Confirmation of malachite green, gentian violet and their leuco analogs in catfish and trout tissue by high-performance liquid chromatography utilizing electrochemistry with ultraviolet-visible diode array detection and fluorescence detection

A sensitive analytical procedure for the confirmation of residues of malachite green (MG), gentian violet (GV) and their leuco analogs (LMG and LGV) in catfish and trout tissue at 10 ng/g is described. Frozen (−20°C) fish fillets were cut into small pieces and homogenized in Waring blendors. The compounds of interest were extracted from 20-g amounts of homogenized fish tissue with acetonitrile-buffer, partitioned against methylene chloride, and isolated with tandem neutral alumina and propylsulfonic acid cation-exchange solid-phase extraction cartridges. Samples of 100 μl (0.8 g equiv.) were chromatographed isocratically in 10 min using an acetonitrile-buffer mobile phase on a short-chain deactivated (SCD) reversed-phase column (150×4.6 mm I.D.) in-line with a post-column oxidation coulometric electrochemical cell (EC), a UV-Vis diode array detector and a fluorescence detector.