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  • Column liquid chromatography  (1.216)
  • Springer  (1.216)
  • American Chemical Society
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  • 101
    Digitale Medien
    Digitale Medien
    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275888
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  • 102
    Digitale Medien
    Digitale Medien
    Enantiomeric resolution ofN-alkyl-N-methylanilineN-oxides by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 487-491 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiralcel OD ; N-Alkyl-N-methylanilineN-oxide enantiomers ; Chiral nitrogen centre ; Flavin-containing monooxygenase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275784
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  • 103
    Digitale Medien
    Digitale Medien
    Quantitative determination of sotolon in wines by high-performance liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 539-542 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sotolon ; Vin jaune ; Flor-sherry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275793
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  • 104
    Digitale Medien
    Digitale Medien
    Determination of triamterene in urine by HPLC using fluorescence detection and column-switching (1994)
    Springer
    Chromatographia 38 (1994), S. 29-34 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Column-switching ; Determination of triamterene ; Fluorescence detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275723
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  • 105
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Characterization of reversed phases ; Column hydrophobicity ; Column hydrophylicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290326
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  • 106
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Copoly(styrene/acrylonitrile) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269631
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  • 107
    Digitale Medien
    Digitale Medien
    Chiral recognition of structurally related aminoalkylphosphonic acid derivatives on an acetylated beta-cyclodextrin bonded phase (1994)
    Springer
    Chromatographia 38 (1994), S. 771-775 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chiral recognition ; Aminoalkylphosphonic acid derivatives ; β-cyclodextrin bonded phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269635
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  • 108
    Digitale Medien
    Digitale Medien
    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275902
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  • 109
    Digitale Medien
    Digitale Medien
    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276186
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  • 110
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Chiral separation ; Association constants ; Frontal analysis ; Cyclodextrin bonded-phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269784
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  • 111
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Primary and secondary aliphatic alcohols ; Aqueous derivatization ; Phthalic acid monoesters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269829
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  • 112
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Hybrid mobile phases containing alcohols ; Solute-micelle association constants ; Polynuclear aromatic hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269778
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  • 113
    Digitale Medien
    Digitale Medien
    Solid phase extraction applied to the determination of biogenic amines in wines by HPLC (1994)
    Springer
    Chromatographia 38 (1994), S. 571-578 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Wine ; Biogenic amines ; Solid-phase extraction ; Derivatization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277156
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  • 114
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Chiral/enantiomeric iseparation ; Cellulose-based chiral phases ; Tifluadom analogues ; 2-acylaminomethyl-1,4-benzodiazepines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277166
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  • 115
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275911
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  • 116
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Phenolic compounds ; Ion-pair solid-phase extraction ; Comparison of sorbents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277157
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  • 117
    Digitale Medien
    Digitale Medien
    Extraction of basic drugs from whole blood and determination by high performance liquid chromatography (1994)
    Springer
    Chromatographia 38 (1994), S. 617-623 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Extraction-determination ; Basic drugs ; Blood
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277164
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  • 118
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Column switching ; Imidazolinone herbicides in soil ; Imazethapyr ; Imazapyr
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02320459
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  • 119
    Digitale Medien
    Digitale Medien
    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275918
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  • 120
    Digitale Medien
    Digitale Medien
    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275921
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  • 121
    Digitale Medien
    Digitale Medien
    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275919
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  • 122
    Digitale Medien
    Digitale Medien
    A novel derivatisation procedure for inorganic mercury(II) for HPLC analysis (1994)
    Springer
    Chromatographia 39 (1994), S. 246-248 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Mercury ; Diphenylethynylmercury
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274507
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  • 123
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262320
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  • 124
    Digitale Medien
    Digitale Medien
    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262326
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  • 125
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262327
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  • 126
    Digitale Medien
    Digitale Medien
    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262330
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  • 127
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262332
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  • 128
    Digitale Medien
    Digitale Medien
    Correlation between retention in liquid chromatography and the adsorption energy (1992)
    Springer
    Chromatographia 33 (1992), S. 478-484 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262331
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  • 129
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269864
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  • 130
    Digitale Medien
    Digitale Medien
    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
    Springer
    Chromatographia 34 (1992), S. 573-580 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269866
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  • 131
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269867
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  • 132
    Digitale Medien
    Digitale Medien
    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269869
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  • 133
    Digitale Medien
    Digitale Medien
    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269873
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  • 134
    Digitale Medien
    Digitale Medien
    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 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269875
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  • 135
    Digitale Medien
    Digitale Medien
    Oxidation of acetophenone in a high temperature open-tubular capillary column liquid chromatographic system (1995)
    Springer
    Chromatographia 40 (1995), S. 99-101 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; High temperature open-tubular columns ; Solvent make-up ; Acetophenone oxidation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Acetophnone, a substance stable at room temperature, is readily oxidizes in a high temperature open tubular liquid chromatographic system by the residual oxygen in the mobile phase. The oxidation product is less UV absorptive and detection sensitivity decreases greatly. To prevent the oxidation, through degassing of the mobile phase is necessary.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274615
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  • 136
    Digitale Medien
    Digitale Medien
    The removal of endotoxins from protein solutions using column packings with aminated poly (γ-methyl L-glutamate) spheres (1995)
    Springer
    Chromatographia 40 (1995), S. 33-38 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Endotoxins ; Lipopolysaccharide ; Aminated poly(γ-methyl L-glutamate) ; Bovine serum albumin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method is described for the selective removal of endotoxins from various protein solutions using columns packed with aminated poly (γ-methyl L-glutamate) (PMLG-NH2) spheres. The PMLG-NH2 adsorbents showed a high adsorbing activity for endotoxins which had an ionic strength of μ=0.05–1.0 and pH 5.0–9.0. The endotoxin-adsorbing capacity per millitre of the wet adsorbent increased from 0.40 to 1.35 mg (E. coli O111: B4 LPS) at μ=0.2 and pH 7.0 while the aminogroup content of the adsorbent increased from 0.8 to 3.5 meq g−1. The PMLG-NH2-3.5 has an amino-group content of 3.5 meq g−1. This column packing selectively adsorbed endotoxins, without loss of the protein, from a γ-globulin or cytochromec solution which contained endotoxins at μ=0.05 and pH 7.0. On the other hand, when bovine serum albumin (BSA) was present in solution with endotoxins, both the endotoxins and the BSA were adsorbed by the column. The BSA-adsorbing activity increased with increasing amino-group content of the adsorbent. However, this undesirable adsorption was suppressed with increasing ionic strength of the buffer. As a result, when the packing which had an amino-group content of 1.5 meg g−1 was used in conditions of μ=0.2 and pH 7.0, the endotoxins were removed from a BSA-containing solution without affecting the recovery of the BSA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274604
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  • 137
    Digitale Medien
    Digitale Medien
    Analysis of lignin degradation products by capillary electrophoresis (1995)
    Springer
    Chromatographia 40 (1995), S. 51-57 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column electrophoresis ; Column liquid chromatography ; Phenolic lignin degradation compounds ; Sugar degradation products ; Quantitative analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A method for the quantitative analysis of phenolic lignin degradation products by capillary electrophoresis (CE) with on-column UV detection has been developed. The liquid biomass solutions contain low molecular hemicellulosic sugars and phenolic lignin degradation products with various degrees of polymerization. Special attention has been paid to the monomeric phenolic components of lignin degradation fragments, e.g. derivatives of phenolic acids, aldehydes, and alcohols. Uncoated fused silica capillaries and borate-phosphate buffer systems at moderate pH conditions were used in order to separate the compounds of interest. To provide validation of the method, the same samples were analyzed independently by HPLC using gradient elution on a RP-C18 column. As sugar degradation fragment, furan-2-carboxylic acid was detected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274608
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  • 138
    Digitale Medien
    Digitale Medien
    Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 85-90 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Phenolic compounds ; Ion-pair solid phase extraction ; On-line trace enrichment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 μg 1−1 and 20 μl−1 and limits of determination between 0.5 μg l−1 and 1 μg l−1 are obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274612
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  • 139
    Digitale Medien
    Digitale Medien
    Screening of water samples for polar organic micropollutants using on-column sample enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 631-637 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Trace analysis ; Pesticides in tap water ; Aromatic sulphonates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Methodology and instrumentation are described which allow chromatographic screening of water samples under substantially simplified conditions and at reduced cost. A single column is used to accomplish sample extraction, trace enrichment, and separation. The performance of such a system is demonstrated, and the results compared with conventionally used concepts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02315129
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  • 140
    Digitale Medien
    Digitale Medien
    Analysis of pyrithiones by reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 669-673 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02315135
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  • 141
    Digitale Medien
    Digitale Medien
    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276122
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  • 142
    Digitale Medien
    Digitale Medien
    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276127
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  • 143
    Digitale Medien
    Digitale Medien
    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276125
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  • 144
    Digitale Medien
    Digitale Medien
    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276129
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  • 145
    Digitale Medien
    Digitale Medien
    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276128
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  • 146
    Digitale Medien
    Digitale Medien
    Microcolumn liquid chromatography on carbon sorbents (1992)
    Springer
    Chromatographia 34 (1992), S. 173-176 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276133
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  • 147
    Digitale Medien
    Digitale Medien
    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276134
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  • 148
    Digitale Medien
    Digitale Medien
    Silanol group effect in C18 bonded phases in HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 182-184 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02276135
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  • 149
    Digitale Medien
    Digitale Medien
    Marked differences between acetonitrile/water and methanol/water mobile phase systems on the thermodynamic behavior of benzodiazepines in reversed phase liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 84-87 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Benzodiazepines ; Solvent effects ; ACN clusters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Two different methods were used to determine the separation factor α at different temperatures and the Gibbs-Helmholtz parameters (Δ(ΔH), Δ(ΔS)) of two adjacent benzodiazepines on a chromatogram were obtained from plots of lnα versus 1/T. We first studied each factor (fraction of water ϕ in the ACN/water mixture and column temperatureT), which controls the retention mechanism, and then we examined the simultaneous variation of all these factors. The changes in Δ(ΔH) and Δ(ΔS) in relation to a volume fraction of water ϕ in an ACN/water mixture were examined. In the ACN/water system, Δ(ΔH) was fairly constant in the acetonitrile region of ϕ≤0.52 and appears to be a roughly linear function of ϕ for ϕ≥0.52. In this system Δ(ΔS) is approximately a parabolic function of ϕ with an optimum at ϕ≅0.52. The retention mechanism of ten benzodiazepines was found to be significantly different in the methanol/water and ACN/water mixtures. The separation optimization of these ten benzodiazepines was then considered. A fraction of water of 0.43 in the ACN/water mixture and a column temperature of 44°C gave the most efficient separation conditions in the ACN/water mixture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02274199
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  • 150
    Digitale Medien
    Digitale Medien
    HPLC determination of urinary 2,4- and 2,6-toluendiamines as potential degradation products of polyurethane breast implants (1995)
    Springer
    Chromatographia 41 (1995), S. 661-664 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polyurethane degradation products ; 2,4- and 2,6-toluendiamine ; Urine analysis ; Breast implants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A reversed-phase HPLC method has been developed for the urinary determination of mutagenic 2,4- and 2,6-toluendiamines. These amines are degradation products of polyurethane, a material used to cover textured silicone breast implants. FMOC-Cl was used as fluorescent derivatising agent in order to obtain a limit of detection of 15 ng/ml in urine. Pre-treatment of urine samples was by liquid/liquid extraction and urine specimens of patients after surgury were analysed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02267801
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  • 151
    Digitale Medien
    Digitale Medien
    HPLC analysis of flavonoids and phenolic acids and aldehydes inEucalyptus spp. (1995)
    Springer
    Chromatographia 41 (1995), S. 657-660 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polyphenols ; Flavonoids ; Phenolic acids and aldehydes ; Eucalyptus spp.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Standards of the polyphenols occurring in wood, bark and leaf extracts ofEucalyptus spp. (i.e. flavonoids and phenolic acids and aldehydes) have been analyzed by HPLC using reversed phase columns, gradient elution and diode-array detection. The conditions used are reported.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02267800
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  • 152
    Digitale Medien
    Digitale Medien
    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268366
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  • 153
    Digitale Medien
    Digitale Medien
    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268367
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  • 154
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268371
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  • 155
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268369
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  • 156
    Digitale Medien
    Digitale Medien
    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268372
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  • 157
    Digitale Medien
    Digitale Medien
    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268374
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  • 158
    Digitale Medien
    Digitale Medien
    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268379
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  • 159
    Digitale Medien
    Digitale Medien
    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290233
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  • 160
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02268378
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  • 161
    Digitale Medien
    Digitale Medien
    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290235
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  • 162
    Digitale Medien
    Digitale Medien
    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290247
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  • 163
    Digitale Medien
    Digitale Medien
    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02290248
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  • 164
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Immunoaffinity chromatography ; Proteins ; Surface plasmon resonance detection
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278555
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  • 165
    Digitale Medien
    Digitale Medien
    Optimisation of post-column reaction detector for HPLC of explosives (1993)
    Springer
    Chromatographia 35 (1993), S. 5-12 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Post-column reaction detector ; Explosives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278550
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  • 166
    Digitale Medien
    Digitale Medien
    Optimizing separations in reversed-phase liquid chromatography by varying pH and solvent composition (1993)
    Springer
    Chromatographia 35 (1993), S. 18-32 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reverse phase ; Optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278552
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  • 167
    Digitale Medien
    Digitale Medien
    Separation and identification of fullerenes by liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 38-44 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Fullerenes ; On-line and off-line identification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278554
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  • 168
    Digitale Medien
    Digitale Medien
    HPLC determination of volatile phenols in wines (1993)
    Springer
    Chromatographia 35 (1993), S. 50-54 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Wine ; Volatile phenols
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278556
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  • 169
    Digitale Medien
    Digitale Medien
    Ion-pair LC of sugars at alkaline pH and pulsed electrochemical detection (1993)
    Springer
    Chromatographia 35 (1993), S. 61-66 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Sugars ; Ion-pair separation ; Pulsed electrochemical detection ; Hypercarb and PLRP-S
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278558
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  • 170
    Digitale Medien
    Digitale Medien
    Ion-pair LC of carbohydrates at alkaline pH. Separation and retention behaviour of glycoconjugates (1993)
    Springer
    Chromatographia 35 (1993), S. 55-60 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carbohydrates ; Ion-pair separation ; Glycoconjugates ; PRP-1 and PLRP-S
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278557
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  • 171
    Digitale Medien
    Digitale Medien
    The glycan patterns at the individual glycosylation sites in orosomucoid from allergic reaction patients (1993)
    Springer
    Chromatographia 35 (1993), S. 90-92 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; α1-acid glycoprotein ; Complex glycans ; Allergic reaction ; Terfenadine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278562
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  • 172
    Digitale Medien
    Digitale Medien
    A comparison of temperature and mobile phase composition effects for bonded liquid crystal and polymeric stationary phases in HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 85-89 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Bonded liquid crystals ; Polymeric stationary phases ; Variable temperature studies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278561
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  • 173
    Digitale Medien
    Digitale Medien
    Chromatographic comparison of the relative Lewis acidities of alumina and zirconia (1993)
    Springer
    Chromatographia 35 (1993), S. 133-138 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ligand exchange chromatography ; Zirconium oxide ; Aluminum oxide ; Lewis acids and bases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269691
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  • 174
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Formaldehyde in air ; Fluorimetric detection ; Comparison of fluorescent derivatives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269693
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  • 175
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; 18 β-glycyrrhetinic acid ; Glycyrrhizinic acid ; Toothpastes ; Solid phase extraction (SPE)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269697
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  • 176
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Amphetamine in plasma ; Enantiomeric separation ; Solid phase derivatization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269695
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  • 177
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Pre-column derivatisation ; Morpholine and degradation products ; Boiler feed water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269698
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  • 178
    Digitale Medien
    Digitale Medien
    An improved HPLC system for the analysis of photosynthetic pigments (1993)
    Springer
    Chromatographia 35 (1993), S. 189-192 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Carotenoid pigments ; Chlorophylls ; Photosynthestic tissue
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269701
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  • 179
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Monensins A and B ; Fermentation broth ; Streptomyces cinnamonensis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269704
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  • 180
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Ascorbic acid ; Antioxidant synergists ; Food, pharmaceuticals and cosmetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02269708
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  • 181
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Microdialysis ; Fermentation monitoring
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277511
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  • 182
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Enantiomer separation ; Stereospecific synthesis ; Crown ether phase ; Immobilized enzyme reactor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277507
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  • 183
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; Thin-layer chromatography ; Anti-hypoxia drugs ; Lipophilic character and retention
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277509
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  • 184
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Column liquid chromatography ; 1,4-Benzoxazin-3-ones ; Cyclic hydroxamic acids ; β-Cyclodextrin modified silica gel ; Enantiomer separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277514
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  • 185
    Digitale Medien
    Digitale Medien
    A particle size distribution analysis of used HPLC column packing material (1993)
    Springer
    Chromatographia 35 (1993), S. 295-301 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Used column packings ; Particle size distribution ; Scanning electron microscopy ; Column age
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Particle size distribution analysis and scanning electron microscopy (SEM) were carried out on eight used HPLC columns containing either irregular silica based, spherical silica based or spherical polymer based packing material. Particle size distributions of the used irregular silica based columns were at least bimodat at the outlet ends and either biomodal or log-normal at the inlet ends with regular progressions between the two extremes through the column. A new ODS-3 column showed log-normal size distributions from the inlet to the outlet ends. Spherical silica based column particle size distributions showed distinct shoulders on large central distribution peaks in most column sections with various degrees of shoulder erosion. The spherical resin based column showed a broader inlet particle size distribution progressing to a very narrow outlet distribution. SEMs of both irregular and spherical silica based columns revealed a larger number of undersized particles and debris at the outlet than inlet ends which could have resulted from stationary phase degradation, since this was not seen in the new ODS-3 column. While several SEMs of the spherical silica based columns revealed hollow spheres and twins, the spherical resin based column packing showed stress fractures or wrinkle lines resulting from use or dehydration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277513
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  • 186
    Digitale Medien
    Digitale Medien
    Simultaneous isolation and determination of esculin and rutin in natural materials using SPE and HPLC (1993)
    Springer
    Chromatographia 35 (1993), S. 311-316 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Isolation of natural products ; Solid phase extraction ; Chemically bonded phase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Esculin (ESC) and rutin (RUT) have been simultaneously isolated from pharmaceutical natural materials by solid phase extraction (SPE). Determination of both substances was performed by reversed phase high performance liquid chromatography (RPHPLC) with UV detection. Optimization of the separation conditions showed that simultaneous isolation and determination of rutin and esculin from pharmaceutical material was possible. The recovery obtained was not lower than 95±2%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277516
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  • 187
    Digitale Medien
    Digitale Medien
    Direct enantiomeric separation of racemic precursors to diltiazem hydrochloride and clentiazem maleate by HPLC on a chiral ovomucoid column (1993)
    Springer
    Chromatographia 35 (1993), S. 305-310 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Enantiomer separation ; Chiral ovomucoid column ; Diltiazem hydrochloride ; Clentiazem maleate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A direct HPLC separation method was developed for the determination of the enantiomers of racemic precursors to diltiazem (I) and its 8-chloro derivatives (II). The enantiomers were successfully separated on a chiral ovomucoid column using an aqueous-organic mobile phase (reversed-phase HPLC). The influence of the organic modifier and buffer pH on the retention and enantioselectivity was investigated. The chromatographic conditions chosen for the separation permitted complete resolution of the enantiomers of both the acid (Ib and IIb) and methyl ester precursors (Ia and IIa) within 20 min. The influence of sample load on retention times, theoretical plates numbers, peak heights and peak areas was also investigated. The peak areas showed a good linearity over the concentration range examined, although all the others were influenced significantly by the sample size. An optical antipode of the intermediate to be determined could be detected by the area-percentage method down to ca. 0.1%, together with the determination of its precursor, including its optical purity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277515
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  • 188
    Digitale Medien
    Digitale Medien
    Sensitive determination of probenecid in urine samples by reversed-phase liquid chromatography and UV-visible detection using solid-phase extraction techniques for sample clean-up (1993)
    Springer
    Chromatographia 35 (1993), S. 317-320 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Probenecid in urine ; Solid-phase extraction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary This study describes a rapid method for the determination of probenecid in human urine by liquid chromatography with UV detection at 254 nm, after clean-up through a C8 solid-phase extraction column. Liquid chromatography was carried out on a C18-bonded phase using an acetonitrile-acetate buffer (pH=4) gradient elution. Ethacrynic acid was used as internal standard. The system has been applied to the determination of probenecid in the 0.10–100.0 μg/ml concentration range; the limit of detection was 5 ng/mL.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02277517
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  • 189
    Digitale Medien
    Digitale Medien
    Effects of organic modifier and ion-pair reagent in liquid chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 390-394 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Electrostatic model ; Ion-pair reagent ; Organic modifier ; Prediction of k′ values
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The capacity factors of phenylamine and naphthylamine sulphonic acids in reversed-phase, ion-pair liquid chromatography (RP-IPC) were measured. The combined effects of organic modifier (Cb) and ion-pair reagent concentration (Cp) on retention follow an equation based on the electrostatic model: $$\ln k' = a + b lnC_p + cC_b $$ the experimental value of b correlates well with the value of 0.5 z (z=charge on analyte ion) predicted for mono and divalent ions. The measured value of b is, however, lower than that predicted for trivalent ions, which may be due to the effective number of charges being less than the apparent number. The absolute values of a and c are much larger than those in RP-HPLC in the absence of an ion-pair reagent, quantitative correlation of a and c with retention values in RP-HPLC and solute charges has been observed and a good linear relationship between a and c has been obtained, strongly supporting the validity of the electrostatic retention model. A critical value, R, at which the negative effect of methanol on retention is equal to the positive effect of the ion-pair reagent (TBAI) has been proposed. The critical values obtained are related to the behaviour of the solute, the ion-pair reagent and the stationary and mobile phases, and lies between −0.04 and −0.065 in most cases, which means that the increase by exp times (=2.718×) the ion-pair concentration the original is equivalent to a decrease of 0.04–0.065 in volume fraction of methanol
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278591
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  • 190
    Digitale Medien
    Digitale Medien
    Simultaneous determination of two serine proteinases by hydrophobic interaction chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 381-386 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Bovine trypsin ; Porcine kallikrein ; Bovine pancreatic trypsin inhibitor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The possibility of determining more than one enzyme at the same time has been examined. A new approach, based on the measurement of a direct and specific chromatographic signal obtained by hydrophobic interaction chromatography (HIC) of the stable complex formed with the inhibitor aprotinin, is proposed. A basic procedure for the quantitative determination of trypsin and kallikrein, taken as models, is described. The method is precise with a mean coefficient of variation of 3.1% and 3.5% for trypsin and kallikrein, respectively; the limit of determination for both enzymes is 0.17 nmol ml−1 in the original sample.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278589
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  • 191
    Digitale Medien
    Digitale Medien
    Influence of buffer composition on protein adsorption on agarose (Sepharose 6B) (1993)
    Springer
    Chromatographia 35 (1993), S. 387-389 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Buffer composition effect ; Agarose ; Albumin ; Ionic adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The adsorption of albumin on a commercial, high quality agarose (Sepharose® 6B) was studied in different buffers of low pH (4.00) and low molarity (9–11 mM). Eluents containing 0.025% albumin were introduced onto small gel columns until saturation and the adsorption capacity of the gel in different buffers calculated. Adsorption was high in solutions of monobasic acids. Although cation-exchange interactions between the protein and the gel matrix were found to be influenced essentially by the sodium ion concentration or ionic strength of the buffer, adsorption in cirate buffers is weak compared to that in formate, acetate or propionate buffers of about the same ionic strength (I=0.01).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278590
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  • 192
    Digitale Medien
    Digitale Medien
    Liquid chromatographic studies for essential fatty acids on a commercial alkyl phenyl bonded silica column (1993)
    Springer
    Chromatographia 35 (1993), S. 399-402 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Polyunsaturated fatty acids ; Direct injection ; Enthalpy of adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Retention studies on arachidonic acid 5, 8, 11, 14 all cis eicosatetraenoic acid, C20:4ω6), eicosapentaenoic acid (5, 8, 11, 14, 17 all cis eicosapentaenoic acid, C20∶5ω3) and docosahexaenoic acid (4, 7, 10, 13, 16, 19 all cis docosahexaenoic acid C22∶6ω3) were performed on a commercial μBondapak free fatty acid analysis column. The ternary mobile phase consisting of acetonitrile, water and tetrahydrofuran was used in an isocratic mode with differential refractometry detection. Retention data were mesured at various flow rates with two different, mobile-phase compositions. Capacity factors and enthalpy of adsorption were calculated from the retention data. Finally the retention mechanism is explained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278593
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  • 193
    Digitale Medien
    Digitale Medien
    A model for polybutadiene coatings on porous silica (1993)
    Springer
    Chromatographia 35 (1993), S. 403-409 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Reversed phase packings ; Polybutadiene coating ; Polymer coatings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Non-wetting viscous liquids such as oligobutadiene prefer “active” sites such as pores during the process of physisorption. Thus, polybutadiene (PBD) coatings on porous silica do not result in a homogeneous polymer film but in an inhomogeneous loading where the bulk polymer is mainly sited in the pores of the silica. An increasing polymer loading leads to increasingly filled pores instead of a thicker polymer film. We cannot exclude the possibility that most of the surface is covered at least with a thin polymer film since the chromatographic behaviour is relatively good for polypeptides, which are highly susceptible to the silanol groups of silica.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278594
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  • 194
    Digitale Medien
    Digitale Medien
    Highly sensitive method for the determination of a new anthracycline: Pirarubicin (1993)
    Springer
    Chromatographia 35 (1993), S. 435-438 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Pirarubicin and metabolites ; Anthracyclines
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A new and highly sensitive HPLC method for the simultaneous determination of pirarubicine (THP-doxorubicin) and its metabolites, adriamycin and adriamycinol, in human plasma, is described. Samples were treated by liquid-liquid extraction, the organic phase removed and the residue dissolved in methanol. Separation was on a Lichrocart Supersher RP 8 column, (250×4 mm) 4 μm, with a mobile phase of acetonitrile/methanol/formate-buffer.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278598
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  • 195
    Digitale Medien
    Digitale Medien
    The mechanism of separation of polythiolpeptides and metallopolythiolpeptides by covalent affinity chromatography (1993)
    Springer
    Chromatographia 35 (1993), S. 439-447 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Affinity chromatography ; Polythiolpeptides and metallopolythiolpeptides ; Mechanism of separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Covalent affinity chromatography with thiol-disulphide interchange (CAD-TDI) is a method for the separation of thiolproteins based on the interaction between disulphide bridges immobilised on a insoluble support and thiol groups in the protein undergoing separation. Mercury-thionein, cadmium-thionein and apothionein have been used as low molcular weight thiolproteins rich in cysteine residue. The proposed separation mechanism is more complex than those in the literature and can have anionic, cationic or a free radical character depending on the protein, the ligand and the conditions during separation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278599
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  • 196
    Digitale Medien
    Digitale Medien
    Determination of phenolic antioxidants in pharmaceutical formulations by liquid chromatography and migration study on HDPE packagings (1993)
    Springer
    Chromatographia 35 (1993), S. 455-458 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; UV and electrochemical detectors ; Phenolic antioxidants ; Migration studies
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The performance of UV diode-array, spectrometric and electrochemical detectors was compared in the chromatographic analysis of trace amounts of six phenolic antioxidants. Quantitative validation was undertaken; the linearity range was wider using UV detection although the limits of detection were lower with electrochemical detection. UV detection was applied both to identification of an antioxidant in a hydrophilic suspension and to a migration study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278602
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  • 197
    Digitale Medien
    Digitale Medien
    Quantitative structure chromatography relationships in reversed-phase high performance liquid chromatography: Prediction of retention behaviour using theoretically derived molecular properties (1993)
    Springer
    Chromatographia 37 (1993), S. 241-249 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Pattern recognition ; Principal components ; Multiple linear regressions ; M.O. properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The use of theoretically calculated molecular properties as predictors for retention in reversed-phase HPLC has been explored. HPLC retention times have been measured for a series of 47 substituted aromatic molecules in three solvent mixtures and steric and electronic properties of these compounds have been derived using semi-empirical molecular orbital and empirical theoretical methods. A subset of the experimental data (a training set) was used to derive property-retention time relationships and the remaining data were then used to test the predictive capability of the methods. Good retention time prediction was possible using derived regression equations for individual solvents and after including solvent parameters it was possible to predict retention for all solvents using a single equation. This method showed that the most useful properties were calculated log P and the calculated dipole moment of the solutes, and the calculated solvent polarisability. In addition, 90% of the data were used to train an artificial neural network and the remaining 10% of the data used to test the network; excellent prediction was obtained, the neural network approach being as successful as the regression analysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278628
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  • 198
    Digitale Medien
    Digitale Medien
    Composition of 2-(3,5-dibromo-2-pyridylazo) diethylaminophenol chelates by liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 284-286 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Composition of chelates ; 3,5-diBr-PADAP
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The composition of 3,5-diBr-PADAP metal chelates was determined by liquid chromatography employing appropriate eluents and non-polar bonded stationary phase. The metal-to-ligand ratios were 1∶2, 1∶2 and 1∶2 for Cu(II), Co(III) and Cr(III) respectively, and the V(V)-to-ligand ratio found to be 1∶1∶1 in V(V)-3,5-diBr-PADAP-H2O2 in the presence of H2O2. The results are in agreement with literature data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02278635
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  • 199
    Digitale Medien
    Digitale Medien
    HPLC determination of chlorine in air and water samples following precolumn derivatization to 4-bromoacetanilide (1993)
    Springer
    Chromatographia 37 (1993), S. 492-496 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Chlorine in air and water ; Precolumn derivation ; 4-Bromoacetanilide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Chlorine has been be determined in air and water samples by a rapid and sensitive method entailing precolumn derivatization to 4-bromoacetanilide. A mixed potassium bromide-acetanilide reagent was used as a trapping agent for chlorine in air, and for its derivatization. The 4-bromoacetanilide formed was determined by reversed-phase HPLC on an ODS column, using methanol-water, 65∶35 (v/v) as mobile phase; detection was at 240 nm. A rectilinear calibration graph was obtained for the range 0.1–30 μg mL−1 chlorine; the limit of detection found to be 0.01 μg mL−1. The precolumn derivative has been found to have a shelf-life of at least 21 days; this enables the use of the method for samples transported from the field to the analytical laboratory, or the testing of a variety of conditions for chlorine scrubbing studies without the need for immediate analysis of samples. Humic substances do not cause any interference with the proposed method and the presence of nitrite does not lead to artificially high results and consequent misleading conclusions of the presence of high levels of chlorine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275785
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  • 200
    Digitale Medien
    Digitale Medien
    Polymers immobilized on silica gels as stationary phases for liquid chromatography (1993)
    Springer
    Chromatographia 37 (1993), S. 549-561 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Stationary phases ; Polymer-coated silica ; Polymer-filled silica
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A variety of stationary phases for HPLC can be prepared by immobilization of organic polymers on silica gels. Such silica-polymer adsorbents combine the strength of an inorganic matrix with the selectivity and chemical inertness of organic resins. Moreover, effective shielding of residual silanols and the increase of column packing stability can also be achieved by modification of silica gels with organic polymers. There are two main approaches to the preparation of such composite sorbents. The first includes various routes for coating the silica surface with a polymer layer and the second is by filling the silica pores with a polymer network. A survey of polymers immobilized on silica gels and of various experimental procedures which can be used for composite sorbent synthesis is given in this review.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02275796
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