A rapid and simple method for simultaneous determination of triphenylmethane dye residues in rainbow trouts by liquid chromatography-tandem mass spectrometry

A rapid and simple LC-MS/MS method was developed and optimized for screening and confirmation of triphenylmethane dyes including malachite green (MG), leucomalachite green (LMG), crystal violet (CV), leucocrystal violet (LCV) and brilliant green (BG) in fish muscle with skin. Leucocrystal violet D6 (LCV-D6) and leucomalachite green-D5 (LMG D5) was used as internal standards. Sample preparation is a simple procedure based on solid-liquid extraction with acetonitrile containing 1% acetic acid, followed by centrifugation and evaporation of the supernatant. The residue was dissolved in acetonitrile with 0.1% acetic acid and centrifuged prior to LC-MS/MS analysis. Chromatographic separation of analytes was performed on an Inertsil ODS-4 C18 column with ammonium acetate buffer in acetonitrile gradient. The mass detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI+). The developed method was validated according to the criteria set in Commission Decision 2002/657/EC. The decision limit (CCα) was 0.43, 0.24, 0.33, 0.28 and 0.17 μg kg−1 for MG, LMG, CV, LCV and BG respectively. The detection capability (CCβ) values obtained were 0.56, 0.31, 0.43, 0.37 and 0.22 μg kg−1, respectively. The precision of the method, expressed as relative standard deviation (RSD) values for the within-day and inter-day laboratory reproducibility, for MG, LMG, CV, LCV and BG at the four levels of fortification (0.3, 0.5, 1, and 2 μg kg−1), was less than 16 and 19% respectively. Accuracy of the method was confirmed by successful participation of a proficiency test organized by FAPAS. The method has been used for the analysis of 208 fish samples of which seven samples were found to be non-compliant containing low residues of LMG and LCV.