Ultrasonic enhancement of leaching and in situ derivatization of haloacetic acids in vegetable foods prior to gas chromatography-electron capture detection

With a new oxidant for post-column chemical derivation, a novel approach was developed for the determination of Malachite Green (MG) and Leucomalachite Green (LMG) in fish by high-performance liquid chromatography (HPLC). A C(8) column was used for separation, and elution was performed with a pH 2.5 phosphate buffer (0.02molL(-1)) containing 40% acetonitrile. When the eluate was combined with 3.0x10(-4)molL(-1) iodine solution, LMG was converted to MG and detected at 618nm after post-column derivatization. The recoveries of MG and LMG were ranged from 67.3% to 73.9% and 84.7% to 92.1%, respectively, which were obtained by measuring the amount of MG and LMG in the samples with solvent calibration curve. The decision limit (CCalpha) and the detection capability (CCbeta) obtained for MG and LMG were in the range of 0.10-0.17 and 0.13-0.23mugkg(-1) in grass carp, shrimp and shellfish. This method appeared suitable for the control of MG and LMG residues in aquatic products.