Rapid and highly sensitive analysis of ethoxyquin residues in shrimp using ultra performance liquid chromatography-tandem mass spectrometry

A rapid, sensitive method for quantitative and qualitative analysis was developed for the determination of ethoxyquin residues in shrimp. The method involved a new sample preparation process based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) methodology. Ethoxyquin was extracted from homogenized samples with optimized condition using 2% acetic acid in acetonitrile, followed by a cleanup step of dispersive solid-phase extraction using 50 mg of primary secondary amine and 10 mg of graphitized carbon black and then dilution of an extract with acetonitrile: water (80:20). The detection of ethoxyquin was achieved by ultra performance liquid chromatography–tandem mass spectrometry within 2 min retention using positive electrospray ionization mode. The validation method has been performed according to guideline of pesticide residues analysis in food and feed NO.SANCO/10684/2009. Good performance data were obtained with recovery of ethoxyquin from the spiked shrimp samples at 1.5–50.0 µg/kg equal to 82-92% and relative standard deviations were in acceptable range (<6.2%) when compared with the value from Horwitz equation. Good linear calibration in the range of 0.8–64 µg/kg was yielded with coefficient of determination above 0.995. The limit of detection was 0.45 µg/kg. The optimized method has been successfully applied to real shrimp sample which can be detected ethoxyquin in a range of 1.5-350 µg/kg from local fresh markets and super markets, Bangkok, Thailand and the shrimp farm for export in Thailand. The method can also be employed for shrimp analysis in routine laboratory with high sample throughput.