摘要:

Four metallothioneins (MTs), rabbit liver MT (RL), MT-1 (RL 1) and MT-2 (RL 2) and horse kidney MT (HK), were subjected to reverse phase HPLC with on-line UV and electrochemical (EC) detection, the latter comprising of a graphite electrode. The EC detection is based on the direct oxidation of the thiols contained in the MT chains, into disulphides. MT samples were prepared at different pH values and eluted with a gradient of TFA and acetonitrile. The MTs are found to exhibit a different polymorphism and the various peaks differ in their detectability depending on the detection mode. RL 2 (one major peak) and HK (three peaks) have peak patterns which are stable with time and varying pH, all peaks being detected by both EC and UV modes. The two other MTs also exhibit peaks which are eluted within the same retention time range as the previously mentioned MTs and which give EC and UV signals (three peaks for RL 1 and four for RL), but which also show some other peaks - eluted earlier - which are perfectly detected in UV but not or very little in EC. This latter information means that these species contain none, or very few, thiol groups. Stable with time at neutral and basic pH, the RL 1 and RL chromatograms are highly evolutional in acid pH with the formation of more of the non-EC detected species and a decrease in the doubly detected ones. We can therefore assume that the peaks detected by both EC and UV modes correspond to the original thiol containing isoforms, while those less hydrophobic of RL 1 and RL correspond to modified species, probably containing disulphide bonds which explains the lack of EC response at the graphite electrode. Since many MTs are highly reactive, this UV/EC combination appears to be a very good tool for a quick identification of reduced (thiolic) isoforms from oxidised (with disulphides) species.

ISSN:1082-6076    

DOI:10.1080/10826079608015809

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

L-Ascorbic acid is a difficult vitamin to quantitate by HPLC due to its low retention and poor resolution using the previously available column technologies. This is particularly evident in aquatic feed and meals, where various interferences deter the vitamin's accurate determination and quantitation. Furthermore, these matrices often contain other 'stabilized' forms of vitamin C, necessitating several determinations utilizing a variety of chromatographic methods.

ISSN:1082-6076    

DOI:10.1080/10826079608015810

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Usually, determination of DOPEG in plasma by EC-HPLC is always performed after extraction on alumina. This paper presents an extraction on boric acid gel, with good selectivity, reproducibility. In high sensitivity conditions (0.5 nA full scale) an autosampler is used and presents two major advantages: first, the possibility of storing samples in cold conditions to preserve stability of DOPEG, second the analysis of numerous samples in pharmacological studies, for example.

ISSN:1082-6076    

DOI:10.1080/10826079608015811

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A simple reflectance densitometric method for quantitation of polar and non-polar lipids was developed, by thin layer chromatography (TLC) or high performance TLC. The solvent systems used were a mixture of n-hexane:diethylether: glacial acetic acid (80: 20: 1, V/V) for non-polar lipids and chloroform: methanol:water (65:25:4, V/V) for polar lipids. After removal of solvents, lipid fractions were visualized by exposing the plate to iodine vapor. The plate was then covered with a glass plate and scanned at 365 nm. Different lipid fractions were quantitated by using appropriate reference standards. Iodine color is stable for at least three hours; the integrated area values of the lipid components are linear with their concentrations with a variation of 2 to 4 percent. The method of quantitation being nondestructive, the TLC plates may be used for further studies.

ISSN:1082-6076    

DOI:10.1080/10826079608015812

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A rapid, sensitive and selective method for determining 13 PAHs in drinking water samples using solid-phase extraction and HPLC with programmed fluorescence detection is developed. A solid-phase extraction method is described for preconcentrating the PAHs on Sep-Pak vac tC-18 cartridges. The volume of water analyzed was 1500 mL. The PAHs were eluted with ethyl ether, the eluates were evaporated to dryness and the residue was dissolved in methanol. The PAHs were analyzed on a Hypersil Green PAH column and a program of nine excitation and emission wavelength pairs were used. A mobile phase gradient of acetonitrile-water was used. It is possible to detect all the individual PAHs at very high sensitivity, at levels of ng/L. Recoveries were 60–96% for 12 PAHs at concentration levels of 2.33–48.7 ng/L with relative standard deviations in the range 0.4–10% (n=4). The method was applied to determine PAHs in tap-water and reservoir-water samples.

ISSN:1082-6076    

DOI:10.1080/10826079608015813

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Hepatic cholesterol 7α-hydroxylase (CH7OH) is the first and rate-determining enzyme for the biosynthesis of bile acids from free cholesterol in the liver cells. It is important in the cholesterol metabolism, and in the formation of cholesterol gallstones in humans. A rapid reversed phase high performance liquid chromatographic (HPLC) procedure for the measurement of hepatic CH7OH was modified from an HPLC-spectrophotometric method (Chiang, J.Y.L., Meth. Enzymol., 206: 483–91,1991) and validated. A shorter column, a one-component mobile phase (100% acetonitrile), a higher flow rate, and a filter UV detector equipped with 254 nm wavelength were used in this modified procedure. The peaks of reaction products of 20α-, 7α- and 7β-hydroxycholesterol were resolved at baseline with retention times of 9, 10, and 11 min respectively. 20α-hydroxycholesterol was used as internal standard. A peak due to reaction product of 7α-hydroxycholesterol was validated by retention time and spiked test. The linearity of the reaction product of 7α-hydroxycholesterol is up to at least 1250 pmole. Compared to the original procedure, this modified procedure is simpler (single vs binary component mobile phase), faster (22 vs 30 min of running time), and it does not require a variable wavelength UV detector, and it still retains the advantages of the original procedure.

ISSN:1082-6076    

DOI:10.1080/10826079608015814

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Of the twenty-two sulphonamides and three commonly used dihydrofolate reductase inhibitors investigated for reverse phase separation in previous studies, the recoveries of five representative drugs from the stationary phase have been examined. Sulphanilamide, sulfisomindine, sulphaquinoxaline, diaveridine and pyrimethamine were chosen. Peak areas off the analytical column were compared with those obtained by substitution with stainless steel tubing. After careful correction for flow rate differences where necessary, 100% recoveries were indicated. As a further check, Maloprim tablets were assayed for pyrimethamine and the analysed results were found to be (99.1 ± 2.9)%. Limits of detection (LOD) for aqueous standards varied from 0.67 (for sulphanilic acid) - 0.03 μg ml/−1(diaveridine). The linear dynamic range extended from the LOD for each drug to <5 μg mL−1.

ISSN:1082-6076    

DOI:10.1080/10826079608015815

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The influence of different parameters (mobile phase composition - pH, organic solvent, salt nature and concentration; flow rate, injected amount and temperature) on enantiomeric separation of three pharmacologically important compounds (ephedrine, methamphetamine and selegiline) was studied using β-cyclodextrin stationary phase.

ISSN:1082-6076    

DOI:10.1080/10826079608015816

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

In this study, the dispersion coefficients of acetonitrile, ascorbic acid, patulin, 5-hydroxymethylfurfural, 2,4-dichlorophenoxy- acetic acid, 4-chlorophenoxyacetic acid and β-naphtoxyacetic acid are determined by using the stimulus-response technique. The system was pulse stimulated with 10 μL of each tracer with definite concentrations at the flow rate of 1 mL/min. The resulting chromatograms, so called response “C” curves, were obtained for each tracer, individually. The Peclet numbers of each tracer were calculated and evaluated to get dispersion coefficients. The relative dispersion coefficients, based upon the non interacting tracer Acetonitrile (D: 1.83 × 10−6cm/s), were calculated as follows; acetonitrile: 1.00, ascorbic acid: 3.72, patulin: 1.34, 5-hydroxymethylfurfural: 1.68, 2,4-dichloro-phenoxyacetic acid: 2.32, 4-chlorophenoxyacetic acid: 3.23 and β-naphtoxyacetic acid, 2.70.

ISSN:1082-6076    

DOI:10.1080/10826079608015817

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A rapid, specific and reliable high performance liquid chromatographic assay of bromocriptine mesylate in tablets has been developed. Reverse phase chromatography was conducted using a mobile phase of 0.05 M ammonium acetate and acetonitrile, (40% v/v) pH 5.6 and detection at 240 nm. The % recovery and coefficient of variation from six placebo tablets containing 2.5 mg of bromocriptine mesylate were 100.65 and 0.456 respectively. Replicate regression analyses of three standard plots in the concentration range 0.5 - 10 mcg/mL obtained on three different days gave a correlation coefficient <0.9997 and the coefficient of variation of the slopes <0.1%. The assay was precise within day and between days as indicated by ANOVA test. The percentage recoveries from 10 replicate tablets of two commercial brands was 99.4 and 102.8% of the label amount and their coefficients of variation were 1.51 and 1.07%.

ISSN:1082-6076    

DOI:10.1080/10826079608015818

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor