Screening and confirmation of triphenylmethane dyes and their leuco metabolites in trout muscle using HPLC-vis and ESP-LC-MS

An extraction and clean-up protocol for the determination of Malachite Gree n and Crystal Violet and the corresponding leuco compounds in trout muscle has been developed. Final determination is by HPLC with visible (screening) or ESP-MS (confirmation) detection. In both cases lead(IV) oxide was used on-line to oxidise the leuco compounds back to the parent after chromatogra phic separation and prior to detection. The procedure was validated down to 2 mu g kg(-1). Intra- and inter-batch precision was measured at 3 levels f or all compounds. Recoveries were in the range 66-116% with RSD of 1-17% fo r determination by HPLC with visible detection. For LC-MS determination, re coveries were in the range 61-94% with RSD of 4-15%. Limited surveillance d ata indicated that Malachite Green usage was more effectively monitored by including the leuco compound as well as the parent (9 positives for the leu co compound as opposed to 1 for Malachite Green out of 31 samples analysed) .