EVALUATION OF O-PHTHALALDEHYDE AS BIFUNCTIONAL FLUOROGENIC POSTCOLUMN REAGENT FOR GLUTATHIONE IN LC

A method for the assay of various forms of glutathione in human plasma has been developed. The reduced form was measured after direct injection of deproteinized plasma with perchloric acid. The unbound oxidized forms were assayed in deproteinized plasma after reduction with dithiothreitol. The total amount of glutathione was determined by reduction before protein precipitation. Separation of reduced glutathione from other endogenous thiols was by ion-pair, reversed-phase, high-performance liquid chromatography. Post-column derivatization with ortho-phthalaldehyde made the assay more selective than when using pyrenemaleimide as thiol fluorogepic reagent. The linear range was 0.02 to 2.0 mug mL-1 with good repeatability (relative standard deviation less than 5 % for the lowest concentration measured).