摘要:

Solute-solute interactions, due to self-association as well as mixed association, are shown to arise for the steroids cortisone, tetrahydrocortisol, tetrahydrocortisone, and methylprednisolone. From molecular mechanics and dynamics simulations, these interactions appear to be driven by strong electrostatic and hydrogen bonding forces. These interactions have a significant effect on solute retention and dispersion behavior under routine operating conditions in reverse-phase liquid chromatography.

ISSN:1082-6076    

DOI:10.1080/10826079608017140

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We have examined the effect of mobile phase conditions on the elution and recovery of proteins from a carboxymethyl dextran coated zirconia stationary phase. Mobile phases containing the Lewis bases phosphate and fluoride were examined as a function of concentration. We found that proteins only eluted from the stationary phase when some minimum concentration of Lewis base was present in the mobile phase. The effect of ionic strength was also examined. We found that a fairly high ionic strength is needed to elute the proteins with good recovery. The concentrations of the Lewis bases and the ionic strength needed to elute the proteins depended on the identity of the protein and the Lewis base. The pH of the mobile phase also plays a role; when the pH of the system is below the isoelectric point of a protein, it is difficult to elute that protein.

ISSN:1082-6076    

DOI:10.1080/10826079608017141

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Problems associated wtih poor baseline recovery between the end of the polymer chromatogram and the beginning of the solvent impurity peaks are discussed, and an approach for accurate calculation of molecular weight averages of polymers is described. Polystyrene SRM 706, where the presence of low molecular weight materials is suspected, was used as a sample polymer by way of example. Tetrahydrofuran and a refractometer were used as mobile phase and detector, respectively. Although a stable baseline was obtained under the appropriate conditions, baseline resolution was not obtained at the end of the polymer chromatogram, and the peak-end response was flat and parallel to the extrapolated baseline. The reason for no baseline resolution was found to be due to the existence of low molecular weight materials, by measuring the chromatogram of the polymer from which low molecular weight materials were removed. Inclusion of the response below molecular weight (MW) 2000 resulted in extremely low values of number-average MW.

ISSN:1082-6076    

DOI:10.1080/10826079608017142

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

We have examined the separation of test mixtures by linear and step temperature gradients in open tubular capillary liquid chromatography, in reverse and normal-phase modes. Separations using temperature gradients with the upper temperature limit of 433 K were compared to isothermal runs in terms of chromatographic efficiency, analysis time and selectivity. When a temperature gradient (363 K to 433 K in 12 min) was utilized in reverse phase separation of chlorobenzenes, a 40% reduction in analysis time, compared to an isothermal separation at 363 K, was accomplished.

ISSN:1082-6076    

DOI:10.1080/10826079608017143

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Two isolectins from the lichenXanthoria parietina, one of them retained by the thallus and another secreted from the thallus to the medium, both showing arginase activity, have been purified to homogeneity. Ethanol-soluble products obtained after acidic hydrolysis of both proteins have been analyzed by HPLC under isocratic conditions using acetonitrile-water (80:20, v/v) as mobile phase. Detection is performed by measurement of UV absorbance at 195 nm, using a highly sensitive detector. Purification of standard sugars by filtering aqueous solutions through an activated alumina column is absolutely required. The glycosyl moiety of secreted arginase is composed by galactose and glucose whereas that of thalline enzyme contains N-acetyl-D-glucosamine and glucose.

ISSN:1082-6076    

DOI:10.1080/10826079608017144

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A series of triphenylethylene derivatives was studied with different reverse phase liquid chromatographic columns. Octyl and octadecyl silica stationary phases were compared, as well as, one type of polymeric reverse phase. Because these triphenylethylene derivatives appear highly lipophilic, the polymeric column (PRP-1) did not produce satisfactory peaks. Also, the basic nature of these molecules requires such column properties that were most satisfactorily met by well end capped octyl silane phase columns, like Kromasil C8or deactivated Supelco LC-8-DB. These columns will be suitable for evaluating lipophilicity data of triphenylethylene derivatives, in order to use them in quantitative structure-activity relationship studies.

ISSN:1082-6076    

DOI:10.1080/10826079608017145

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A chemometric method, Kalman filtering, was applied to deal with three-dimensional electropherograms, obtained by capillary electrophoresis connected to a charge-coupled device multiwavelength fluorescence detector. The capillary electrophoretic peaks of a mixture, which were not effectively separated, were resolved into electrophoretic peaks of individual components to obtain qualitative and quantitative information. The approach has been applied to analyze a mixture of rhodamine fluorescent dyes with excellent results.

ISSN:1082-6076    

DOI:10.1080/10826079608017146

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A sensitive and selective reverse phase high performance liquid chromatographic (HPLC) method was developed for the determination of the enantiomers of ibuprofen in human plasma. Ibuprofen and fenoprofen (internal standard, ISTD) are extracted from human plasma by n-butyl chloride, following acidification of plasma. The method is based on the separation of the diasteromers formed on reacting ibuprofen enantiomers and ISTD with S-(-)-1-(1-naphthyl)ethylamine. Separation is achieved by HPLC on an Inertsil ODS-2 column, with a mobile phase composed of water (pH 3.0):ACN (33.5:66.5). Detection is by fluorescence detection with excitation and emission at 280 and 320 nm, respectively. The mean retention times of S-(+)-ibuprofen, R-(-) -ibuprofen, S-fenoprofen and R-fenoprofen (ISTD) are approximately 11.3, 12.3, 7.7 and 8.5 minutes, respectively.

ISSN:1082-6076    

DOI:10.1080/10826079608017147

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A precise and selective method for determining the content of thiamine in dietetic and baby foods by reverse phase liquid chromatography with UV detection is proposed. Enzymatic extracts of food samples were subjeted to purification and preconcentration with a weak ionic exchange column (CBA) and 0.1 M BaCl2solution as eluent. Ion-pair chromatography using a C18column and a mixture of 5 mM sodium hexanesulphonate as counter-ion, 10−-2M potassium dihydrogen orthophosphate/ phosphoric acid buffer solution, pH 2.8, and 0.1% triethylamine was employed. The thiamine was detected at 254 nm.

ISSN:1082-6076    

DOI:10.1080/10826079608017148

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Detection ofClostridium botulinumneurotoxin-producing strains is primarily accomplished using the mouse bioassay. The polymerase chain reaction (PCR) method has proven to be a rapid, sensitive technique for amplifying target DNA sequences of pathogenic microorganisms. Four PCR-amplified gene fragments derived from theClostridium botulinumType E neurotoxin gene, ranging from 410–630 bp, were analyzed by capillary gel electrophoresis (CGE). Sample preparation of PCR fragments required membrane dialysis to remove salt ions. PCR fragments were analyzed by CGE using both linear and covalently cross-linked polymers. Conditions for low-viscosity entangled polymer solutions were optimized to achieve the desired separation efficiency. Assessment of both types of polymer systems included resolution, reproducibility, and sizing accuracy of the PCR fragments. Advantages and limitations of each polymer system are discussed. Electropherograms were compared to results obtained from the agarose slab gel method. CGE afforded more rapid analytical times, automation, higher resolution, and increased DNA sizing accuracy in comparison to the agarose slab gels.

ISSN:1082-6076    

DOI:10.1080/10826079608017149

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor