In this paper, a high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was proposed to simultaneously detect multiple pesticide residues in milk. The sample was extracted with acetonitrile, and partitioned by adding sodium chloride and magnesium sulfate. The extraction was carried out twice, and then the extract was purified with a C18 solid phase extraction column. Finally, the eluate was collected and evaporated to dryness after rotary evaporation, and the resulting residue was redissolved prior to instrumental analysis. The chromatographic separation was performed on a C18 column using gradient elution with a mobile phase consisting of 5 mmol/L ammonium acetate (containing 0.1% formic acid) and methanol. The detection was conducted using an electrospray ionization source under the multireaction monitoring (MRM) mode. The results showed that the calibration curves for acetamiprid, aldicarb, clothianidin, methamidophos, novaluron, fenbutatin-oxide, spirodiclofen, difenoconazole, cycloxydim, metaflumizone and 2-methyl- 4-chloro-phenoxyacetic acid (MCPA) had a good linearity in the concentration range of 0–100 ng/mL with correlation coefficients (R2) all greater than 0.995 0. The average recoveries for blank milk samples at three spiked concentration levels (1, 2 and 4 μg/L) were 40.2%–99.2%, with relative standard deviation (RSD) less than 18.9%, and the detection limit of the method was 1.00 μg/L. This method could allow quick and sensitive analysis of the contents of 11 pesticide residues in milk.

This study established a method for the simultaneous detection of 19 β-agonist veterinary drug residues in milk samples. The samples were extracted with acidified acetonitrile solution, and the phospholipids were removed by using an Oasis PRiME HLB solid-phase extraction cartridge. The analytes were detected by ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Under optimized pretreatment and instrumental conditions, all analytes showed a good linear relationship in the concentration range of 0 to 10 ng/mL (R2 ≥ 0.995). The average recovery rates for milk samples spiked at levels of 0.2 to 1.0 μg/kg were between 70% and 110%, and the precision relative standard deviation (RSD) was less than 15%. The method had the advantages of simple and fast pretreatment, and high sensitivity and stability, and therefore could be used for the rapid detection of β-agonist veterinary drug residues in milk.