POSTCOLUMN ELECTROCHEMICAL OXIDATION OF LEUCO MALACHITE GREEN FOR THEANALYSIS OF RAINBOW-TROUT FLESH USING HPLC WITH ABSORBENCY DETECTION

Malachite green is a dye used in aquaculture as a parasiticide. A meth od is described for the quantitation of residues of malachite green an d its colourless reduced form, leuco malachite green, in the flesh of rainbow trout. The analytes are extracted with solvent and purified us ing a C-18 solid phase extraction cartridge. Determination of both com pounds by reversed phase HPLC with absorbance detection at 610 nm is a chieved following post-column oxidation of the leuco form to malachite green using an electrochemical detector cell. The limits of detection for malachite green and leuco malachite are 6 ng/g and 3 ng/g, respec tively. At concentrations from 25-200 ng/g, recoveries in the range 73 -87% were achieved for malachite green and 89-98% for leuco malachite green. Oxidation of leuco malachite green using activated charcoal is also described as as an alternate manner of determining total malachit e green.