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 column-switching for the determination of ethacrynic acid in urine samples, 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 separation of ethacrynic acid from the biological matrix. Polar urinary compounds are removed by flushing the pre-column with purified water, and the enriched analyte is then switched in back-flush mode onto an HP-LiChrospher RP C18, 5 mu m (125 mm x 4 mm i.d.) analytical column, where it is chromatographed using an acetonitrile-acetate buffer gradient elution. 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 detection was 1 ng/ml, the total analysis time being less than 10 min. The reliability of this study has been tested by analyzing urine samples after minimum single dose (25 mg) administration of ethacrynic acid.