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T M Jefferies

Publications and source records attributed to T M Jefferies.

32 records · Page 2Linked to original sources
PubMed1983

An investigation of high-performance liquid chromatographic methods for the analysis of amphetamines.

Three pre-column derivatization reagents, namely o-phthalaldehyde, 4-chloro-7-nitro-benz-2,1,3-oxadiazole, sodium naphthaquinone-4-sulphonate and two ion-pair reagents, namely, naphthalene-2-sulphonate and sodium dodecylsulphate have been investigated for their suitability for the qualitative and quantitative analysis of urine and plasma samples containing amphetamines. The derivatization method employing sodium naphthaquinone-4-sulphonate was found to be selective and sufficiently sensitive for the routine determination of amphetamine and methylamphetamine in urine and plasma samples at the ng/ml level.

Adult↗
PubMed1983

The determination of D-penicillamine and its disulphide in plasma by reversed-phase ion-pair high-performance liquid chromatography.

Reversed-phase ion-pair conditions are used for the determination of D-penicillamine and penicillamine disulphide. Two chromatographic systems were employed, one for penicillamine and the other for penicillamine disulphide. The procedures permit the determination of total penicillamine (protein-bound, free and as disulphides) in whole plasma, and total penicillamine (free and as disulphides) in plasma ultrafiltrate, using an incubation step in the presence of dithiothreitol. Free penicillamine and penicillamine disulphide may be determined independently by direct injection of plasma ultrafiltrate. Both solutes may be measured at an on-column sensitivity of 10 ng, utilizing an electrochemical detector based on a glassy carbon electrode.

Journal Article↗
PubMed1979

Ion-pair high-performance liquid chromatography: the use of low concentrations of long-chain alkylbenzyldimethylammonium chlorides for resolving anionic solutes.

The qualitative and quantitative determination of large anionic solutes, including the drug sodium cromoglycate, by an ion-pair high-performance liquid chromatographic technique using alkylbenzyldimethylammonium chlorides as pairing ions is described. The method provides a sensitive and selective assay for the solutes examined in both simple aqueous solutions and in complex biological fluids, and requires no pre-extraction step. Retention mechanisms are discussed.

Anions↗
PubMed1979

Surfactant ion-pair high-performance liquid chromatography of tryptophan and some of its metabolites in biological fluids.

A rapid, sensitive assay for tryptophan and some of its metabolites in urine, plasma and saliva has been developed using sodium dodecylsulphate as a pairing ion in a surfactant ion-pair high-performance liquid chromatography technique. The method is highly selective for tryptophan which is separated from its main indoleamine metabolites, 5-hydroxytryptophan, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid, and from kynurenine. The usefulness of the assay has been demonstrated in plasma level and urinary excretion studies of orally administered tryptophan.

Biological Availability↗
PubMedDate not supplied

Analysis of cocaine, benzoylecgonine, ecgonine methyl ester, ethylcocaine and norcocaine in human urine using HPLC with post-column ion-pair extraction and fluorescence detection.

The measurement of cocaine and its major metabolites has been achieved by an HPLC method that compensates for their different solubilities and detection properties. Although ecgonine methyl ester is a major metabolite it is generally not measured by HPLC because it is poorly detectable by UV, and its water solubility makes recovery from urine difficult. Using modified solid-phase extraction procedures recoveries of 85% for ecgonine methyl ester, 97% for cocaine, 106% for benzoylecgonine and 80% for ethylcocaine have been obtained from urine. Increased chromatographic retention and detection sensitivity has been obtained by formation of the t-butyldimethylsilyl derivative of ecgonine methyl ester which was found to be stable in the HPLC mobile phase for at least 1 week. Alkylation of norcocaine and benzoylecgonine has improved their detection sensitivity and also chromatographic resolution. All calibrations were linear over the range 200-1000 ng ml-1 in urine with correlation coefficients > 0.99.

Chromatography, High Pressure Liquid↗