Abstract: A multi-residue method based on high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for the quantitative determination of abamectin, ivermectin and emamectin benzoate in grouper plasma, muscle and liver. The target analytes were extracted with acetonitrile and then cleaned up with an alkaline alumina column/LC-C18 SPE column. The analytes were separated on a Thermo Hypersil Gold C18 column by gradient elution with 0.1% formic acid-10 mmol/L ammonium acetate as mobile phase A and acetonitrile as mobile phase B, and detected by multiple reaction monitoring (MRM) with electrospray ionization (ESI) under positive ion mode. The target compounds were quantified by the matrix-matched external standard method. Both pesticides could move into water through various environmental routes. Therefore, the bioaccumulation and elimination of avermectin and ivermectin in groupers were studied by bath administration at the upper and lower concentration limits (4 and 8?ng/mL for avermectin, and 6 and 12 ng/mL for ivermectin) in environmental water. Meanwhile, the food safety risk of the pesticide residues in fish was assessed. The results showed that the calibration curves were linear (R2 > 0.99) in the concentration range of 2.5–200?ng/mL for abamectin and ivermectin and 0.25–20?ng/mL for emamectin benzoate. The limits of detection (LOD) for abamectin, ivermectin and emamectin benzoate were 2.5, 2.5 and 0.25 ng/mL in plasma, 1, 1 and 0.1 μg/kg in muscle, 2.5, 2.5 and 0.25?μg/kg in liver, respectively. The limits of quantification (LOQ) were 5, 5 and 0.5 ng/mL in plasma, 2, 2 and 0.2 μg/kg in muscle, 5, 5 and 0.5?μg/kg in liver, respectively. The average recoveries at three spiked levels ranged from 74.6% to 93.6%. Intra-day and inter-day relative standard deviations (RSDs) were 2.3%–10.9% and 9.2%–12.6%, respectively. Abamectin and ivermectin were no-bioaccumulative substances and their elimination processes in grouper conformed to a first order kinetics equation. Under the conditions of this study, drug concentration was an important factor affecting the residual drug concentration and elimination time in grouper muscle tissues. Gouper was safe for consumption 22 and 39 days after 72 h bath administration for 4–8?ng/mL abamectin and 6–12 ng/mL ivermectin, respectively.

Key words: grouper, avermectin residues, food safety risk assessment