Confirmatory analysis of malachite green, leucomalachite green, crystal violet and leucocrystal violet in salmon by liquid chromatography-tandem mass spectrometry

A method has been developed to analyse for malachite green (MG), leucomalachite green (LMG), crystal violet (CV) and leucocrystal violet (LCV) residues in salmon. Salmon samples were extracted with acetonitrile:McIIIvain pH 3 buffer (90:10 v/v), sample extracts were purified on a Bakerbond strong cation exchange solid phase extraction cartridge. Aliquots of the extracts were analysed by LC-MS/MS. The method was validated in salmon, according to the criteria defined in Commission Decision 2002/657/EC. The decision limit (CCalpha) was 0.17, 0.15, 0.35 and 0.17 microg kg(-1), respectively, for MG, LMG, CV and LCV and for the detection capability (CCbeta) values of 0.30, 0.35, 0.80 and 0.32 microg kg(-1), respectively, were obtained. Fortifying salmon samples (n=6) in three separate assays, show the accuracy to be between 77 and 113% for MG, LMG, LCV and CV. The precision of the method, expressed as RSD values for the within-laboratory reproducibility, for MG, LMG and LCV at the three levels of fortification (1, 1.5 and 2.0 microg kg(-1)), was less than 13%. For CV a more variable precision was obtained, with RSD values ranging between 20 and 25%.