ONLINE TRACE ENRICHMENT FOR THE DETERMINATION OF ETHACRYNIC-ACID IN URINE BY LIQUID-CHROMATOGRAPHY AND COLUMN-SWITCHING

A chromatographic method based on liquid chromatography (LC) using col umn-switching for the determination of ethacrynic acid in urine sample s, is described. The proposed system uses an Hypersil ODS-C18, 30 mu m (20 mm x 2.1 mm i.d.) pre-column for the pre-concentration and separa tion of ethacrynic acid from the biological matrix. Polar urinary comp ounds are removed by flushing the pre-column with purified water, and the enriched analyte is then switched in back-flush mode onto an HP-Li Chrospher RP C18, 5 mu m (125 mm x 4 mm i.d.) analytical column, where it is chromatographed using an acetonitrile-acetate buffer gradient e lution. The UV detector was set at 275 nm. The recovery of drug was 99 +/- 2% in the 0.010-1.0 mu g/ml concentration range. The limit of det ection was 1 ng/ml, the total analysis time being less than 10 min. Th e reliability of this study has been tested by analyzing urine samples after minimum single dose (25 mg) administration of ethacrynic acid.