Determination of Acequinocyl and Hydroxyacequinocyl Residues in Food by Ultra-High Performance Liquid Chromatography Separation and Tandem Mass Spectrometric Detection

Abstract

A sensitive method for the quantification of acequinocyl and hydroxyacequinocyl in foodstuff (beef, chicken muscle and liver, fish, peach, cucumber, Chinese cabbage and broad bean) was developed by ultra-high performance liquid chromatography and tandem mass spectrometry. Acequinocyl and hydroxyacequinocyl were found to be stable in the presence of formic acid at low temperature (−18°C) in the dark. The target compounds in solid food samples were successively extracted by acetonitrile containing 0.5 % (v/v) formic acid, and then cleaned up by using Florisil columns, and then evaporated to near dryness under a nitrogen stream at 40°C, and finally dissolved in acetonitrile containing 0.5 % (v/v) formic acid. No matrix effect was observed from any foodstuff. Linear calibration curves with correlation coefficients of 0.9996 for acequinocyl and 0.9998 for hydroxyacequinocyl over the same range 2 to 100 μg L −1 were obtained. The intra-day and inter-day relative standard deviations were both superior to 3 % (N=10) for 5 μg L −1 . The method detection limits were 1.4 μg kg −1 for acequinocyl and 1.3 μg kg −1 for hydroxyacequinocyl. The method quantification limits were 4.6 and 4.3 μg kg −1 , respectively, which were at least five times lower than their maximum residue limits for food. Neither acequinocyl nor hydroxyacequinocyl was detected in any foodstuff. The recoveries at spiked levels of 5, 10, and 50 μg kg −1 varied in the ranges 81-100 % for acequinocyl and 77-103 % for hydroxyacequinocyl in the foodstuffs, validating the accuracy of the proposed method.