Determination of malachite green residues in farmed rainbow trout in Iran

This study was carried out to determine the residues of malachite green (MG) in rainbow trout muscle samples (n = 144) obtained from trout farms in Iran. A high-performance liquid chromatography method with visible detection at 618 nm has been developed to determine the sum of MG and leucomalachite green (LMG) in the muscle samples. This method is based on in situ oxidation of colorless LMG to chromic MG with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. The method was validated according to the criteria described in Commission Decision 2002/657/EC. The recoveries for MG and LMG in spiked muscle samples were higher than 70%; and the relative standard deviations were lower than 9.9% for repeatability and 11.5% for within-laboratory reproducibility. The values of decision limit (CCα) and detection capability (CCβ) for MG were 0.16 μg/kg and 0.39 μg/kg, respectively, which are below the minimum required performance limit (MRPL) of 2 μg/kg for sum of MG and LMG. The residues of MG were detected in 48.6% of the rainbow trout muscle samples, ranging between 0.30 and 146.1 μg/kg. Most of the contaminated samples contained MG at the level of 2-10 μg/kg. The results indicated that application of MG in such a level in trout farms could be a potential hazard for public health. Further investigations should be carried out to determine the residues of MG in other farmed fish species in Iran.