Analysis of 7 Dinitroaniline Residues in Complex Food Matrices by GC–NCI/MS

A modified quick, easy, cheap, effective, rugged, and safe sample preparation method combined with gas chromatography–negative chemical ionization–mass spectrometry (GC–NCI/MS) has been developed for the determination of 7 dinitroaniline herbicide residues in complex matrices (garlic, olive oil, scallion, leek and chili). Dinitroaniline residues were extracted with hexane-saturated acetonitrile. After the cleanup with the dispersive solid-phase extraction, the extract was analyzed by GC–NCI/MS in selected ion monitoring mode. Two isotope internal standards (trifluralin-d 14 and pendimethalin-d 5) were employed for quantification. Compared with electron ionization (EI) mode, the superiorities of NCI in sensitivity and selectivity were investigated. Limits of the detection of 7 dinitroanilines were in the range of 0.014–0.096 μg kg−1, and there were no interfering peaks (unlike in EI) in the complex matrices. Recoveries of 7 dinitroanilines in five matrices at three spiked levels (10, 20 and 40 μg kg−1) ranged from 61 to 126 % and the relative standard deviations were all below 12 %.