Objective: A method for the determination of 80 pesticide residues in milk by liquid chromatography-time-of-flight mass spectrometry(LC-QTof-MS) was developed.
Methods: The target compounds in milk were extracted with acetonitrile-methanol(9∶1, V/V) containing 1% acetic acid, and purified by aminated multi-walled carbon nanotubes(NH_2-MWNTs). The chromatographic column was Waters Acquity UPLC BEH C_(18 )(100 mm×2.1 mm, 1.7 μm). The 80 pesticides were detected by liquid chromatography-time-of-flight mass spectrometry and quantified using an external standard method by matrix matched calibration curve.
Results: The purification method showed a good linearity(r~2≥ 0.99) over the concentration range from 5 to 100 μg/L for the 80 pesticides in this study. The limits of detection(LODs) and quantification(LOQs) of the 80 pesticides in milk ranged from 0.01 to 0.50 μg/L and 0.03 to 1.50 μg/L, respectively. The mean recoveries of the three spiked levels ranged from 71.5% to 116.9% with the relative standard deviation ranging from 1.2% to 18.1%, indicating that the accuracy and precision of the method were good. Among the milk samples, no residues of the 80 pesticides in this study were found after screening.
Conclusion: The method has good linearity, good sensitivity, accuracy and precision and is suitable for the simultaneous and rapid determination of 80 pesticide residues in milk.
Keywords: NH_2-multi walled carbon nanotube; liquid chromatography-time-of-flight mass spectrometry; milk; pesticide residue.