compared to the predicted ones.
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  • 62
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxygen free radicalsin vivo ; Spin traps ; Chemical traps ; Biological fluid and tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We describe here anin vivo method for direct and simultaneous determination and quantitation of the oxygen free radicals (OFR) superoxide (O2 −) and hydroxy (OH) radicals in biological tissue and blood of 2 week-old swine. Our method utilizes OFR trapping techniques, a spin trap 5,5-dimethyl-1-pyrroline-n-oxide (DMPO), 50 mg/kg, for O2 − and a chemical trap, Na salicylate, (SA, 100 mg/kg) for OH, was infused into the right atrium or pulmonary artery of two-week old swine (n=12). The OFR contents of coronary sinus (CS) blood and left ventricular (LV) tissue (quick frozen at 77°K) were measured by an HPLC method developed by us (Waters 590 solvent delivery system, using Waters electrochemical 460 EC detector, and 740 data module) at +0.6V. The DMPO-O2 − (measured as DMPO-OH) adduct assay was performed with a mobile phase consisting of 0.03 M citric acid, 0.05 M NaOH and 8.5% acetonitrile (Ph 5.1) at a flow rate of 1 ml/min through a Waters Resolve 5 μ C18 column. The salicylate-OH products (2,5 and 2,3 dihydroxy benzoic acids, DHBA) were assayed using mobile phase of 0.03 M Na citrate, 0.03 M Na acetate, with N2 bubbled (pH 3.6) at a flow rate of 0.8 ml/min through a 5μ Resolve C18 column. The detected peak for DMPO-O2 − adduct (9.5 min) was standardized with a hypoxanthine (HX) and xanthine oxidase (XO) mixture and the salicylate-OH products (11.5 min) were standardized with HX, XO and FeCl3. Forin vitro experiments, the blood/tissue samples were immediately (〈30 sec) incubated directly with 100 mM DMPO and/or 200 mM salicylate for 1 min, vortexed and injected for HPLC analysis. Superoxide dismutase (1 μM) and DMSO (10 mM) scavenged O2 − and OH adduct peaks by 77 and 80% respectively. The coefficient of variation for DMPO-O2 − adduct was ±12.6% and for salicylate-OH adduct was ±10.9% (n=12). The normal LV tissue levels determined for O2 − and OH were 0.41 and 0.32 nm/g wet weight, respectively. (In blood, the OFR contents were very small: 0.09 and 0.06 nm/ml, respectively.) This method is very specific and sensitive, 50 pm for O2 − and 0.2 pm for OH radicals.
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  • 63
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automation ; Column switching ; Serotonin in plasma ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, fast, fully automated method for plasma serotonin determination is described. Full automation is obtained by coupling two devices: a sample processing station and a solid-phase autosampler. The sample processing station dilutes the plasma sample and is then connected, on-stream, with the solid-phase autosampler. It firstly fills a loop with all the solvents necessary for the sample clean-up, then, inverting the flow, pumps these solvents through the silica-bonded cation-exchange disposable extraction cartridge positioned on the autosampler. For the elution, the cartridge is switched on-stream with the HPLC analytical column and serotonin is eluted by the HPLC mobile-phase. The HPLC separation is performed by ion-pairing reversed-phase liquid chromatography. The column effluent is completely reduced by an electrochemical reactor and serotonin is detected in an oxidation-mode by a dual-cell electrochemical detector. The plasma sample is 50 μl, the plasma sensitivity is 40 ng/l, the retention time is 6 min and the recovery is 95%. The repeatibility, the normal ranges for platelet-poor and for platelet-rich plasma have been established and correlation with manual HPLC calculated.
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  • 64
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cyclodextrins inclusion complexes ; Structure-retention relationships ; Polycyclic aromatics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of a group of polycyclic aromatic hydrocarbons having nearly equal ionization potentials but different molecular polarizability values was investigated using reversed-phase HPLC. Methanol-water binary systems containing β-cyclodextrin were applied as the mobile phase. The relationships between the capacity factors, molecular polarizabilities and the shape parameter of solute molecules are discussed.
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  • 65
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic Compounds ; Solvent extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The rate of extraction of phenolic compounds in two different solvents has been studied by liquid chromatography (HPLC) under reverse phase, gradient elution conditions. The solvents were diethyl ether and ethyl acetate. The method has been applied to two natural samples, a white wine and apple pulp.
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  • 66
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Charge transfer separations ; Hydrogenated polycyclic aromatics ; Coal liquefaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hydroaromatics (partially hydrogenated polycyclic aromatic hydrocarbons) generated in the course of the process play an important role in the catalytic hydroliquefaction of coal. A difficult analytical task is to identify and to quantify these hydroaromatics among the preponderant polycyclic aromatic hydrocarbons. Generally speaking, the method carried out uses the specific separation of hydroaromatic by charge transfer chromatography. Structural identification is effected by using gas chromatography, alone or coupled with mass spectrometry, and HPLC on amino bonded phase with UV detection. As an aid to obtaining the standard compounds that are essential in that work, this paper describes the application of the above analytical procedure to the catalytic hydrogenation products (RhCl3/NaBH4 and Pd/C) of benzo(a) and benzo(e)pyrenes.
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  • 67
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isoniazid metabolites in urine ; Fluorometric detection ; Post column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid, simple, and accurate method was developed for the determination of isoniazid and its metabolites (isonicotinic acid, acetylisoniazid and isonicotinylglycine) in urine by high-performance liquid chromatography. Urine is diluted with the mobile phase. After centrifugation, an aliquot of the supernatant is injected into the chromatograph. Isoniazid and its metabolites are separated by reversed-phase ionpairing chromatography with a mobile phase containing propanesulfonate and detected by fluorometry using postcolumn derivatization at high temperature (150°C) with hydrogen peroxide. The method was applied to the analysis of urine from patients receiving isoniazid therapy.
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  • 68
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cephalosporins ; Column switching in HPLC ; On-line plasma sample clean-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new high performance liquid chromatographic method was developed using a column-switching technique for the simultaneous determination of cephalexin, cefuroxime, cefoxitin and cephaloridine in plasma. The plasma samples were injected onto a precolumn packed with Corasil RP C18 (37–50 μm) after simple dilution with an internal standard solution in 0.01 M acetate buffer (pH 3.5). Polar plasma components were washed out using 0.01 M acetate buffer (pH 3.5). After valve switching, the concentrated drugs were desorbed in back-flush mode and separated on a Partisil ODS-3 column using acetonitrile in 0.02 M acetate buffer (pH 4.3) (15∶85, v/v) as the mobile phase. The method showed excellent precision with good sensitivity and speed with a detection limit of 0.5 μg/ml. The total analysis time per sample was less than 25 min, and the mean coefficients of variation for intra- and inter-assay were both less than 4.9 %. This method has been successfully applied to plasma from rats after subcutaneous injection of cefuroxime.
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  • 69
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Optimization of variables ; Information theory ; Kalman filter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The following chromatographic variables are totally optimized based on the recently developed information theory of optimization: mobile phase composition, column length, flow rate, wavelength, and the amount of internal standard. The optimal internal standard is selected from among six candidates. Two types of optimal conditions (Φ- and ϑ-optimals) are proposed: the Φ-optimal is defined as the most precise analysis (the maximal Φ) while the ϑ-optimal is the most efficient (rapid) analysis (the maximal ϑ). The observation times for the determination of an antipyretics mixture (three components) in liquid chromatography are ca. 50 s for the ϑ-optimal and ca. 8 min for the Φ-optimal. The reliability of the Φ- and ϑ-optimals is verified by experiments.
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  • 70
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    Chromatographia 30 (1990), S. 663-674 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; New stationary phases ; Peptides ; Performance testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Some new HPLC-phases (Polyencap, Hypercarb, Poly F, PRP∞) have been assessed for their suitability in the separation of peptides. Test criteria were peptide recovery, separation-efficiency, selectivity and stability. The eluents TFA/acetonitrile and acetatebuffer/propanol are compared. Of interest are the stability and recovery of Polyencap, the high separation efficiency of the standard RP-8 silica-based phase (Nucleosil C8) and the unusual peak-width of PRP∞. Acceptable conditions for peptide separations may be provided by Polyencap, but stability still has to be improved.
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  • 71
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    Chromatographia 30 (1990), S. 696-702 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ribosomal proteins ; Two-dimensional micro gel electrophresis ; Bacillus stearothermophilus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 50S subunits ofBacillus stearothermophilus ribosomes were isolated and crosslinked with the homobifunctional reagent diepoxybutane. Two protein-protein crosslinks consisting of the proteins L23-L29 and L3-L19 could be purified on a preparative scale using conventional column chromatography followed by a combination of different HPLC techniques. This procedure allows the isolation of the crosslinks in amounts high enough for the determination of the crosslinked amino acids.
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  • 72
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    Chromatographia 30 (1990), S. 298-300 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Binary liquid phases ; Molecular interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We apply our new retention model introduced elsewhere to the studies of intermolecular interactions between the solute and the remaining components of a normal-phase HPLC system using a binary mobile phase consisting of an alcohol and a hydrocarbon. This can be achieved through the analysis of the regressional parameters A, B, and C appearing in the relationship of solute retardation (RF) vs. mobile phase composition. Negative values of these parameters indicate a greater affinity of the solute to the stationary phase than to a given mobile phase moiety, whereas positive values have a reverse meaning. According to the absolute values of A, B, and C solute groups can be arranged according to the affinity toward a given mobile phase moiety, which is a detailed and important information regarding their separation, the stationary phase and with each individual constituent of the mobile phase.
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  • 73
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral interaction reagents ; Vitamin C ; D(−)-and L(+)-ascorbic acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC reversed-phase ion interaction reagent method is presented, which makes use of chiral compounds as the interaction reagents. By employing the optical isomeric forms of malic, tartaric and mandelic acids as the interaction reagents, a good separation of D(−) and L(+) ascorbic acid has been achieved. The method has also been applied to the identification of vitamin C in some medical formulations. The separation of te enantiomeric forms of DL malic acid has been attempted and a shor discussion is presented about the elution sequence in chromatographic separation of D- and L-enantiomers.
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  • 74
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Affinity chromatography ; Anhydrotrypsin ; C-terminal Arg- or Lys-containing peptides ; Diol silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Anhydrotrypsin (AHT), a catalytically inert derivative of trypsin in which the active site serine residue was converted to dehydroalanine residue by chemical modification, was immobilized onto diol silica through the activation with trifluoroethanesulfonyl chloride, and an AHT-diol-silica column was used for high-performance affinity chromatography separation of peptides containing arginine or lysine at their C-termini from the others. Improved separation in terms of speed was accomplished.
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  • 75
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mycotoxins ; Ochratoxin A ; Rumen fluid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An efficient procedure for the extraction and analysis of ochratoxins A, B, C and α from buffered rumen fluid has been developed. The samples have been cleaned up byliquid-liquid extraction and the separation of chratoxins was by isocratic elution on a 5μm C18 ODS-column which 0.083 M phosphoric acid/acetonitrile/isopropanol (55/35/10).
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  • 76
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Metal-interaction chromatography ; Rapid HPLC ; Phosphopeptides, proteins and peptides ; Micropellicular stationary phases ; Interaction of phosphate with Fe3+
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Short columns packed with micropellicular stationary phases consisting of 2-μm fused silica microspheres with covalently bound iminodiacetate (IDA) functions at the surface were used for rapid HPLC analysis of proteins by metal-interaction chromatography (MIC). In contrast to conventional porous stationary phases which elicit relatively long analysis times, the columns packed with sorbents having micropellicular configuration and Ni2+ or Co2+ chelated by the IDA functions yielded separation of model proteins in a few minutes with good resolution. A Fe3+/IDA column was used for separation of phosphorylated and non-phosphorylated peptides derived from enzymatically digested erythrocyte membrane proteins. Stability of the Fe3+/IDA column was quite satisfactory as determined by monitoring the iron content of the column effluent and by measuring the amount of iron present in the stationary phase.
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  • 77
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    Chromatographia 30 (1990), S. 421-423 
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Carbofuran ; Hydroponics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two analytical methods using GC/NPD and HPLC to analyse carbofuran in a nutrient solution used in hydroponic culture are described. Both methods show a high recovery, (greater than 90%), and their limits of detection are low.
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  • 78
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    Chromatographia 30 (1990), S. 428-431 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Immunoaffinity ; Modified acrylic copolymers ; Antibody anti-human serum albumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymer beads from acrylonitrile and ethyl either butyl acrylate or vinyl acetate, with amino, hydroxyl or carboxyl groups were activated with glutaraldehyde or water-soluble carbodiimide and coupled to human serum albumin. The obtained immunoadsorbents were applied to the isolation of anti-human albumin anibody from rabbit antiserum. Among the 22 studied copolymers only a few showed satisfactory effectiveness for immunoaffinity chromatography, similar to that noted for immunoadsorbents from commerical polymers.
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  • 79
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed-phase systems ; Octyl, octadecyl, phenyl and cyano-bonded phases ; Flavonoids ; Structure-retention relationships
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of an extended set of flavonoid compounds by octyl, octadecyl, phenyl and cyanopropyl-bonded, reversed-phase columns, with methanol, as the organic mobile phase modifier and acetic acid as the acid modifier is reported. Solvent strengths and useful ranges for both isocratic and gradient elution are determined. Relative retention is found to be independent of methanol volume fraction in the mobile phase for all the columns examined. Correlations between retention on different columns, specific selectivity effects and their dependence on molecular structure are analyzed. Practical applications for separation and identification are discussed.
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  • 80
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tandem mass spectrometry ; Peptides ; Loop valve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interfacing of a high performance liquid chromatograph, utilizing a dry-packed Spherisorb® C8 column (0.25×500 mm), with a four-sector tandem mass spectrometer via a frit-FAB probe is described. In order to utilize the sensitivity of the mass spectrometer, which is equipped with an array detector, the gradient solvent was split to a flow rate of 2–5 μL/min before the sample injector. The effluent flows directly into the mass spectrometer for the recording of the (M+H)+ ions of mixtures with the first of the two mass spectrometers (MS-1), or for their collision-induced-decomposition (CID) spectra by scanning the second mass spectrometer (MS-2). Those components that elute too close in time to allow the complete CID spectrum of each are diverted into a sample loop, which later can be switched in-line to the mass spectrometer to provide more time for collecting all the data. The method is demonstrated with a tryptic digest of the α-chain of human hemoglobin.
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  • 81
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    Chromatographia 33 (1992), S. 83-86 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-derivatization ; Catecholamines ; 9-fluorenylmethyl chloroformate (FMOC-Cl)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimum conditions for the separation of 9-fluorenylmethyl chloroformate derivatized catecholamines by HPLC are described; three catecholamines (noradrenaline, adrenaline and dopamine) and an internal standard (epinine) were separated in less than 20 minutes under isocratic conditions. This method is 17 to 350 times more sensitive than electrochemical detection, depending on the test compounds. It has been applied to the analysis of catecholamines in urine. The sample was extracted by a metal-loaded silica prior to separation.
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  • 82
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    Chromatographia 33 (1992), S. 567-570 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlorophylls ; Manganese(III) chlorophylls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Manganese chlorophylls have been synthesized by refluxing a mixture of pheophytins dissolved in acetone and manganese(II) acetate anhydride dissolved in glacial acetic acid. A good separation of manganese(III) chlorophylls has been attained by RP-HPLC using chemically bonded C18 silica as a stationary phase and methanol with 3% acetic acid as a mobile phase. An accurate and rapid HPLC method is described for the simultaneous determination of manganese(III) chlorophyll-a [Mn(III)-chl-a] and manganese(III) chlorophyll-b [Mn(III)-chl-b]. Tailing arising from dissociation of acetate ions is improved by addition of sodium acetate (5×10−3 M) to the mobile phase (acetone: methanol=90∶10, vol/vol). The analytical values obtained by the HPLC method are very close to the calculated contents in all samples, but those obtained by spectrophotometry are high because of the interferences from overlapping of absorption bands. In the proposed HPLC method the calibration graphs of Mn(III)-chl-a and Mn(III)-chl-b are linear in the concentration range 0–20 μg cm−3 with relative standard deviations (n=10) of 3.46% and 4.54%, respectively.
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  • 83
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 2′-Deoxyuridine ; Anomer separation ; Isomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic assay method was developed to separate 2′-deoxyuridine from its anomer and pentopyranosyl isomers. The influence of the pH of the mobile phase, the type of organic modifier and the column temperature on the chromatographic parameters was systematically investigated. Using a Hypersil C18 (5 μm) column at 10°C, the following mobile phase was found suitable: tetrahydrofuran −0.2 M potassium phosphate buffer pH 4.0-water (0.1∶5∶94.9, v/v).
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  • 84
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    Chromatographia 33 (1992), S. 122-126 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Controlled-porosity glasses ; Correlation between silica and porous glass ; Hydrocarbons separations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper deals with the use of controlled-porosity glasses (CPGs) as adsorbents for HPLC. The physicochemical and chromatographic properties of small-pore CPGs are compared to the analogous properties of silica gels. The results show good correlation between them and suggest the possibility of application of CPGs as adsorbents for liquid chromatography.
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  • 85
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Alpha 1-acid glycoprotein-bonded column ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantionselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propionyl,-butyrul and-valeryl PP) on an α1-acid glycoprotein (AGP)-bonded column have been investigated by changing eluent composition (eluent pH, buffer concentration, type and content of organic modifier). The retention of these cationic solutes, PP and its ester derivatives, was influenced by eluent pH, ionic strength and organic modifier content. The enantioselectivity was dependent on eluent pH and type of organic modifier. Reversal of the enantiomeric elution order of ester derivatives of PP (O-propionyl-butyryl) and-valeryl PP) occurred around eluent pH 6–7. These results suggst that chiral recognition or binding properties may be altered by the change in eluent composition, espeically eluent pH and type of organic modifier.
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  • 86
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Validation ; Aflatoxins in groundnut meal ; CB method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The efficiency of an analytical method for the determination of aflatoxins in groundnut meal has been statistically examined. The procedure consists of a phenyl bonded phase (PH) clean-up of an acetone: water (85∶15) extract followed by HPLC quantification. Average recoveries from spiked groundnut meal extracts were calculated to be 101.3% and 101.8%, with limits of detection of 7.4 and 2.62 μg/kg for aflatoxins-B1 and-B2 respectively. Higher recoveries of aflatoxin-B1 from naturally contaminated samples were recorded using the proposed procedure than those recorded using the official AOAC (CB) method although the precisions of the two methods were not found to differ at the 5% significance level. Similar recoveries of aflatoxin-B2 were recorded for both methods but the proposed procedure was found to be more precise. The proposed PH-HPLC method was far less time consuming and more economical on solvents than the CB procedure.
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  • 87
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
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  • 88
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV detection ; Pentafluorobenzyl chloride by UV detection ; Chloride in biological fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic method for the determination of chloride in plasma, urine, saliva, sweat and aqueous solution is described. Chloride, in solution in aqueous acetone, is converted by means of pentafluorobenzyl bromide into pentafluorobenzyl chloride. This derivative is separated on a ODS-5 μm reversed-phase column using isocratic elution with acctonitrile/water, 50/50, v/v, at a flow rate of 2.0 ml/min, and detected by a UV detector at 264 nm. The method is rapid, accurate and sufficiently sensitive for the determination of chloride in less than 10 μl sample volume of a biological fluid.
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  • 89
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    Chromatographia 33 (1992), S. 344-346 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Charge-transfer chromatography ; Carbon clusters ; Fullerenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparison of three binary mobile phases in LC separation of C60 and C70 fullerences on chemically bonded 2,4-dinitroanilinopropyl (DNAP) stationary phase was carried out, n-Hexane-benzene has been found to be the best mobile phase for efficient separation of the all-carbon molecules permitting high loads in preparative LC.
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  • 90
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    Chromatographia 33 (1992), S. 339-343 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Trichlormethiazide ; Electrochemical detection ; Diuretics in plasma and urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes a high-performance liquid chromatographic (HPLC) assay method for the determination of trichlormethiazide (TCM) in human plasma and urine. After extraction and separation on an ODS column TCM from plasma was detected by oxidation in an electrochemical detector (ECD) by a porous graphite electrode. The sensitivity was better than HPLC with UV detection, enabling the determination of 2 ng ml−1 TCM in human plasma. This method also allows determination of TCM at higher concentrations by exchanging the UV for the electrochemical detector. To study the pharmacokinetics, TCM in plasma and urine was assayed with coefficients of variation in the range 2–3%. The method has the advantages of high sensitivity for plasma assay and high precision with a simple procedure for both plasma and urine samples. Small samples of 0.5 ml plasma per assay also reduced the total volume of plasma needed.
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    Chromatographia 34 (1992), S. 31-34 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral mobile-phase additive ; Inductive adsorption ; Enantiomer resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of lactic acid enantiomers by inductive adsorption has been studied on silica columns using (S)-(+)mandelic acid as the chiral mobile-phase additive. The lactic acid peak is not very strongly retained, broad, strongly tailing and splits in two at loadings lower than 60 μmol cm−2 column cross-section and at mandelic acid concentrations higher than 10−4M. The splitting indicates partial separation of enantiomers: enantiomerically enriched fractions are obtained but not enantiomerically pure. Lactic acid retention strongly decreases with increasing concentration of both hydroxy-acids; mandelic acid acts by displacement and lactic acid acts by an overloading effect.
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  • 92
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diastereomer separation ; Chiral derivatizing agent ; Chiral oxazolidin-2-one
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic separation of racemic amines, carboxylic acids and alcohols can be achieved with excellent resolution as measured in terms of the chromatographic separation factor α by derivatization with a homochiral oxazolidin-2-one easily prepared in three steps fromendo-borneol. The resolved materials can be isolated in excellent yields by cleavage of the resultant diastereomers using conventional methods, which also allow recovery of the chiral resolving agent for re-use.
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  • 93
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Kalman filter ; Deconvolution ; Mycotoxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The potential of a computational approach for the quantitative resolution of seriously overlapping chromatographic peaks when there is loss of collinearity between the pure component peaks and the mixture peak has been explored. The program makes iterative use of the Kalman filter algorithm for resolving the mixture peak with the component peaks aligned according to some values of the position parameters, and of a steepest descent minimization procedure to find the optimal alignment. This combined procedure has been applied to the quantitive resolution of the HPLC chromatograms of alternariol and altenuisol mycotoxins in synthetic mixtures and in real samples.
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  • 94
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar mobile phase ; Direct injection of biological fluids ; Hexamethylene bisacetamide (HMBA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes the direct injection analysis of the anti-cancer drug hexamethylene bisacetamide (HMBA) in biological fluids by an HPLC column switching technique. The first chromatographic column, which provides for sample extraction and cleanup, employs a micellar mobile phase with SDS as the modifier. The second column, coupled on-line to the first, utilizes reversed-phase conditions for analysis. UV detection is employed at 210 nm. 282 samples from 12 cancer patients were analysed and good pharmacokinetics curves obtained. The drug gives recoveries of 94.0–100.9% with a relative standard deviation of 1.88%. A sample analysis is completed within 15 minutes. This method should be satisfactory not only for the analysis of HMBA but also, probably for other drugs in biological fluids.
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  • 95
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Suppressed ion chromatography ; Eluent composition and concentration ; Oxyanions in soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Methods based on simultaneous determination of oxy-anions in soil extracts are needed for studies of competitive adsorption of oxyanions by soils. We studied the effect of NaHCO3/Na2CO3 and NaOH/Na2CO3 concentrations on ion chromatographic (IC) determination of PO 4 3− , AsO 4 3− , SeO 4 2− , SeO 3 2− , WO 4 2− , and MoO 4 2− in a 10-mM NaCl matrix equilibrated with soils by using a Dionex 2002i IC unit. The eluent, 6.0 mM NaOH+4.5 mM Na2CO3, resolved the 10 mM Cl− from the six oxyanions. Elution times for Cl−, SeO 3 2− , SO 4 2− , NO 3 − , SeO 4 2− , PO 4 3− , WO 4 2− , MoO 4 2− , and AsO 4 3− were 1.7, 2.7, 5.2, 6.1, 7.8, 10.5, 14.3, 17.7, and 21.2, respectively. The recovery of 0.2-mM oxyanion standards added to the soil solutions ranged from 93.0 to 106.8%, with coefficients of variation ranging from 0 to 14.3%. The detection limits of the oxyanions studied ranged from 0.3 μM for SeO 3 2− to 9.0 μM for AsO 4 3− .
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  • 96
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column derivatization ; Light-scattering detection ; Carbohydrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of post-column fluorescence derivatization and evaporative light-scattering detection to analyse saccharides selectively by LC was investigated. In order to compare the performances of these two detection systems, factors such as reproducibility, detection limits and linear calibrations were determined. Despite the derivatization reaction step, post-column derivatization is superior from the standpoint of sensitivity. The detection of saccharides in beverages is also described.
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  • 97
    ISSN: 1612-1112
    Keywords: Gas chromatography — atomic emission spectroscopy ; Column liquid chromatography ; Metal chelate chromatography ; Diastereoisomer separation ; Vanadium complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Capillary gas chromatography with atomic emission detection (GC-AED), and high performance liquid chromatography (HPLC) have been employed to characterize isomerism of oxovanadium N,N'-propylenebis(trifluoroacetylacetoniminate). Other tetradentate Schiff base chelates of nickel, copper and palladium are also included in this study. Element-specific detection for metal and nonmetal elements in the chelates provides a means of identifying eluted peaks. Picogram detection limits for metals by GC-AED facilitated study of kinetic behavior at low concentration.
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  • 98
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carboxylic acids ; Fruit juices ; Wine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A direct method for the simultaneous determination of tartaric, malic, lactic, acetic, citric, shikimic, fumaric and succinic acids in fruit juices and wines by isocratic reversed phase HPLC is reported. The variables (pH, ionic strength, flow and temperature) have been optimized by a modification of the original simplex method. The separation factor (s) and calibrated resolution product (r*) have been used as criteria for selectivity optimization. After validation, the method has been applied to the determination of carboxylic acids in apple, orange and lemon juices, white and red wines and musts during the fermenation process.
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  • 99
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 29 (1990), S. 583-586 
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Intermolecular interactions ; Retention mechanisms in RP systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper we consider the possibility of gaining a better insight in the retetion mechanisms of solutes chromatographed in reversed-phase (RP) HPLC systems with the use of methanol-water binary mixtures as the mobile phase. This is done with help of the new retention model presented earlier as the relationship for the retardation coefficient (RF) of solute. The equation constants A, B and C were defined as proportional to the hypothetical retardation coefficients of the solute chromatographed separately in the three theoretically extracted moieties of the mobile phase (i.e. in pure methanol, pure water and the H-bonded associative methanol-water mixture); therefore the message imbedded in their numerical values can refer to the different and often opposite forces acting separately on the solute in a given RP-HPLC system from the side of each mobile phase moiety. An effort to decipher this message was undertaken upon the empirical results obtained for three groups of compounds, i.e., for dithia[3.3]phanes, and mono- and dihydroxyaromatics.
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  • 100
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ovomucoid-bonded silica ; Chiral separation ; Propranolol ; Propranolol ester derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention, enantioselectivity and enantiomeric elution order of racemic propranolol (PP) and its ester derivatives (O-acetyl,-propyl,-butyl and-valeryl PP) on an ovomucoid-bonded silica column have been investigated with respect to pH, ionic strength and organic modifier. For these cationic solutes, an increase in the organic modifier content and/or a decrease in the pH result in a decreased retention of both enantiomers. Enantioselectivity of the ester derivatives was higher than of underivated PP. The enantiomeric elution order was (S)/(R) for PP and (R)/(S) for the four ester derivatives, when ethanol or 2-propanol was used as the organic modifier. When methanol or acetonitrile was used as the organic modifier, inversion of the enantiomeric elution order was observed for O-valeryl PP with the use of methanol and for PP and O-propyl PP with acetonitrile. These results suggest that at least two chiral binding- or recognitionsites are present in a protein molecule and/or conformational changes occur in the chiral binding- or recognition-site(s) of the protein molecule bonded to a silica matrix.
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