[Determination of 80 pesticide residues in milk using NH_2-MWNTs by liquid chromatography-time of flight mass spectrometry].

Abstract

A method for the determination of 80 pesticide residues in milk by liquid chromatography-time-of-flight mass spectrometry(LC-QTof-MS) was developed. 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. 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. 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.