摘要:

A complex mechanism of the reverse-phase chromatography can be envisioned as a combination of partition and adsorption processes. In the partition-displacement (P-D) model, partition accounts for the distribution of solute between the mobile and stationary phases, while displacement mostly involves competitive adsorption of solvents in the stationary phase. Therefore, chromatographic properties of a given stationary phase are largely dependent on the intercalation of solvents in the surface layer. The current work is a continuation of the ongoing studies of the factors affecting the surface composition of the stationary phase. Specifically, the goal of this work was the investigation of chromatographic behavior of two octyl phases of a similar surface coverage, which were synthesized from different silica supports. Analysis of methylene selectivity data showed that sorption of acetonitrile on both octyl phases was similar. This outcome could be related to a significant similarity of their structural and surface properties as demonstrated by analysis of the corresponding nitrogen adsorption and solid-state NMR data.

ISSN:1082-6076    

DOI:10.1081/JLC-100101777

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Chromatographic behaviors of amino acids and peptide derivatives were examined by high performance hydrophobic interaction chromatography(HIC) on two different packings,TSKgels Phenyl–5PW and Ether–5PW. Most amino acids hardly retained and eluted at an elution volume being the same as the column volume even with an initial buffer for hydrophobic interaction chromatography; aromatic amino acids showed weak retention. On the other hand, peptides retained in the column and their elution was roughly in the order of the molecular mass, although some of them showed extraordinary elution behaviors. Kunitz bovine pancreas trypsin inhibitor showed weak retention in spite of having larger molecular mass, which might be due to the steric conformation.

ISSN:1082-6076    

DOI:10.1081/JLC-100101778

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A micellar electrokinetic capillary chromatography method is presented to separate sulfamethazine, sulfaquinoxaline, menadione, and pyrimethamine. Separation was carried out at 20 kV for the five first minutes and then rised to 30 kV until the end came, using 30 mM borate buffer adjusted to pH 9.2, 6% acetonitrile, and 40 mM sodium dodecyl sulfate as electrolyte.

ISSN:1082-6076    

DOI:10.1081/JLC-100101779

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Normal-phase preparative HPLC was applied to the purification of nitrendipine and its dimethyl ester from raw materials. For each separation, the chromatographic conditions were optimized by adjusting the sample size to achieve an efficient purification with a yield of 99% in the shortest time. The contaminating impurities were removed in a single step by preparative chromatography. This work demonstrates how gram quantities of analytically pure materials can be conveniently obtained using preparative HPLC.

ISSN:1082-6076    

DOI:10.1081/JLC-100101780

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The linkage-region oligosaccharides of chondroitin sulfate and dermatan sulfate, produced by the action of various chondroitinases, as well as of heparan sulfate, produced by the combined action of heparin-lyases I, II, and III, have been separated and characterized according to their size, number of sulfate residues, and the presence of phosphorylated xylose by HPLC. Glycosaminoglycans and/or proteoglycans were treated by tritiated borohydride and the [3H]-labeled xylitole-containing glycan chains were degraded by the various chondro/dermato-lyases (chondroitinases ABC, AC and B) and/or heparin-lyases. The produced linkage-region Δ-oligosaccharides have been completely separated by ion-pair reversed phase HPLC, using tetrabutylammonium as ion-pairing reagent, and detected by a radiochemical detector.

ISSN:1082-6076    

DOI:10.1081/JLC-100101781

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A simple and rapid isocratic high-performance liquid chromatographic method has been developed for the simultaneous analysis of the non-steroidal anti-inflammatory drugs tenoxicam, piroxicam, meloxicam, and lornoxicam using isoxicam as an internal standard. The analyte was chromatographed using a Lichrosphere RP18 column, a Tris acetic acid buffer-tetrabutylammonium reagent-tetrahydrofuran-acetonitrile as the mobile phase, and UV detection at 360 nm. The separation obtained was very good. The method was applied to pharmaceutical formulations containing a single active ingredient and was shown to be linear, sensible, accurate, and reproducible. A very small modification of the mobile phase enabled the separation of tenoxicam, piroxicam, isoxicam, cinnoxicam,meloxicam, and lornoxicam with symmetrical and well resolved peaks.

ISSN:1082-6076    

DOI:10.1081/JLC-100101782

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A rapid, accurate, and sensitive method has been developed for the simultaneous determination of nitrite and nitrate. A low capacity strong anion exchange PRP-X100 Hamilton, 150 × 4.1 mm, 10 μm, with exchange capacity 0.19 ± 0.02 meq/g, analytical column was used, with a mixture of 0.1 M NaCl-CH3OH, at a volume ratio 45:55. The flow rate of 2 mL/min, lead to a pressure of 150 kg/cm2. Detection was performed with a variable wavelength UV-visible detector, at 230 nm, resulting in detection limits of 0.1 ng and 0.2 ng for nitrite and nitrate, respectively, per 20 μL injection. For the quantitative determination, iodide was used as internal standard, at a concentration of 7.0 ng/μL. A rectilinear relationship was observed up to 12 ng/μL for nitrite and up to 25 ng/μL for nitrate. Analysis time was less than 6 min. The statistical evaluation of the method was examined performing intra–day (n = 8) and inter-day calibration (n = 8) and was found to be satisfactory, with high accuracy and precision results.

ISSN:1082-6076    

DOI:10.1081/JLC-100101783

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A rapid method for the determination of cotinine concentration in plasma is described. Cotinine is extracted from plasma along with 2-phenylimidazole as an internal standard. Extraction is accomplished by solid phase extraction using BondElut C18silica extraction columns. The extract is evaporated, reconstituted with mobile phase, and injected onto a reversed-phase C18ion-pair column using an isocratic high performance liquid chromatograph. The mobile phase consists of acetonitrile and methanol in phosphate buffer (0.01M, pH 3.2) 7:13:80 (v/v/v) containing octanesulfonic acid (0.001 M). The flow rate was 1.5 mL/min. Absorbance was monitored at 260 nm. The detection limit is 5 μg/L for cotinine. The standard curve is linear from 0 to 1000 μg/L. The CVs at 40 μg/L and 100 μg/L are 7.4% and 4.8% respectively.

ISSN:1082-6076    

DOI:10.1081/JLC-100101784

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

A new, simple, precise, accurate, rapid, and stability indicating high performance thin layer chromatography (HPTLC) method has been developed for the simultaneous determination of pyridoxine hydrochloride and doxylamine succinate in tablets. The stationary phase was silica gel 60F254HPTLC plates and the mobile phase was acetone - chloroform - methanol - 25% ammonia solution (7 : 1.5 : 0.3 : 1.2, v/v). Detection and quantification was carried out densitometrically at 269 nm. The linearity ranges were 0.5–2.0 μg/spot for both pyridoxine hydrochloride and doxylamine succinate. Assays for pyridoxine hydrochloride and doxylamine succinate were 10.20 mg/tab (RSD 0.73%) and 10.00 mg/tab (RSD 1.93%) respectively for the brand analyzed. Percentage recoveries of pyridoxine hydrochloride and doxylamine succinate were in the range of 99.30–103.00% and 97.70–101.00%, respectively.

ISSN:1082-6076    

DOI:10.1081/JLC-100101785

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The α-diketones glyoxal, methylglyoxal, and diacetyl were determined in selected beer and wine using a procedure involving the use of C18solid phase extraction columns to remove interferences and derivatization of the compounds with o-phenylenediamine to form quinoxalines, which are separated by HPLC and detected using UV spectrophotometric detection.

ISSN:1082-6076    

DOI:10.1081/JLC-100101786

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor