摘要:

This paper shows how a porous graphitized stationary (PGC) phase can be modified to work in RP-HPLC ion-interaction reagent (IIR) mode. Aqueous solutions of alkylammonium o-phosphate salts are used as IIRs and the analytes are the inorganic anions, iodide, iodate, bromide, bromate, nitrite, and nitrate.

ISSN:1082-6076    

DOI:10.1081/JLC-100101821

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The main limitation of multi-detector GPC arises from the nature of detector sensitivities in the tails of a polymer distribution. In the low molecular weight tail of this distribution, molecular weight-sensitive detectors (such as a capillary viscometer or a static laser light-scattering photometer) have low sensitivity while concentration detectors (e.g., differential refractometer) have high sensitivity. This situation is reversed in the high molecular weight tail.

ISSN:1082-6076    

DOI:10.1081/JLC-100101822

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The chiral recognition mechanism for a derivatized polysaccharide chiral stationary phase (CSP) under reversed phase conditions was investigated (Chiralcel OJ-R). While enantiorecognition mechanisms have been proposed for these types of phases under normal phase conditions, it is unlikely that they would apply to reversed phase conditions due to the high polarity of the eluent. Indandiol was utilized as the main probe. The effect of organic modifier, eluent anion, and temperature on enantioselectivity for indandiol was determined. Additionally, a number of structurally related probes were also investigated to define the role of various functional groups on enantioselectivity.

ISSN:1082-6076    

DOI:10.1081/JLC-100101823

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The non-linear calibration in quantitative determinations by high performance thin-layer chromatography utilizing a fibre optic fluorescence detector is examined. Dansyl derivatives of polyamines, as model compounds, are separated in HPTLC silica-gel plates with chloroform:triethylamine (TEA):polyoxyethylene-10-lauryl ether (POLE) (8:4:5%) (v:v:m) as solvent. The obtained calibration graphs show a non-linear relationship between the fluorescence intensity and the quantity of the amine (0-150ng).

ISSN:1082-6076    

DOI:10.1081/JLC-100101824

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A dynamic chiral stationary phase (CSP) prepared by hydrophobically bonding N-dodecyl diamide of (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid to octadecyl silica gel was successfully employed in resolving various racemic compounds containing a primary amino functional group. The racemic compounds resolved on the CSP include α-amino acids, α-amino esters, amino alcohols, amines, α-aminocarbonyl compounds, and fluoroquinolone antibacterial agents.

ISSN:1082-6076    

DOI:10.1081/JLC-100101825

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

In this study, we reported a chromatographic protocol using C18silica gel phase and basic Al2O3phase to research the creating and recovery of taxol from the extract ofTaxus cuspidatecallus cultures. With the cleaning up by basic Al2O3chromatography, the content of taxol determined in our experiment was increased greatly. The main source of increasing taxol concentration was the isomerization of 7-epi-taxol to taxol; taxol could also be decomposed to baccatin III and 10-deacetylbaccatin III in the Al2O3column. At the optimized conditions, the total recovery of taxol from the extract was more than 160%.

ISSN:1082-6076    

DOI:10.1081/JLC-100101826

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Spectrophotometric and liquid chromatographic methods were used to determine anthocyanin and organic acid content and composition of commercial Finnish cranberries (Vaccinium oxycoccosL.). Solid-phase adsorbents were used in the fractionation of juice components prior to chromatographic determination. In the freshly prepared cranberry juice the total amount of anthocyanins was 7.7 mg/100 mL juice determined spectrophotometrically at 510 nm. The most abundant individual anthocyanins were cyanidin-3-galactoside (19.2%), cyanidin-3-arabinoside (23.1%), peonidin-3-galactoside (21.5%) and peonidin-3-arabinoside (14.1%), as determined by RP-HPLC.

ISSN:1082-6076    

DOI:10.1081/JLC-100101827

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

High performance liquid chromatography (HPLC) assays are described for measuring the catalytic activities of chorismate-pyruvate lyase andp-aminobenzoate synthase (EC 4.1.3.-), enzymes involved in the ubiquinone and folate biosynthetic pathways, respectively. These assays allow rapid and accurate detection of substrate consumption and product formation. Also depletion of chorismate and the presence of other interfering chorismate utilizing enzyme activities can be observed. The detection limit for the productsp-hydroxybenzoate andp-aminobenzoate is 2.5 ng for both. The suitability of the assays is demonstrated with extracts fromEscherichia coli.

ISSN:1082-6076    

DOI:10.1081/JLC-100101828

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Racemic aminoglutethimide and acetylaminoglutethimide were resolved on a fluorescent Silica gel 60A TLC plate using 30% hydroxy trimethylpropylammonium-β-cyclodextrin with methanol (50:50v/v) as the mobile phase. Also, the resolution of the enantiomers of aminoglutethimide as dansyl derivatives were investigated on reversed phase TLC using a mobile phase consisting of a β-cyclodextrin solution (0.05 M saturated with urea), or 15% (carboxymethyl-β-cyclodextrin) solution with methanol (65:35v/v). Enantiomeric resolution was found to be highly dependent on mobile phase composition. The effect of the type and amount of organic modifier as well as the concentration of β-CD derivative, and the pH of the mobile phase on resolution were studied. Three types of maltodextrins failed to show resolution for any of the racemic compounds studied.

ISSN:1082-6076    

DOI:10.1081/JLC-100101829

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

High performance thin layer chromatography (HPTLC) is used to rapidly determine the presence and amount of ergovalin in seeds ofGraminaceaeinfested withNeotyphodium Coenophialum.Quinine is used as an internal standard. The mycotoxin is solubilized under acid conditions and extracted with chloroform under alkaline conditions. Samples are sprayed on silica gel plates and detected by fluorescence with λ1(excitation) set at 318 nm and λ2(emission) > 400 nm.

ISSN:1082-6076    

DOI:10.1081/JLC-100101830

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor