For the accurate quantitation of glutathione (GSH), cysteine (Cys) and cysteinylglycine (CysGly) in human plasma by detection of fluorescence after derivatization with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD-F), a thiol-specific fluorogenic agent and high-performance liquid chromatography (HPLC) , we attempted to identify optimum conditions for the derivatization and treatment of samples. The extent of derivatization with SBD-F of endogenous thiol compounds in human plasma was

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... affected by several factors, such as the concentration of SBD-F and the reaction time. Acidification and deproteinization of plasma immediately after the separation of plasma from whole blood were essential and prevented the determination of inappropriately low val-ues. The method developed in the present study allowed recovery that was closed to 100% for each compound. The mean values determined for 61 healthy individuals were as follows: Cys, 50.1 M; CysGly, 12.2 M; and GSH, 5.3 M.