Effectiveness of different cleanup sorbents for the determination of avermectins in fish by liquid chromatography tandem mass spectrometry.

An effectiveness and comparative study of cleanup sorbents used in dispersive solid phase extraction (DSPE) for the determination of avermectins, including emamectin (EMA), abamectin (ABA), doramectin (DOR), moxidectin (MOX), and ivermectin (IVE), was performed. Three different types of cleanup sorbents, alumina (Al), primary and secondary amine (PSA) and octadecyl (C18), were used to remove the matrix interference in fish samples. Homogenised fish samples were extracted with acetonitrile, magnesium sulphate anhydrous and sodium chloride. The cleanup sorbents were separately applied to the supernatant during the DSPE procedure; the mixtures were shaken and centrifuged, and the supernatant was dried. The extracts were reconstituted with acetonitrile/water and quantified by liquid chromatography tandem mass spectrometry with electrospray ionisation in the positive mode with two product ions that were monitored by selected reaction monitoring. The performance of each cleanup sorbent was observed for its accuracy and precision in a spiked blank sample at a concentration of 5 μg kg−1. The combination of the cleanup sorbents PSA and C18 was found to be the most effective in the cleanup of the fish samples. In the validation tests, the detection limit was in the range of 0.3 μg kg−1 to 0.4 μg kg−1, and the quantitation limit for all avermectins was 1 μg kg−1 in the linearity range of 1–15 μg kg−1. The recoveries of avermectins were 91.9–102.5%, with a relative standard deviation lower than 19%

Comparison of microwave assisted acid digestion methods for ICP-MS determination of total arsenic in fish tissue

Fish is one of the most important sources of arsenic exposure in human diet and the Food Safety and Quality Division, Ministry of Health since 2007 has required routine monitoring of total arsenic in seafoods such as fish. This study describes an improved extraction method of total arsenic in fish using microwave assisted acid digestion procedure before being analysed by inductively coupled plasma mass spectrometry (ICP-MS). The parameters studied were pre-treatment of sample, digestion temperature, time programme and the chemicals (HNO3/H2O2) used. Arsenic contents in fish samples under these conditions were compared using the standards additions technique. Microwave assisted acid digestion method with a combination of ultrapure concentrated nitric acid (HNO3) to concentrated hydrogen peroxide (H2O2) at a ratio of 7 mL: 1 mL, run time of 25 min and digestion temperature of 200°C with no pre-treatment was found to have recovery of 100.7% as compared with other digestion procedure where the recovery were 115.5, 111.6 and 101.8%. Validation using certified reference material (CRM) of fish tissue (DORM-3) showed a recovery of 101.4 ± 2.5% for total arsenic from the CRM