Determination of the amide herbicides in milk using dispersive liquid-liquid microextraction prior to GC-MS

Objective To supervise the food safety problem in milk and achieve a rapid and accurate determination of pesticide residues in milk.

Method In this paper, a simple, sensitive and environment friendly dispersive liquid-liquid microextraction (DLLME) technique coupled with gas chromatography-mass spectrometry (GC-MS) was established for the extraction and determination of four amide herbicides (alachlor, acetochlor, pretilachlor, and metolachlor) in milk samples.

Result and conclusion The factors that affected extraction efficiency were studied and optimized. Eventually, 40 μL carbon tetrachloride was used as the extractant, 1 000 μL methanol was chosen as the dispersant and the extraction time was set to 1.0 min. Under the optimum conditions, the good linearity was exhibited from 0.05 to 5.00 mg·L^-1 herbicide, with the correlation coefficient being more than 0.997 8. The method had a high sensitivity, and the limits of detection (S/N=3) of the four amide herbicides ranged from 0.8 to 1.4 μg·L^-1. The recoveries of the target analytes from milk samples were found between 67.0% and 105.7%, and the relative standard deviations (RSD) varied from 1.6% to 8.3%. The method can be successfully applied for the analysis of amide herbicides in real milk samples.