Determination of a new naphthoquinone derivative, NQ12, in human plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the dete rmination of a new phospholipase A(2) inhibitor, NQ12, in human plasma and urine. The sample preparation was simple: 2 volumes of acetonitrile were ad ded to the biological samples to deproteinize it. A 50-mu l aliquot of the supernatant was injected onto a C-18 reversed-phase column. The mobile phas e employed was 0.05M acetate buffer (pH 3) : acetonitrile : methanol (30:45 :25, v/v/v) and run at a flow rate of 1.5 ml/min. The column effluent was m onitored by a UV detector set at 298 nm. The retention times for NQ12 and t he internal standard were approximately 5.5 and 7.0 min, respectively. The detection limits for NQ12 in human plasma and urine were all 20 ng/ml. The coefficients of variation of the assay (within-day and between-day) were ge nerally low (below 11.8%) for human plasma and urine. No interferences from endogenous substances were found.