HPLC DETERMINATION OF GLUTATHIONE AND L-CYSTEINE IN PHARMACEUTICALS AFTER DERIVATIZATION WITH ETHACRYNIC-ACID

Ethacrynic acid and its methyl ester are proposed as useful pre-chroma tographic derivatization reagents for the HPLC analysis (UV detection) of reduced glutathione (GSH) and L-Cysteine. The optimum experimental conditions for the thiol derivatization, the removal of the excess re agent by liquid-liquid or solid-phase extraction and the reversed-phas e chromatographic separations of the thiol adducts were investigated. The method was applied to the HPLC determination of GSH and L-cysteine in commercial formulations and proved to be suitable for the HPLC det ermination of oxidized glutathione (GSSG) after reduction to GSH using dithiothreitol (DTT).