DETERMINATION OF MALACHITE GREEN RESIDUES IN THE EGGS, FRY, AND ADULTMUSCLE-TISSUE OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Malachite green, an effective antifungal therapeutant used in fish cul ture, is a known teratogen. We developed a method to simultaneously de tect both the chromatic and leuco forms of malachite green residues in the eggs, fry, and adult muscle tissue of rainbow trout (Oncorhynchus mykiss). Homogenates of these tissues were fortified with [C-14] mala chite green chloride and extracted with 1% (v/v) acetic acid in aceton itrile or in methanol. The extracts were partitioned with chloroform, dried, redissolved in mobile phase, and analyzed by liquid chromatogra phy (LC) with postcolumn oxidation of leuco malachite green to the chr omatic form. LC fractions were collected every 30 s for quantitation b y scintillation counting. Recoveries of total [C-14] malachite green c hloride residue were 85 and 98% in eggs fortified with labeled malachi te green at concentrations of 0.5 and 1.00 mug/g, respectively; 68% in fry similarly fortified at a concentration of 0.65 mug/g; and 66% in muscle homogenate similarly fortified at a level of 1.00 mug/g. The me thod was tested under operational conditions by exposing adult rainbow trout to 1.00 mg/L [C-14] malachite green chloride bath for 1 h. Musc le samples analyzed by sample oxidation and scintillation counting con tained 1.3 and 0.5 mug/g total malachite green chloride residues immed iately after exposure and after a 5-day withdrawal period, respectivel y.