[Simultaneous determination of residues of malachite green, crystal violet and their leuco metabolites in aquatic products by liquid chromatography-tandem mass spectrometry].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of the residues of malachite green (MG), eucomalachite green (LMG), crystal violet (CV) and leucocrystal violet (LCV) in aquatic products. The target analytes were extracted from homogenized samples with a mixture of acetonitrile and ammonium acetate buffer, partitioned against methylene chloride, and purified on tandem neutral alumina and PRS solid-phase extraction (SPE) cartridges. Chromatographic separation was achieved by using a ZORBAX SB-C18 column with an isocratic mobile phase consisting of ammonium acetate (0.5 mmol/L) and acetonitrile (10: 90, v/v) without on-line post-column oxidation with PbO2 which had been widely used in the previous methods. Identification and quantification were performed using multiple reaction monitoring (MRM) with one precursor ion, and two product ions for each analyte and electrospray ionization in positive mode. The limits of detection were 0.5 ng/g. The recoveries were in the range of 77.6% - 98.1%, and the relative standard deviations were less than 8.2%. The results showed that the method is suitable for the determination of residues of MG, LMG, CV and LCV in aquatic products.