A new and versatile method for determination of thiolamines of biological importance

A method for the separation and quantitation of several important biologica l thiolamines is described. The procedure employs a C-18 reversed-phase HPL C system to separate the dinitrophenyl derivatives of reduced and oxidized glutathione and cysteine and relies on an internal standard, N-epsilon-meth yllysine, to minimize experimental error. The method was validated in three matrices (water, HepG2 cell lysates, and mouse liver homogenates) using se veral criteria. The detector response was linear for the dinitrophenyl deri vatives of glutathione, glutathione disulfide, cysteine, and cystine in the concentrations ranging from 10 to 50 nmol/ml. Inter- and intra-day variati on, percent recovery in the biological matrices, and limits of detection an d quantitation were determined. For the most accurate determination, it is essential that standard curves be produced daily and in the same matrix as that being analyzed. (C) 2001 Elsevier Science BM All rights reserved.