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Abstract

A simple, reproducible and sensitive micellar electrokinetic chromatography (MEKC) method was developed for the separation and determination of malachite green (MG), leucomalachite green (LMG), gentian violet (GV) and leucogentian violet (LGV) from catfish and carp. Field-enhanced sample injection with reverse migrating micelles (FESI-RMM) was used for on-line concentration of the analytes. The buffer contained 50 mM H3PO4-NaOH, 140 mM sodium dodecyl sulfate (SDS), 15% acetonitrile and 15% 2-propanol, at the pH of 2.0. The sample solution was diluted with water containing 5 mM SDS and injected for 15 s with -8 kV after injection of 2 s water plug. The effects of concentration of SDS and organic modifier, the sample matrix, the injection time of water plug, the injection voltage and injection time of sample on the separation and stacking efficiency were investigated. Under the optimum conditions, the analytes were well separated and by optimizing the stacking conditions, about 121, 146, 150 and 87 fold improvement in the detection sensitivities were obtained for GV, MG, LMG and LGV, respectively. The instrument detection limits (S/N = 3) of GV, MG, LMG and LGV were 40, 70, 50 and 50 ng/mL, respectively. The recoveries of GV, MG, LMG and LGV in the extracts of catfish were 87.8-96.7%, 87.9-100.2%, 96.7-101.4% and 89.8-94.2%, respectively. The GV, MG, LMG and LGV in spiked (1 μg/mL) catfish and carp extracts were successfully determined with satisfactory repeatability and recovery.

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