HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ASSAY FOR N-ACETYLCYSTEINE IN BIOLOGICAL SAMPLES FOLLOWING DERIVATIZATION WITH N-(1-PYRENYL)MALEIMIDE

N-Acetylcysteine is a thiol antioxidant with expanding clinical import ance. A sensitive, rapid method for determining reduced N-acetylcystei ne (NAG) concentration in biological samples has been developed which uses a modified reversed-phase high-performance liquid chromatography (HPLC) technique in conjunction with the derivatising agent N-(1-pyren yl)maleimide (NPM). The NAC-NPM adduct was analysed by HPLC with fluor escence detection. The calibration curve for NAC was linear over the r ange 8-2500 nM and the coefficient of variation obtained for the withi n-run precision and the between-run precision for 0.5 mM NAC was 1.5% and 2.7%, respectively. Relative recovery of NAC from biological mater ials ranged between 86% and 96% and the limit of quantitation from bio logical samples was 32 nM. These results suggest practical advantages relative to other widely-accepted methods of NAC measurement.