A high-throughput gas chromatography-mass spectrometry method was established for the analysis of 54 pesticide residues in milk. Samples were extracted with acetonitrile while shaking, and the extract was concentrated and purified using solid-phase extraction (SPE) on a C18 column using acetonitrile as the eluent. The external standard method was used for quantification. The results showed that good linearity was observed over the concentration range from 0 to 1.00 μg/mL, with correlation coefficient (R2) greater than 0.990. Recoveries were between 43.33% and 113.87% with a relative standard deviation (RSD) of 1.8%–19.8% (n = 6). This method is accurate, simple and suitable for large numbers of milk samples.

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.

A gas chromatography-mass spectrometry (GC-MS) method was developed for the determination of quinoxyfen in milk. The sample was extracted with acetronitrile, and then the extract was cleaned up by dispersive solid-phase extraction (dSPE) with C18 and N-propyl ethylenediamine (PSA) as sorbent materials. The analyte was separate on an Agilent HP- 5MS column, detected by GC-MS, and quantified by matrix-matched external standard method. The results showed that good linearity was obtained within the concentration range of 0.00–1.00 μg/mL with a correlation coefficients (R2) > 0.998 7. The average recoveries at three spiked levels (5, 10 and 20 μg/kg) ranged from 83.2% to 100.8% with relative standard deviations (RSDs) of 2.1%–4.3%. The limit of quantitation was 5 μg/kg. The proposed method was simple, sensitive and reliable, and could be applied to the determination of quinoxyfen in milk. The content of quinoxyfen in milk samples from 75 dairy households was detected to be less than the national limit value by this method.