Automatic magnetic solid phase extraction for rapid and high-throughput determination of neonicotinoid insecticides and their metabolites in serum, breast milk and urine samples.

In this study, an automatic magnetic solid phase extraction method was developed to determine six parent neonicotinoids (NEOs) and three of their metabolites in breast milk, serum and urine samples. As key extraction parameters, the sorbent amount, washing solvent and elution solvent were optimized to 4 mg of HLB packing magnetic sorbent, pure water and acetonitrile, respectively. Recoveries of the analytes ranged between 81% and 121% for bovine milk samples, 64% and 122% for fetal bovine serum samples and 81% and 109% for pooled urine samples, with RSDs of <20%. The intra-day and inter-day variations were 2.7-14.9% and 1.2-13.4%, respectively, for all analytes in the three matrices. The limit of quantitation ranged from 0.002-0.05 ng mL-1, 0.002-0.06 ng mL-1 and 0.012-0.348 ng mL-1 for the target compounds in bovine milk, fetal bovine serum and pooled urine samples, respectively. The validated method was successfully applied for biomonitoring of NEOs in real samples. Notably, the developed method required only 200 μL of sample and 1.4 mL of organic solvent to prepare a batch of 32 samples in less than 30 min, making it suitable for large-scale epidemiological biomonitoring of human exposure to NEOs or equivalent agrochemicals.