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  • Column liquid chromatography  (495)
  • Springer  (495)
  • American Meteorological Society
  • 1990-1994  (495)
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  • 1
    Electronic Resource
    Electronic Resource
    Determination of intact molecular species of bovine milk 1,2-diacyl-sn-glycero-3-phosphocholine and 1,2-diacyl-sn-glycero-3-phosphoethanolamine by reversed phase HPLC, a multivariate optimization (1993)
    Springer
    Chromatographia 35 (1993), S. 517-523 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bovine milk ; Multivariate optimization ; Glycerophospholipids ; Molecular species separation ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The molecular species profile, representing the fatty acid combinations on the glycerol backbone, is the most fundamental description of an intact glycerophospholipid class and provides a key to understanding its functional characteristics. We have developed a powerful RP-HPLC method for the separation of molecular species, including so-called “critical pairs”, of natural mixtures of 1,2-diacyl-sn-glycero-3-phosphocholine 1,2-diacyl-sn-glycero-3-phosphoethanolamine from bovine milk and other natural sources. We have used a novel multivariate development and optimization strategy to locate the region of optimum separation conditions within a prechosen domain of the chromatographic parameter space.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267910
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and evaluation of cross-linked polyacrylate stationary phases for open tubular liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 597-606 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Open tubular columns ; Cross-linked polyacrylate stationary phase ; Photopolymerization ; Antracene derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polyacrylate films containing a lauryl moiety were fabricated on about 12 μm I.D. fused silica capillaries by in-situ photopolymerization of acrylates. Relatively thick films up to 1 μm were obtained by the technique. The films were tested as retentive layers for reversed phase open tubular liquid chromatography (OTLC). Due to the presence of the incorporated lauryl moiety in the layer considerable retention could be achieved for polar compounds with aqueous mobile phases. The efficiency of the prepared columns approximates to the theoretical value. The polyacrylate films appear to be extremely stable even under strong basic conditions. The films swell considerably in the presence of nonpolar solvents resulting in more favourable retention and a significant improvement of the chromatographic performance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267923
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  • 3
    Electronic Resource
    Electronic Resource
    Analysis of n-3 fatty acids in fish oils by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 627-630 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acid analysis ; Fish oils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chromatographic method has been developed for the determination of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in fish oil dietary supplements containing triglycerides rich in (n−3) polyunsaturated fatty acids (PUFAs). Following the ester saponification, free fatty acids were resolved by TLC into two fractions: i) a more mobile group of saturated and monounsaturated fatty acids and ii) a less mobile group containing PUFAs. The PUFA fraction was further analyzed by HPLC to determine the levels of EPA and DHA in the fish oil sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267927
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of carbidopa and levodopa in human plasma by high-performance liquid chromatography with electrochemical detection (1993)
    Springer
    Chromatographia 35 (1993), S. 607-612 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbidopa and levodopa in plasma ; Electrochemical detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A validated reversed-phase high-performance liquid chromatographic procedure employing electrochemical detection (LCEC) for the analysis of carbidopa and levodopa in human plasma is reported. The method is sensitive and specific with amperometric detection at a glassy carbon working electrode with Eapp=0.75 V vs. Ag/AgCl. The retention times of levodopa, internal standard, and carbidopa are 3.3, 4.5, and 9.7 minutes, respectively, with an overall chromatographic run time of 12.0 minutes. The peak height ratio versus plasma concentration is linear over the range of 5.0 to 500 ng/mL for each analyte and exhibits correlation coefficients of 0.9957 or better (n=9). The mean absolute recovery of carbidopa and levodopa using the described assay is 36.6 and 66.0%, respectively. The inter- and intra-day accuracy and precision are within 11.8% of the actual values for all concentrations. Also, due to the demonstrated instability of carbidopa and levodopa in plasma a procedure is provided to circumvent this. Blood collected in pre-treated Vacutainer tubes can be stored in an ice bath for up to 4 hours without any significant degradation, thereby providing a practical means for processing several clinical samples simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267924
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  • 5
    Electronic Resource
    Electronic Resource
    High-performance liquid chromatographic separation of fullerene mixtures using a novel stationary phase (1993)
    Springer
    Chromatographia 35 (1993), S. 631-636 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; FullereneSep® ; Separation factor ; HPLC-particle beam mass spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatographic separation of fullerene mixtures in the range C60 to C100 can be achieved using a novel stationary phase which rivals the performance of the more expensive ‘Pirkle-type’ columns currently employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267928
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  • 6
    Electronic Resource
    Electronic Resource
    Spurious interferences in the ion chromatographic determination of trace elements in human hair (1993)
    Springer
    Chromatographia 35 (1993), S. 675-678 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Trace metal determination ; Sample contamination ; Human hair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The dynamic ion-exchange chromatographic analysis of bivalent ions, such as Cu, Pb, Zn, Ni, Co and Mn in resistant organic matrices needs preliminary wet ashing with oxidizing acids (HNO3 and HClO4). Such treatment may lead to an increase in the amounts of metals present in the sample due to their release from containers or equipment used in an acidic environment and to metal impurities contained in the acids. The effect of these interferences in the determination of trace metals in human hair was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267936
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  • 7
    Electronic Resource
    Electronic Resource
    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. I. Chloro-added PAHs (1991)
    Springer
    Chromatographia 32 (1991), S. 334-340 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Cyanopropyldimethyl silica ; Chloro-added polycyclic aromatic hydrocarbons ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention characteristics in normal phase HPLC of highly biologically active chloro-added polycyclic aromatic hydrocarbons (PAHs) were studied. Silica, cyanopropyldimethylsilyl- and aminopropylsilyl- modified stationary phases were investigated. Retention properties of chloroadded PAHs on these phases were shown to be strongly influenced by the number of chloro-additions. This is due to the strong polarity of the methylene carbon at the chloro-addition site. Active silica had a strongly degrading effect on the unstable chloro-added PAHs during separation. Aminopropylsilica did not exhibit sufficient selectivity towards chloro-added PAHs when compared to chlorosubstituted PAHs. Cyanopropyldimethylsilica was shown to be applicable to a group separation of chloro-added and chloro-substituted PAHs. A fast clean-up procedure for chloro-added PAHs in complex samplesis outlined. It involves an initial elimination of more polar substances on a short open column with strongly deactivated silica and a subsequent separation on a cyanopropyldimethylsilyl HPLC column in normal phase mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321430
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  • 8
    Electronic Resource
    Electronic Resource
    Chromatography in pore networks II — The role of structure and adsorption in the band broadening (1991)
    Springer
    Chromatographia 32 (1991), S. 345-349 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column packings ; Pore size distribution ; Diffusion and adsorption ; Band broadening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The complex intraparticle structure typical of chromatographic column packings has been analyzed by use of an equivalent network model which emphasizes pore size distribution and connectivity. Special attention is given as to the way in which diffusion and adsorption interact and display modified peak spreading characteristics according to the morphology of the pore space. This study reveals a very significant increase in the column band broadening over that expected from physical adsorption which can arise from particular distributions of pore sizes. This has implications for designing packings which take advantage of the separating power due to adsorption but do not compromise the resolution of the chromatographic system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02321432
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  • 9
    Electronic Resource
    Electronic Resource
    Individual determination of ortho and non-ortho substituted polychlorobiphenyls (PCBs) in sediments by high performance liquid chromatographic pre-separation and gas chromatography/ECD detection (1993)
    Springer
    Chromatographia 36 (1993), S. 65-70 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; GC/ECD detection ; PCBs, ortho and non-ortho ; Chromatographic separation ; Congener determination ; FTIR identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure for the individual determination of ortho and non-ortho PCB congeners in sediments, using high performance liquid chromatography (HPLC) preseparation and gas chromatography/ECD detection, is described. Gas chromatography/FTIR spectrometry (GC/FTIR) and gas chromatography/mass spectrometry (GC/MS) were employed for individual congener identification and determination. Sample extraction, clean-up of extract and selective elution procedures were optimized by using reference certified marine sediment samples. Recovery and precision were typically 83% and 16% respectively at 2 ng/g of total PCB content. The proposed procedure, tested by analyzing real sediment samples, showed a reproducibility better than 20% at 13 ng/g PCB level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263839
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  • 10
    Electronic Resource
    Electronic Resource
    HPLC determination of pyroglutamic acid as a degradation product in parenteral amino acid formulations (1993)
    Springer
    Chromatographia 36 (1993), S. 75-78 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Glutamine ; Pyroglutamic acid ; Amino acids formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The aminoacid glutamine in aqueous solution and in conditions of high temperature and long term storage is partly transformed into pyroglutamic acid which exhibits potential neurotoxic effects. Commercially available aminoacid mixtures supplemented with glutamine are heat-sterilized and some losses of glutamine and formation of pyroglutamic acid may occur. The aim of the work was to set up an easy and reliable HPLC method which allows the determination of pyroglutamic acid as a degradation product of glutamine. The column was a 5 μm Hypersil ODS (100×4.6 mm) and the mobile phase 100% 0.007 M phosphate buffer pH 3.5. Stability studies in different conditions of temperature and time of storage were performed on aminoacid mixture available in the commerce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263841
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  • 11
    Electronic Resource
    Electronic Resource
    Determination of picomole amounts of carbonyls as luminarin hydrazones by high-performance liquid chromatography with fluorescence detection (1993)
    Springer
    Chromatographia 36 (1993), S. 96-104 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbonyl compounds ; Luminarin hydrazides ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Fluorogenic reagents (luminarin 3, luminarin 11 and luminarin 12), having a quinolizinocoumarin moiety as fluorophore and a carboxylic acid hydrazide function as reacting group, have been developed. These reagents were found to be highly sensitive fluorescence derivatization reagents for aldehydes and ketones in high-performance liquid chromatography. The reagents readily react with carbonyl compounds in aqueous sulphuric acid solution (0.1 M) at room temperature to produce the corresponding hydrazone derivatives, which can be separated on both reversed or normal-phase column. The structures of the derivatives were studied, together with their properties in reversed and normalphase chromatographic systems. UV absorbance, corrected fluorescence spectral data and quantum yields of luminarin 3, luminarin 11 and luminarin 12 are presented. The detection limits (signal to noise ratio=3) for aldehydes and ketones were in the sub-pmol range. Luminarin 3 was also applied to the determination of hydroxymethylfurfural (HMF) in orange juices and concentrates. The method for HMF involves the solid-liquid extraction of the juice by using a C-18 cartridge prior to derivatization and normal-phase separation of the derivative with fluorimetric detection at 387 nmex., 444 nm em. The calibration curve was linear for amounts of HMF ranging from 0.1 to 10 nmol. Intrarun relative standard deviation was 12.8% for 0.1 nmol and 2.6% for 1 nmol. Recovery studies indicated an average of 98.7±1.9% for juice concentrate and 99.8±3.2% for pasteurized juice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263844
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  • 12
    Electronic Resource
    Electronic Resource
    Chemometric optimization in drug analysis by HPLC: A critical evaluation of the quality criteria used in the analysis of drug purity (1993)
    Springer
    Chromatographia 36 (1993), S. 120-124 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Method development ; Chemometrics ; Response criteria ; Analysis of drug purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Optimization procedures require adequate response criteria to assess the quality of each chromatogram obtained during the process. The objective of this paper is to evaluate the possibility of using different resolution functions, in the chromatographic separation of a drug and its impurities (particularly the impurity just eluted after the drug). This study shows the limits of some resolution expressions. The interest of the simple Δt criterion, the difference between retention times, is presented in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263847
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of the organic modifier on the retention of retinoids in reversed-phase liquid chromatography (1993)
    Springer
    Chromatographia 36 (1993), S. 147-151 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polarity ; Retinoids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention of retinoids in reversed-phase liquid chromatography was studied using aqueous mobile phases of different composition (methanol 94–86% and acetonityrile 92–82%) at five temperatures (40–60 °C). With both organic modifiers the effect of the molecular structure increased as the water content and the polarity of the mobile phase increased. The temperature-dependence increased in the same manner with aqueous acetonitrile mobile phases. The π-π interactions between the retinoids and acetonitrile diminish when the water content of the mobile phase is increased, as happens also to the hydrophobic interactions with both organic modifiers. The net effect of these changes depends on the composition of the mobile phase. There was excellent correlation of retention with all polarity parameters studied(ϕ, P′, xe, xd, xn, E T N , δT, δ, δo and δd), when the calculations were made separately with methanol and acetonitrile. The volume fraction of the organic modifier, ϕ, was the only parameter describing the retention well in both organic modifiers simultaneously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263852
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  • 14
    Electronic Resource
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    Determination of a new calcium antagonist in human plasma by liquid extraction enrichment and HPLC with UV detection (1993)
    Springer
    Chromatographia 36 (1993), S. 343-346 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Aromatic amines ; Arylbenzylamide methylthioether derivative ; SL 85.1016 ; Pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method has been developed for the determination of SL 85.1016, a new calcium antagonist arylbenzylamide methylthioether derivative. SL 85.1016 and the internal standard, SL 87.0210, are extracted from alkaline human plasma withn-hexane and back extracted into 0.05 M phosphate buffer (pH 2.5; 0.2 ml). Acetonitrile (50 μl) is added to the final aqueous extract in order to prevent absorption of the compounds of interest onto the walls of the glass tube; this solution then is partially processed by HPLC on a C18 column with UV detection (254 nm). The determination limit of the method is 2 ng.ml−1 of SL 85.1016 in human plasma; the response to the drug is linear in the range 2–200 ng.mg−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263888
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  • 15
    Electronic Resource
    Electronic Resource
    Analysis ofAllium sulfur amino acids by HPLC after derivatization (1993)
    Springer
    Chromatographia 36 (1993), S. 347-350 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Allium ; Derivatization ; S-alk(en)yl-L-cysteine sulfoxides ; Sulfur amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two pre-column derivatization procedures coupled with reversed phase HPLC have been compared for the analysis ofS-Alk(en)yl0L-cysteine sulfoxides in variousAllium species. In order to establish external standards some (+/-) sulfoxides were synthesized, using a new method to enhance asymmetric synthesis of the diastereoisomers. The first derivatization method is the formation ofo-phthaldialdehyde/tert.-butylthiol derivatives which can be analyzed using UV detection. The second, presently used for amino acid analysis, is the Waters Pico-Tag method, which employs phenylisothiocyanate as derivatization reagent. As the Pico-Tag method was found to be the most efficient for determination ofS-alk(en)yl-L-cysteine sulfoxides it was used to determine the alliin content of various samples of garlic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263889
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  • 16
    Electronic Resource
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    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276844
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  • 17
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    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02276848
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  • 18
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    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02276845
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  • 19
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    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02276846
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  • 20
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    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276850
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  • 21
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    Collaborative study of the analysis of chlortetracycline by liquid chromatography on octylsilyl silica gel (1993)
    Springer
    Chromatographia 37 (1993), S. 640-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chlortetracycline ; Reversed-phase silical gel ; C8 bonded phase ; Collaborative study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An established method for the analysis of chlortetracycline by liquid chromatography using octylsilylated silica gel as the stationary phase was examined in a multicentre study involving five laboratories and a total of six columns. Three chlortetracycline hydrochloride samples were analysed. The main component and the impurities were determined. An analysis of variance, treating each column as a different laboratory, showed an absence of consistent between-laboratory bias and the presence of a significant laboratory-sample interaction. The repeatability and the reproducibility of the method, expressed as relative standard deviations of the result of the determination of chlortetracycline hydrochloride, were calculated to be 0.9% and 1.1% respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274116
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  • 22
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    Characterization of octadecylsilica stationary phases by spectroscopic methods (1993)
    Springer
    Chromatographia 37 (1993), S. 627-634 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; ODS phases ; NMR and FTIR characterization ; Stationary phase functionality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two spectroscopic methods, solid state NMR and diffuse reflectance FTIR, have been used in conjunction with liquid chromatographicretention data to identify and distinguish the functionality of octadecylsilica (ODS) stationary phases. NMR and FTIR spectra are indicative of various features of the different functionalities of the phases and this information can be used to elucidate the configuration of the organosilyl moiety in the ODS on the silica surface and explain why DSS phases have different molecular shape (mainly planarity) recognition capability.
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    URL: http://dx.doi.org/10.1007/BF02274114
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    Polypyrrole-coated silica as a new stationary phase for liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 423-428 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polymer-modified silica ; Polypyrrole cloride ; Polypyrrole dodecylsulfate ; Small molecules ; Polyaromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Polypyrrole chloride and polypyrrole dodecylsulfate coated-silica packing materials have been synthesized. Reverse-phase chromtographuy was employed to characterise both packings. A series of test compounds with known properties was used as molecular probes. They included benzene and derivatives, basic drugs, and polyaromatic hydrocarbons. A commericial C18 column was also used for the purpose of comparison in some cases.
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    URL: http://dx.doi.org/10.1007/BF02272259
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  • 24
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    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02262252
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    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02275893
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    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02275888
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    Enantiomeric resolution ofN-alkyl-N-methylanilineN-oxides by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 487-491 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiralcel OD ; N-Alkyl-N-methylanilineN-oxide enantiomers ; Chiral nitrogen centre ; Flavin-containing monooxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method for the resolution of the enantiomers of a series ofN-alkyl-N-methylanilineN-oxides is reported. The resolutions were achieved using a Chiralcel, OD chiral stationary-phase with a mobile-phase of hexane and ethanol in varying proportions. The chromatographic order of elution of the enantiomers ofN-ethyl-N-methylanilineN-oxide was determined to be (+)-(R) before (−)-(S).
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    URL: http://dx.doi.org/10.1007/BF02275784
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    Quantitative determination of sotolon in wines by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 539-542 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sotolon ; Vin jaune ; Flor-sherry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sotolon (4,5-dimethyl-3-hydroxy-2(5H)-furanone) is a key flavour compound in the french flor-sherry “Vin jaune”. This compound was determined quantitatively by extraction of 25 ml of wine on a XAD-4 resin, elution with diethyl ether, separation by HPLC on a Lichrospher 100 Diol column, elution with dichloromethane/hexane (60/40) and UV detection at 232 nm. The amount of sotolon in “Vin jaune” (120 to 268 μg/l) was related to the development of the yeast film over a period of 6 years. Only 6 to 51 μg/l were found in the “Vin de paille” which is made with overmaturated grapes of the same Savagnin vine-plant but without development of yeasts, and 80 to 140 μg/l in “Tokai” which are partly grown under a yeast film.
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    URL: http://dx.doi.org/10.1007/BF02275793
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    Determination of triamterene in urine by HPLC using fluorescence detection and column-switching (1994)
    Springer
    Chromatographia 38 (1994), S. 29-34 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching ; Determination of triamterene ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic method incorporating column-switching and fluorimetric detection for the determination of triamterene in untreated urine, is described. The urine samples (5 μL) were directly introduced onto an Hypersil ODS-C18, 30 μm (20 mm×2.1 mm I.D.) pre-column. Polar urinary compounds were removed by flushing the pre-column with water for 1 min, and the analyte was then switched onto an HP-LiChrospher RP C18,5 μm (125 mm×4mm ID) analytical column using an acetonitrile/phosphate buffer gradient elution. Fluorescence detection was performed at 230 nm excitation and 430 nm emission wavelengths. The recovery of drug was 102±2% in the 0.10–20.0 μg/mL concentration range, the limit of detection being 5 ng/mL. A validation of the usefulness of this procedure was accomplished by analysing urine extracts obtained from real samples.
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    URL: http://dx.doi.org/10.1007/BF02275723
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    Statistical evaluation of the validity of a method for characterizing stationary phases for reversed-phase liquid chromatography based on retention of homologous series (1994)
    Springer
    Chromatographia 38 (1994), S. 137-146 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Characterization of reversed phases ; Column hydrophobicity ; Column hydrophylicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The validity of a method for characterizing stationary phases for reversed-phase, liquid chromatography, based on the use of homologous series, has been evaluated. The method is based on a retention model which describes the dependence of the logarithm of the capacity factor on mobile phase composition and the carbon number of specific homologous series. A first-order as well as a second-order version of this model was investigated. The second-order model proved to be a significant improvement on the first-order model, even for smaller mobile-phase ranges. Nevertheless both models showed a significant lack of fit, reflecting the incompleteness of these models. Therefore, it is very questionable whether this method is suitable to describe HPLC-column characteristics like hydrophobicity and hydrophylicity.
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    URL: http://dx.doi.org/10.1007/BF02290326
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    Control of adsorption and solubility in gradient high performance liquid chromatography. Part 3. Sudden-transition gradient elution of styrene/ acrylonitrile copolymers (1994)
    Springer
    Chromatographia 38 (1994), S. 749-755 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/acrylonitrile) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and acrylonitrile could be separated according to composition by gradient elution through methanol after injection inton-heptane and sudden addition of 50, 60, or 70 vol% tetrahydrofuran. The peak sequence was the same as with a common binary gradientn-heptane/tetrahydrofuran, i.e., retention increased with acrylonitrile content of the samples. With copolymers containing 37, 31, or 26% acrylonitrile, the elution characteristics in the ternary systems could be logically extrapolated towards the points measured in the corresponding binary gradient system.
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    URL: http://dx.doi.org/10.1007/BF02269631
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    Chiral recognition of structurally related aminoalkylphosphonic acid derivatives on an acetylated beta-cyclodextrin bonded phase (1994)
    Springer
    Chromatographia 38 (1994), S. 771-775 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral recognition ; Aminoalkylphosphonic acid derivatives ; β-cyclodextrin bonded phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An acetylated β-cyclodextrin column was used to analyse the enantiomeric resolution of a number of aminophosphonic acids. Effects of the structure of these compounds on the extent of separation was examined. Molecular modelling studies were also carried out in an attempt to relate any interaction between the amino and phosphonic acid groups to chiral recognition by the stationary phase.
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    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
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    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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    URL: http://dx.doi.org/10.1007/BF02275902
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    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    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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    URL: http://dx.doi.org/10.1007/BF02276186
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    Interaction of cyclodextrins with drugs. Chromatographic investigation using a cyclodextrin bonded-phase and its application to chiral separations (1994)
    Springer
    Chromatographia 38 (1994), S. 381-385 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral separation ; Association constants ; Frontal analysis ; Cyclodextrin bonded-phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interaction between cyclodextrin and the drug (1R,2S,3S,4S)-(5Z)-7-(3-((phenylsulfonyl)amino)bicyclo[2.2.1]hept-2-yl)hept-5-enoic acid ((+)-S-145), was studied using α-, β-, and γ-cyclodextrin bonded-phase columns. Retention behavior of (+)-S-145 on these columns revealed that the strength of inclusion was β→γ→α-cyclodextrin. Interaction between β-cyclodextrin and (+)-S-145 was found to increase as the proportion of carboxylic ion in the (+)-S-145 molecule increased. Comparison of binding capacities of these bondedsilica gels obtained by frontal analysis and surface coverage indicated that availability of the immobilized β- and γ-cyclodextrin was 20–25%. The synthesized β-cyclodextrin bonded-phase column was superior to that of commercial columns in terms of chiral separation of (±)-S-145. A typical usage of the β-cyclodextrin column is discussed for separation of (±)-S-145 in plasma samples.
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    URL: http://dx.doi.org/10.1007/BF02269784
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    Reverse phase high-performance liquid chromatographic determination of primary and secondary aliphatic alcohols as phthalate monoesters by UV detection (1994)
    Springer
    Chromatographia 38 (1994), S. 417-420 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Primary and secondary aliphatic alcohols ; Aqueous derivatization ; Phthalic acid monoesters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Determination of primary and secondary aliphatic alcohols in aqueous and nonaqueous solutions by high-performance liquid chromatography (HPLC) is described. The alcohol is derivatized with phthalic anhydride to yield the corresponding monophthalate. Separation of the derivative is achieved on an ODS-10 reverse phase (RP) column by elution with an appropriate isocratic mobile phase of acetonitrile and aqueous phosphoric acid (0.1%). Detection is accomplished by UV absorption at 230 nm or 280 nm giving linear calibration plots, for alcohols in aqueous solution from 0.05% to 0.50% (w/v) and in pyridine solution from 0.0025% to 0.0250% (w/v).
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    URL: http://dx.doi.org/10.1007/BF02269829
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    Solute-micelle association constants of some polynuclear aromatic hydrocarbons by micellar liquid chromatography with alcohol additives to mobile phase (1994)
    Springer
    Chromatographia 38 (1994), S. 342-348 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hybrid mobile phases containing alcohols ; Solute-micelle association constants ; Polynuclear aromatic hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The interaction between some polynuclear aromatic hydrocarbons of environmental concern, and sodium dodecylsulphate and hexadecyltrimethylammonium bromide in the presence of methanol, 2-propanol and n-butanol has been evaluated by high-performance liquid chromatography using micellar mobile phases. Solute-micelle association constants have been determined for the compounds investigated. The results show that the addition of the alcohol to the mobile phase decreases the association constant values, methanol 〈2-propanol 〈n-butanol, relative to those in the absence of any additive.
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    URL: http://dx.doi.org/10.1007/BF02269778
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    Solid phase extraction applied to the determination of biogenic amines in wines by HPLC (1994)
    Springer
    Chromatographia 38 (1994), S. 571-578 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Biogenic amines ; Solid-phase extraction ; Derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method suitable for the determination of 19 biogenic amines in wine has been developed. The method involves derivatization of amines by treatment with dansyl chloride and solid-phase extraction of the derivatives. Prior to the derivatization procedure, clean-up of the wine sample with polyvinylpyrrolidone is carried out. Reversed-phase gradient elution HPLC with UV detection at 250 nm was used to determine these compounds. Some consideration was given to the effect of temperature on the separation process. Linearity of derivatization was obtained for amounts of all the biogenic amines ranging from 500 μg·L−1 to 20 mg·L−1. Limits of detection (signal-to-noise ratio=3) of the amines were similar for all the dansylderivatives (between 50 and 150 μg·L−1). Addition of standard amines was used for the determination of amine recoveries. These were better than 85% for ethanolamine, tryptamine, phenetylamine, putrescine, cadaverine and histamine. The overall process was succesfully applied to identify and quantify biogenic amines in white and red wines.
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    Enantiomer separaton of tifluadom and analogues by liquid chromatography with cellulose-based chiral stationary phases (1994)
    Springer
    Chromatographia 38 (1994), S. 629-632 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral/enantiomeric iseparation ; Cellulose-based chiral phases ; Tifluadom analogues ; 2-acylaminomethyl-1,4-benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolution of nine recamic mixtures of tifluadom analogues has been evaluated using the chiral stationary phases Chiralcel OD and Chiralcel OJ. The separation was performed on an analytical scale to optimize the conditions for chiral resolution, approaching baseline separation, of the two enantiomers. Eight racemates were baseline separated on Chiralcel OJ using a mobile phase of hexane/2-propanol.
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    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
    Details
    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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    Comparative study of solid-phase extraction of phenolic compounds. Influence of the ion pair reagent (1994)
    Springer
    Chromatographia 38 (1994), S. 579-584 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Ion-pair solid-phase extraction ; Comparison of sorbents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A comparative study of the solid phase extraction of phenolic compounds in water was carried out. Three different sorbents, C18, CH and PLRP-S, were tested for the preconcentration process in order to determine phenolic compounds in water at μg l−1 levels by reversed-phase LC separation and diode-array detection. The addition of an ion-pair reagent in the extraction process was also studied in order to increase the breakthrough volume of some compounds. Using the optimized conditions the limit of detection was less than 0.5 μg l−1, the maximum admissible concentration (MAC) in drinking water. The method was applied to determine phenolic compounds in Ebro river water however no phenols were found within the detection limits of the method.
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    Extraction of basic drugs from whole blood and determination by high performance liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 617-623 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Extraction-determination ; Basic drugs ; Blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the extraction of basic drugs from whole blood based on the use of a buffered protein precipitating reagent at pH9, to form NiWO4 in biological fluids and a ternary organic extracting phase of density below 1 is proposed. The extract is analysed by high performance liquid chromatography using a Hypersil C8 column and detection at 230 nm; the mobile phases used consist of binary mixtures of acetonitrile and aqueous solutions containing 20 mmol/l ofn-propylamine at pH 5 andn-hexylamine at pH 4, as blockers of the free silanol groups. The proposed method was applied to the determination of 16 basic drugs including narcotics, analgesics, cocaine-related compounds and adulterants, as well as 8 benzodiazepines, in whole blood.
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    Determination of imazethapyr and imazapyr residues in soil by coupled-column liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 62-66 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Imidazolinone herbicides in soil ; Imazethapyr ; Imazapyr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A column-switching method using two separation columns combined with UV detection at 260 or 236 nm has been used to determine the imidazolinone herbicides imazethapyr and imazapyr in soils. The residues were extracted from the soil with 0.1 M aqueous sodium carbonate solution and, after adjusting the pH to 2.0, the solution was partitioned with dichloromethane. Limits of determination for imazethapyr and imazapyr were 3 μg/kg. Recoveries were from 55 to 75% for both imidazolinone herbicides in the range 3–100 μg/kg in soil.
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    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
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    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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    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
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    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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    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
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    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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    A novel derivatisation procedure for inorganic mercury(II) for HPLC analysis (1994)
    Springer
    Chromatographia 39 (1994), S. 246-248 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mercury ; Diphenylethynylmercury
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new procedure for derivatisation of inorganic mercury(II) to diphenylethynylmercury with simultaneous extraction into dichloromethane is proposed. The organomercury derivative is effectively analysed by HPLC using UV detection. The calibration curve is linear over three orders of magnitude (0.02–50 mg L−1 Hg); the detection limit is 0.1 ng Hg. A preliminary study of the effect of potential interfering agents, in particular Cu(II), Zn(II), Cd(II), Pb(II), and cysteine, and applications of the present methodology to real environmental samples are presented.
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    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
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    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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    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
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    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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    URL: http://dx.doi.org/10.1007/BF02262326
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    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
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    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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    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
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    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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    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
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    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02262332
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    Correlation between retention in liquid chromatography and the adsorption energy (1992)
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    Chromatographia 33 (1992), S. 478-484 
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    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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    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
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    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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    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
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    Chromatographia 34 (1992), S. 573-580 
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    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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    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
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    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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    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
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    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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    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
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    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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    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
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    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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    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
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    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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    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Source: Springer Online Journal Archives 1860-2000
    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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    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
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    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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    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
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    Chromatographia 34 (1992), S. 155-158 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Source: Springer Online Journal Archives 1860-2000
    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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    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Source: Springer Online Journal Archives 1860-2000
    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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    Microcolumn liquid chromatography on carbon sorbents (1992)
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    Chromatographia 34 (1992), S. 173-176 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Source: Springer Online Journal Archives 1860-2000
    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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    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    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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    Silanol group effect in C18 bonded phases in HPLC (1992)
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    Chromatographia 34 (1992), S. 182-184 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Source: Springer Online Journal Archives 1860-2000
    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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    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    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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    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
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    Chromatographia 34 (1992), S. 347-356 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02268367
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    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02268371
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    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02268369
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    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02268372
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    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    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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    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02268379
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    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02290233
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    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Source: Springer Online Journal Archives 1860-2000
    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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    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Source: Springer Online Journal Archives 1860-2000
    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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    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02290247
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    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Source: Springer Online Journal Archives 1860-2000
    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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    URL: http://dx.doi.org/10.1007/BF02290248
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    A micro-scale method employing surface plasmon resonance detection for the determination of conditions for immunoaffinity chromatography of proteins (1993)
    Springer
    Chromatographia 35 (1993), S. 45-49 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Immunoaffinity chromatography ; Proteins ; Surface plasmon resonance detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The BIAcoreTM Biosensor System utilizes a detection principle known as Surface Plasmon Resonance (SPR) which, in simple terms, detects changes in the refractive index of a solution in contact with a gold film. The gold film is surface modified with carboxymethylated dextran to produce a hydrophillic matrix onto which macromolecules may be covalently immobilized. In this respect, the BIAcoreTM is similar to any other insoluble matrix, such as a chromatographic support. The SPR detection principle, however, allows one to directly ‘visualize’ the interaction under study, in real time and without the need for reporter molecules such as enzyme-labels. In addition, the very small sample requirements, automated robotics unit and ease of data analysis suggest the potential use of the BIAcoreTM instrumentation for assay development and possibly process development, especially where bio-specific interactions such as immunoaffinity chromatography are used as a step in the process. In this report, we demonstrate the use of the BIAcoreTM SPR detector for the micro-scale determination of conditions for immunoaffinity chromatography of soluble complementreceptor 1, sCR1.
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    Optimisation of post-column reaction detector for HPLC of explosives (1993)
    Springer
    Chromatographia 35 (1993), S. 5-12 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Post-column reaction detector ; Explosives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Improvements in selectivity and sensitivity in the analysis of common explosives, like nitrate esters, nitramines and nitroaromatic compounds can be achieved by post-column derivatisation in a two step reaction detector. The first step in derivatisation is the photolysis of the analytes with UV at 254 nm. The photo reactor consists of a crocheted 20 m Tefzel capillary, which is coiled around a low pressure mercury lamp. In second step the nitrite ion generated is subsequently detected by a colourimetric reaction. The azo dye formed can be selectively detected at 540 nm. Addition of alkali after chromatographic separation to prevent oxidation of initially formed nitrite to nitrate during photolysis leads to a complex multistage arrangement. However, the contribution to peak broadening by the reactor is negligible and it is possible to detect 25–50 ppb of nitramines and 30–100 ppb of nitrate esters. Another advantage of the method is the selective detection of nitro compounds, even in complex matrices. The trace analysis of explosives is of growing interest in forensic science as well as in environmental analysis. It has been shown [1] that explosives can easily be extracted from soil and debris by the use of supercritical carbon dioxide. The separation and determination of explosives by gas chromatography is hindered by their thermal instability. In HPLC only the nitro aromatic explosives can be detected with sufficient sensitivity. Other types of explosives like the esters of nitric acid or nitramines do not absorb sufficiently in the UV region for sensitive detection. It has been shown [2] that explosives are liable to photochemical decomposition in the UV region, resulting in nitrate and nitrite, which have been detected after separation by ion-pair chromatography with electrochemical detection. A more sensitive and selective detection of nitrite has been possible in flow injection analysis [3]. Here a modified Griess reaction has been used. In a first step nitrite ions are used to form the diazonium salt with sulfanilamide which is coupled in a second step with N-[naphthyl-(1)]-ethylene diamine (NED) to form a redviolet azo dye with an absorption maximum at 540 nm. The advantage of this method is selective detection in the visible region, where hardly any other organic components are detected, which might be present in a crude environmental sample. In this paper the transfer of the Griess reaction to post-column derivatisation in RP chromatography of explosives will be described, and the optimisation of trace analysis of these solutes will be discussed.
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    Optimizing separations in reversed-phase liquid chromatography by varying pH and solvent composition (1993)
    Springer
    Chromatographia 35 (1993), S. 18-32 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reverse phase ; Optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An interpretive optimization procedure in which pH can be one of the variables is presented with the emphasis on optimizing separations. When varying the pH in reversed-phase liquid chromatography the retention of ionogenic solutes will change. Thus, the selectivity between ionogenic and neutral solutes or between ionogenic solutes mutually can be optimized. However, pH also greatly affects the efficiency (plate count) and peak shape (asymmetry). Optimum selectivity (i.e. large differences in retention times) may be observed under conditions where peaks are broad and asymmetrical. Thus, it is essential to simultaneously consider retention, peak width and peak shape and their effects on separation (effective resolution) in pH-optimization studies. A procedure in which this is done is presented and applied to optimizing the separation of a synthetic mixture of selected pharmaceuticals. After initial experiments to establish the parameter space (boundaries for pH and binary methanol — water composition), twelve experiments are performed according to a 3×4 experimental design. At each loaction the retention, peak height, peak area and peak symmetry are recorded for each solute. These data are then used to build models for each of the four characteristics and for each solute. From this set of models the response surface, describing the quality of separation as a function of pH and composition, can be calculated. A variety of optimization criteria (quantifying quality of separation) can be used. The optimum corresponds to the highest point on the response surface.
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    Separation and identification of fullerenes by liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 38-44 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fullerenes ; On-line and off-line identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of fullerenes with a monomeric octadecylsilica bonded phase using n-hexane or toluene/methanol mobile phase systems is described. Analytical and preparative separations, incorporating on-line UV/VIS spectral measurements, confirmed the existence of large fullerenes such as C76, C78 and C84. However, isomers of C78 and C84 were not conclusively found.
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    HPLC determination of volatile phenols in wines (1993)
    Springer
    Chromatographia 35 (1993), S. 50-54 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Volatile phenols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An alternative to the traditional solvent extraction method used to extract and rapidly quantify ethyl-and vinylphenol and ethyl-and vinylgaiacol from wine is presented. The method is based on retention of volatile phenols on adsorbants. Among the tested resins, the most efficient, AG 2-X8 (anion exchange resin), worked as well with a synthetic solution as with wines. The percolation of clarified wine adjusted to pH 9 on this resin permits, in particular, the elimination of organic acids. Phenols are not eluted after rinsing the column with 1N HCl, but are eluted with methanol after this treatment. Good recovery (91 %) and good repeatability are observed. The eluate is directly analysed by HPLC on an RP18 column after two-fold dilution in water. The four volatile phenols were completely separated and detected by UV at 280 nm with high sensitivity (20–40 ppb). No interference with other compounds were noted in the different wines analysed.
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    Ion-pair LC of sugars at alkaline pH and pulsed electrochemical detection (1993)
    Springer
    Chromatographia 35 (1993), S. 61-66 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Ion-pair separation ; Pulsed electrochemical detection ; Hypercarb and PLRP-S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sugars, sugar acids, amino sugars and oligomers are separated as ion-pairs with hydrophobic counter ions at alkaline pH using PLRP-S and Hypercarb as solid phases. Important parameters for regulation of retention and selectivity are nature and concentration of the counter ion, pH (hydroxide concentration) and temperature. Reversals in the elution order wer obtained in some cases. Oligosaccharides are highly retained in these systems. The addition of organic modifiers to the mobile phase for elution of the solutes were found to interfere with the pulsed electrochemical detection (PED). Anions added to the mobile phase compete with the solutes for ion-pair retention, hence, decreasing the capacity factors, and phosphate could be used for this purpose in the separation of maltooligomers (M2-M10) from corn syrup.
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    Ion-pair LC of carbohydrates at alkaline pH. Separation and retention behaviour of glycoconjugates (1993)
    Springer
    Chromatographia 35 (1993), S. 55-60 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Ion-pair separation ; Glycoconjugates ; PRP-1 and PLRP-S
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new technique for the separation of carbohydrates as ion-pairs in strongly alkaline solution is presented. Carbohydrates are weakly acidic and partly present as anions at pH≥12 [1]. They are retained as ion-pairs on polymeric solid phases (PRP-1 and PLRP-S) with a hydrophobic quaternary ammonium counter ion present in the mobile phase. The effects of nature and concentration of mobile phase components on the retention of carbohydrates have been investigated and an ion-pair distribution model is proposed. The influence of temperature indicated no changes in retention mechanism with high counter ion concentration, but the resolution decreased with increasing temperature. Saccharides added to the mobile phase were shown to increase the retention and the selectivity.
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    The glycan patterns at the individual glycosylation sites in orosomucoid from allergic reaction patients (1993)
    Springer
    Chromatographia 35 (1993), S. 90-92 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1-acid glycoprotein ; Complex glycans ; Allergic reaction ; Terfenadine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Little is known about the alterations that have occurred at the individual glycosylation sites in allergy patients or how these glycosylation patterns may change after anti-allergy treatments. Using reverse-phase HPLC, we have quantitated the glycoforms present at the individual glycosylation sites on orosomucoid isolated from the sera of allergic reaction patients and an allergic reaction patient treated with the antihistamine Terfenadine. The glycan structures isolated from the five glycosylation sites for the individual taking Terfenadine were all within normal ranges. It is suggested that if the changes in glycosylation in OMD in the allergic state are functionally driven, then it should be possible to correlate biological activities with quantitative changes at the individual glycosylation sites, and hence further define the role of OMD in allergy and inflammation.
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    A comparison of temperature and mobile phase composition effects for bonded liquid crystal and polymeric stationary phases in HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 85-89 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Bonded liquid crystals ; Polymeric stationary phases ; Variable temperature studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using two polycyclyic aromatic hydrocarbons as solutes, a comparison is made between a bonded liquid crystal stationary phase and a conventional polymeric C-18 phase. The bonded nematic liquid crystal phase was the silanized form of 4-[4-(allyloxy)benzoyl-oxy]biphenyl and the polymeric phase was Vydac 201TP. Both phases display shape and planarity selectivity as indicated by the results of the variable temperature and mobile phase composition studies. The slot theory of retention can be used to explain these results. However, the liquid crystal phase is more sensitive to molecular geometry, probably due to its more ordered structure on the surface. Variable temperature experiments which compare retention during both heating and cooling provides additional support for this conclusion. With the polymeric bonded C-18 phase, each solute had identical retention at the same temperature during both the heating and cooling cycles. On the bonded liquid crystal phase, measurable differences in retention were observed at identical temperatures depending on whether the column was heated or cooled. This effect is attributed to a degree of partially reversible disordering which occurs as the column temperature was increased. However, conditioning with the appropriate mobile phase can restore the original retention characteristics of the bonded liquid crystal phase.
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    Chromatographic comparison of the relative Lewis acidities of alumina and zirconia (1993)
    Springer
    Chromatographia 35 (1993), S. 133-138 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ligand exchange chromatography ; Zirconium oxide ; Aluminum oxide ; Lewis acids and bases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic properties of alumina and zirconia are compared with respect to their relative Lewis acidities when parabenzoic acid derivatives are chromatographed in aqueous media. Weak Bronsted acids show similar capacity factors on alumina and zirconia. As solute Bronsted acidity increases, the capacity factor increases more significantly on the zirconia phase than on the alumina phase. Efficiencies, as determined by the dominant desorption rate constants, are generally comparable between the two phases with alumina showing slightly higher efficiencies, Secondary interactions between the solutes and the stationary phases are nearly absent on zirconia but are very apparent on the alumina phase.
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    Development and comparison of different fluorimetric HPLC-methods with standard methods for the determination of formaldehyde in the atmosphere (1993)
    Springer
    Chromatographia 35 (1993), S. 142-148 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Formaldehyde in air ; Fluorimetric detection ; Comparison of fluorescent derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Three different fluorimetric methods for the measurement of atmospheric formaldehyde are described. The relatively unknown 2-diphenylacetylindan-1,3-dionhydrazine (DAIH) method was developed and optimized with an improved limit of detection of 2 ppbv corresponding to a sample volume of 7.5 L. Separation of lutidines necessary for the Nash method was successfully carried out and the separation time was reduced by a factor of 5. The detection limit of the Nash method was improved to 1 ppbv. In comparison, the N,N-diphenyl-1-naphthylamine-5-sulfonhydrazine (DNSH) method performed in a similar manner, reached an LOD of 0.5 ppbv. Finally, measurements made in candle smoke using the three different fluorimetric methods and three standard methods yielded very similar results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269693
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  • 91
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    HPLC determination of 18 β-glycyrrhetinic and glycyrrhizinic acids in toothpastes after solid phase extraction (1993)
    Springer
    Chromatographia 35 (1993), S. 167-172 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 18 β-glycyrrhetinic acid ; Glycyrrhizinic acid ; Toothpastes ; Solid phase extraction (SPE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary HPLC methods suitable for the selective and sensitive determination of 18 β-Glycyrrhetinic acid (GT) and Glycyrrhizinic acid (GZ) in toothpastes have been developed. The methods involve a preliminary quantitative solid phase extraction (C-18 sorbent) for sample clean-up and analyte concentration. Chromatographic separations were performed on reversed phase (C-8; C-18) columns using mixtures of methanol and phosphate buffers (pH 3.0) as the mobile phase under isocratic or gradient elution conditions. The method were applied successfully to the analysis of commercial toothpastes containing low levels (0.013–0.065%) of GT and GZ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269697
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  • 92
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    Direct enantiomeric analysis of amphetamine in plasma by simultaneous solid phase extraction and chiral derivatization (1993)
    Springer
    Chromatographia 35 (1993), S. 153-159 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amphetamine in plasma ; Enantiomeric separation ; Solid phase derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical approach has been developed for the one step determination of enantiomeric amphetamine composition in plasma, using on-line, pre-column solid phase derivatization with reversed phase HPLC separation. The high molecular weight protein components were excluded by the small pore structure of the polymer and washed out of the reaction column before derivatization. Spiked amphetamine in human plasma was extracted and derivatized by the polystyrene based FMOC-L-prolyl solid phase reagent. The derivatized diastereomers were separated on a conventional ODS column with an ACN/H2O mobile phase. No kinetic resolution or racemization was observed in this solid phase derivatization. Calibration plots and reproducibility experiments were performed to demonstrate the validity of the new approach. Automation of the procedure provided a simple and reproducible method for direct chiral recognition in plasma samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269695
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  • 93
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    Determination of trace amounts of morpholine and its thermal degradation products in boiler water by HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 173-176 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Pre-column derivatisation ; Morpholine and degradation products ; Boiler feed water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Morpholine and its amine-type thermal degradation products present in boiler feed water and steam condensate were derivatised with N-succinimidyl-p-nitrophenylacetate. These pre-column derivatives were determined by high-performance liquid chromatography with UV detection at 280 nm. The analytical column was Supelco-sil-ODS with an isocratic mobile phase. Morpholine and its breakdown products were monitored in the range 0.01–10 μg ml−1 with a relative standard deviation of 0.4–3.0%. Chromatographic analysis of boiler feed water and steam condensate samples collected from a boiler servicing a petroleum refinery is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269698
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  • 94
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    An improved HPLC system for the analysis of photosynthetic pigments (1993)
    Springer
    Chromatographia 35 (1993), S. 189-192 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carotenoid pigments ; Chlorophylls ; Photosynthestic tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatography system for the analysis of photosynthetic pigments is presented. The method employs an octadecylsilica stationary phase, a programmed quaternary mobile phase consisting of mixtures of methanol, acetonitrile, water and hexane, and a photodiode array detector. Carotenoids and chlorophylls are rapidly analysed in a single chromatographic separation. Thecis-trans isomers of most carotenoids are separated by this method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269701
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  • 95
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    Determination of monensins A and B in the fermentation broth ofStreptomyces cinnamonensis by high performance liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 206-208 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Monensins A and B ; Fermentation broth ; Streptomyces cinnamonensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High performance liquid chromatography on an octadecyl silica column has been used to determine both the monensin A: monensin B ratio and by the method of standard addition, the concentration of both in the fermentation broth ofStreptomyces cinnamonensis. Refractive index detection was preferred to ultraviolet owing to the presence of UV-absorbing components which could not be completely separated from the substances of interest. A linear relationship was obtained from the calibration data. The coefficients of variation for the estimation both of the ratio and the concentrations of the compounds were better then 5%. The estimated limit of detection for both substances was about 1 μg/ml. The results obtained from the determination of the ratios of monensins were compared with those obtained by chemical ionization mass spectrometry. Chromatographic separation of monensins on the silica gel column is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269704
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  • 96
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    HPLC determination of antioxidant synergists and ascorbic acid in some fatty pharmaceuticals, cosmetics and food (1993)
    Springer
    Chromatographia 35 (1993), S. 232-236 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ascorbic acid ; Antioxidant synergists ; Food, pharmaceuticals and cosmetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A specific and sensitive reverse-phase HPLC method for the quantitative determination of ascorbic acid and antioxidant synergists (1-tartaric acid, citric acid, lactic acid as lithium lactate and EDTA) in fatty pharmaceuticals, cosmetics and food has been developed. Two extraction procedures were used; treatment with hot water, and extraction with water from a hexane dilution of the product. No significant differences between the two procedures were found (p〈0.05), except for ascorbic acid. Quantitative determinations were performed using a C-18 column and sulfuric acid (pH 1.95) mobile phase. With detection, at 210 nm, lactic acid overlapped with ascorbic acid, but the former could be readily identified by TLC. Ascorbic acid was detected at 254 nm, when lactic acid (as lithium lactate) did not interfere in the analysis. Mean recoveries for tartaric, citric and lactic acids were in the range 96–101%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269708
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  • 97
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    A study of the use of microdialysis probes as a sampling unit in on-line bioprocess monitoring in conjunction with column liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 285-289 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microdialysis ; Fermentation monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automated on-line sampling and analytical set-up for the control of fermentations was studied incorporating a microdialysis probe as the sampling device. Applications to a penicillin broth and an ethanol fermentation were studied. Typical recovery values of carbohydrates were found to be close to 100% even after exposure of the microdialysis probe in the process for about 30 h.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277511
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  • 98
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    The on-line determination of the enantiomeric purity of enzymatically produced chiral compounds (1993)
    Springer
    Chromatographia 35 (1993), S. 264-268 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomer separation ; Stereospecific synthesis ; Crown ether phase ; Immobilized enzyme reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A prototype of a coupled-column chromatographic system has been developed to determine the enantiomeric purity of enzymatically produced chiral compounds. In this system, an immobilized enzyme HPLC reactor based upon α-chymotrypsin (ACHT-IMER) was linked through a switching valve to a chromatographic column containing a crown ether-based chiral stationary phase (CR-CSP). Although ACHT is normally stereospecific for the L-enantiomorphs of aromatic amino acids, L-tryptophan (L-TRP), L-tyrosine and L-phenylalanine, we were able to achieve the hydrolysis of D-TRP methyl and ethyl esters on the ACHT-IMER. The percent of hydrolysis of the D-TRP esters could be manipulated by varying the resident time in the ACHT-IMER. In a series of experiments, D,L-TRP methyl or ethyl esters were injected into the ACHT-IMER, the flow stopped and after resuming the flow, the eluent which contained the hydrolyzed aminoacids, D- and L-TRP, was switched onto the CR-CSP where the enantiomeric composition of the TRP peak was determined. This configuration is a model for other IMER/CSP coupled-column systems which can be used for analytical and preparative applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277507
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  • 99
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    Determination of the lipophilicity of some anti-hypoxia drugs: Comparison of TLC and HPLC methods (1993)
    Springer
    Chromatographia 35 (1993), S. 275-280 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Anti-hypoxia drugs ; Lipophilic character and retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The lipophilicity of 14 anti-hypoxia drugs has been determined by reversed phase thin-layer (RPTLC) and reversed phase high performance liquid chromatography (RPHPLC) in eluent systems containing different concentrations of acetonitrile and potassium dihydrogen phosphate. There was significant correlation between lipophilicity and the specific hydrophobic surface area of the drugs in RPTLC, indicating that the drugs behave as an homologous series of compounds. In RPTLC the concentration of buffer has a negligible effect on the retention of the drugs whereas in RPHPLC the buffer concentration influenced the retention. This discrepancy can be explained by the lower sensitivity of RPTLC. There was strong correlation between lipophilicity values determined by both methods, proving that both are suitable for the determination of molecular lipophilicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277509
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  • 100
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    Enantiomeric separation of close analogs to naturally occurring 1,4-benzoxazin-3-ones by liquid chromatography using β-cyclodextrin-modified stationary phase (1993)
    Springer
    Chromatographia 35 (1993), S. 302-304 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; 1,4-Benzoxazin-3-ones ; Cyclic hydroxamic acids ; β-Cyclodextrin modified silica gel ; Enantiomer separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A liquid chromatographic procedure on a 5 μm LiChroCART column using chemically bonded β-cyclodextrin (ChiraDex) as chiral selector was developed for the enantiomeric separation of four 2H-1,4-benzoxazin-3(4H)-ones which are close analogs of the cyclic hydroxamic acids 2,4-dihydroxy-2H-1,4-benzoxazin-3(4H)-one (DIBOA) and 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3 (4H)-one (DIMBOA) naturally occurring inGramineae species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02277514
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