摘要:

The separation behaviors of four different groups of pharmaceuticals were investigated using cholesteryl-10-undecenoate and ODS phases. The cholesteryl phase, which has liquid crystal properties, showed different selectivity and retention behavior from those of ODS phase. The difference is on its apparent ability to recognize specific structures in the molecules, discriminate among derivatives, or subsequently recognize modifications done on these structures. However, on ODS phase the hydrophobicity effects seem to take precedent as the main factor in its retention mechanism. This enhanced selectivity of the cholesteryl phase is attributed to three contributing structures found in its structure; the long hydrocarbon chain that gives added mobility to the phase, the carbonyl group which can interact with a variety of substituent groups, and the cholesteric moiety which can invoke π-π interaction as well as steric effects. The use of the cholesteryl phase for these kinds of pharmaceutical analyses is therefore warranted and showed interesting possibilities for future applications.

ISSN:1082-6076    

DOI:10.1081/JLC-100101710

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The chromatographic behavior of aprotic neutral molecules in Ion Interaction Chromatography (IIC) was investigated both theoretically and experimentally on a styrene-divinylbenzene based C18stationary phase. The chemical modification of the stationary phase in the presence of Ion Interaction Reagent (IIR) in the eluent, and adsorption competition between tested analytes and IIR for inner layer sites are theoretically shown to change the partition coefficient for neutral molecules.

ISSN:1082-6076    

DOI:10.1081/JLC-100101711

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A method for the determination of a macrolide immunosuppressant, L-732,531, in plasma is described. Plasma samples are extracted using cyano solid phase extraction columns. The extract is analyzed by normal phase high performance liquid chromatography with a cyano column and a mobile phase of hexane/2-propanol/water (780:220:3). Detection is based on fluorescence at an excitation wavelength of 276 nm and an emission wavelength of 330 nm. The limit of quantification of the assay is 1 ng/mL. The assay was validated in the concentration range of 1 – 200 ng/mL when 1 mL aliquots of plasma are extracted.

ISSN:1082-6076    

DOI:10.1081/JLC-100101712

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Enantiomers of chiral spiro-λ4-sulfanes with equatorial diaryl and axial bis(acyloxy), (alkoxy)-(acyloxy) or (acylamino)-(acyloxy) S-substituents were separated on a Kromasil-based chiral sorbent, namely on O,O′-bis(3,5-dimethylbenzoyl)-N,N′- diallyl-L-tartardiamide silica CSP, by using n-hexane (or n-heptane) – dioxane (or 2-propanol) isocratically mixed mobile phases. Direct chiral separation was monitored by a home-made HPLC-CD system consisting of a circular dichroism (CD) spectrophotometer (Jobin-Yvon Model III Dicrograph) and a high performance liquid chromatograph. The system was used in conjunction with HPLC-UV to study the chemical and stereochemical purity of the samples. By the stopped-flow technique CD spectra were measured in the 350–230 nm spectral range. Monitoring at a selected wavelength enabled high-sensitivity detection. Racemic spiro-λ4-sulfanes were also separated into pure enantiomers on preparative scale. Regardless of the structural type of diaryl-spiro-λ4-sulfanes, the first-eluted enantiomer was always found to show a CD spectrum marked by an intense positive band near 240 nm and a negative one at ≈210 nm (positive couplet) that allows prediction of absolute configuration.

ISSN:1082-6076    

DOI:10.1081/JLC-100101713

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new procedure for the amino acid analysis of peptides has been devised utilizing high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD). This procedure eliminates the need for complex derivatization schemes inherent of previous amino acid analysis procedures since the ELSD detects the amino acids directly. This quantitative method detects and separates 18 of the common amino acids in a one hour run time using cation exchange chromatography coupled with ELSD. The procedure was tested by analyzing the hydrolysate of human parathyroid hormone 1–34 (PTH), a synthetic polypeptide. A standard digestion consisting of 24 hour hydrolysis at 110°C in 6 N hydrochloric acid with 3% phenol was used. Validation data reveal this is an accurate and precise procedure for the amino acid analysis of peptides.

ISSN:1082-6076    

DOI:10.1081/JLC-100101714

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Recently capillary electrophoresis (CE) has been used for the separation and detection of toxic heterocyclic aromatic amines (HAA) that are present in several environmental samples and food samples. Methods found in the literature were studied and compared in detail, and the conditions for the improved separation of a group of eight HAA are discussed. The effects of buffer pH and the concentration of the organic modifier (methanol and acetonitrile) on the separation and elution order of the HAA were also studied. In addition, for the first time, the running buffer was modified with α-, β-, and γ-cyclodextrin. The overall separation was improved with β-cyclodextrin, and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) gave the strongest interaction.

ISSN:1082-6076    

DOI:10.1081/JLC-100101715

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Stationary phase based ontris(3,5-dimethylphenylcarbamoyl) cellulose is prepared under various conditions (precipitation, evaporation, sieving), and examined in HPLC columns for enantioseparation of racemic mixtures 1–10. Number of theoretical plates (N) and separation parameters (α and RS) are compared with those obtained with commercially available column based on the same polymeric material (Chiralcel OD, from Daicel Co.). Higher efficiency of the columns prepared by precipitation under specific conditions and followed by sieving of stationary phase, over those prepared by evaporation and (or without) sieving, is demonstrated.

ISSN:1082-6076    

DOI:10.1081/JLC-100101716

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A solid phase extraction procedure using strong cation exchange (SCX, benzenesulfonic acid) cartridges followed by a reversed-phase HPLC assay was applied to the analysis of hyoscine n-butylbromide and lidocaine hydrochloride in injection forms. The chromatographic separation was performed on a BDS C-18 column. The mobile phase consisted of a mixture of acetonitrile: ammonium acetate 0.2M, (30:70, v/v) pumped at a flow rate 1.2 mL/min. The UV detector was operated at 254 nm. A UV-Vis spectrophotometric method was also developed for the determination of paracetamol in the injection forms. The method consists of subsequent dilution of the injection forms and measure of the absorbance value at 242.7 nm. Relative standard deviation was less than 0.95% for HPLC and less than 0.78% for the spectrophotometric method. Detection limits were 1.05, 0.96 and 0.67 μg/mL for hyoscine n-butylbromide, lidocaine hydrochloride and paracetamol, respectively.

ISSN:1082-6076    

DOI:10.1081/JLC-100101717

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple, rapid, sensitive, reproducible, and accurate reversed-phase HPLC procedure is proposed for the determination of sodium benzoate in quince jam samples. The sample preparation was simple, involving only extraction with methanol. The chromatographic separation was achieved using a reversed-phase column Spherisorb ODS2 (5μm; 25.0 × 0.46 cm). Gradient elution was carried out using water-formic acid (19:1) (A) and methanol (B). The effluent was monitored by a diode-array detector and chromatograms were recorded at 280 nm. The detection limit value of the method for sodium benzoate was 0.5 μg/mL and the method was precise (SD=0.003; CV%=2.76; n=6). Recovery values of sodium benzoate from spiked quince jam samples were between 94.7 and 100 %. This technique can also be useful for the simultaneous definition of the phenolic profile (phenolic acids, flavonoids, and glycosides of procyanidin polymers) of quince jam.

ISSN:1082-6076    

DOI:10.1081/JLC-100101718

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The amino acid compositions were determined in four different algal species: the temperateThalassiosira rotulaandPhaeocystis globosaand the polarThalassiosira antarcticaandPhaeocystis antarctica.

ISSN:1082-6076    

DOI:10.1081/JLC-100101719

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor