OPTIMIZATION OF A LIQUID-CHROMATOGRAPHIC METHOD FOR DETERMINATION OF MALACHITE GREEN AND ITS METABOLITES IN FISH-TISSUES

A liquid chromatographic (LC) method was adapted and optimized for the determination of malachite green and its metabolites in fish plasma a nd muscle, Residues in plasma were extracted with acetonitrile, the ex tract was evaporated to dryness, and residues were resolubilized for L C analysis, Residues in muscle were extracted with an acetonitrile-ace tate buffer mixture, reextracted with acetonitrile, and partitioned in to methylene chloride with final cleanup on alumina and propylsulfonic acid solid-phase extraction columns, Residue levels were determined b y using an LC cyano column with a PbO2 postcolumn and visible detectio n (618 nm). Overall mean recoveries of parent malachite green (MG-C) a nd its major metabolite, leucomalachite green (MG-L), from plasma were 93 and 87%, respectively, at fortification levels ranging from 25 to 250 ppb, Overall mean recoveries of MG-C and MG-L from muscle were 85 and 95%, respectively, at fortification levels ranging from 5 to 100 p pb, Relative standard deviations (RSDs) of recoveries at all fortifica tion levels ranged from 3.9 to 7.0% for plasma and from 2.1 to 5.2% fo r muscle, The method was applied to incurred residues in tissues sampl ed from catfish after waterborne exposure to [C-14]MG-C. Mean recoveri es of total radioactive residues in plasma and muscle throughout the e xtraction and cleanup process were 88 and 87%, respectively, and corre sponding RSDs for MG-C and MG-L were in the same range as those for fo rtified tissues, MG-L, was confirmed as the major metabolite of MG-C i n catfish.