A method is described for the identification and the quantitative determination of the triphenylmethane dyes, malachite green (MG), crystal violet (CV), brilliant green (BG) and leuco malachite green (LMG) and leuco crystal violet (LCV). The analytes were isolated from the matrix by liquid-liquid extraction with acetonitrile. Determination was performed using LC-MS/MS with positive electrospray ionisation. 4 different deuterated internal standards were introduced to improve the quantitative performance of the method. The method has been validated in line with the EU criteria of Commission Decision 2002/657/EC in accordance with the minimum required performance limit (MRPL) set at 2 μgkg(-1) for the sum of MG and LMG. For all the monitored compounds, accuracy, intra-day and inter-day precision were determined at each level of fortification (0.5, 0.75, 1.0 and 2.0 μgkg(-1)). Decision limits CCα and detection capabilities CCβ were calculated according to the standard ISO 11843-2. A study on the applicability of the method was conducted on various aquacultured species with the aim to assess the matrix effects. The presence of residues of leuco brilliant green in fish has also been confirmed from experimental study performed on trout treated with brilliant green, using LTQ-Orbitrap mass spectrometer.
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