Assays for total homocysteine and other thiols by capillary electrophoresis-laser-induced fluorescence detection I. Preanalytical condition studies

In recent papers, we presented a new analytical method for thiol quantifica tion in serum. It is based on the use of capillary electrophoresis and lase r-induced fluorescence to analyze thiol 6-iodoacetamidofluoresceine (IAF) d erivatives. Quantitative results of homocysteine, glutathione, cysteine-gly cin, and cysteine were shown (Clin. Chem. 45 (1999) 412). A comprehensive c omparison of the quantitation of homocysteine in serum, using high-performa nce liquid chromatography/conventional fluorescence detection and fluoresce nce polarization immunoassay was also used (E. Causse et al., Electrophores is 21 (2000) 2074). Sample preparation prior to derivatization with IAF had never been investigated. In this work we present the results of quantitati on of thiols in serum and plasma with three different anticoagulants widely used: ethylenediaminetetraacetic acid (EDTA), heparin, and sodium citrate. We show that serum and EDTA plasma gave the same results. Then serum prote in precipitations by acetonitrile, acetone, sulfosalicylic acid, perchloric acid and trichloracetic acid, prior to derivatization by IAF, were also in vestigated. Their influence on the concentrations of the thiols were determ ined. Sulfosalicylic acid and acetonitrile precipitations are well adapted, whereas acetone cannot be used. (C) 2000 Elsevier Science B.V. All rights reserved.