DETERMINATION OF MALACHITE GREEN AND ITS METABOLITE, LEUCOMALACHITE GREEN, IN CATFISH (ICTALURUS-PUNCTATUS) TISSUE BY LIQUID-CHROMATOGRAPHYWITH VISIBLE DETECTION

To determine residues of malachite green (MG) and its metabolite, leuc omalachite green (LMG), in catfish tissue, analytes are extracted with acetonitrile-buffer and the extract is partitioned into methylene chl oride, Final cleanup and isolation are performed on neutral alumina so lid-phase extraction (SPE) and propylsulfonic acid cation-exchange SPE columns before analysis by liquid chromatography with visible detecti on, PbO2 postcolumn oxidation is performed by isocratic elution with a buffered mobile phase from a cyano column, Recoveries and relative st andard deviations (RSDs) from fortified catfish tissues were 72.9% (RS D, 1.92%; 23 ppb), 75.5% (RSD, 6.85%; 11 ppb), and 69.6% (RSD, 6.93%; 5.7 ppb) for MG and 87.4% (RSD, 2.92%; 21 ppb), 88.1% (RSD, 5.94%; 10 ppb), and 82.6% (RSD, 11.5%; 5.3 ppb) for LMG,The method was applied t o MG-incurred catfish at depuration times of 0, 2, 4, 8, and 24 h, Ave rage levels of residual MG and LMG in the 24 h depuration catfish tiss ue were 73.4 and 289 ppb, respectively.