Determination of Acid Herbicides in Plant Leaves Using a Modified QuEChERS Method and UHPLC-MS/MS

The use of herbicides to control weeds in crops, especially in soybeans, corn, and sugarcane, is a common practice, but it poses a risk to nearby sensitive crops, since herbicide drift is common and has caused phytotoxicity, resulting in reduced crop yield. Thus, the determination of acid herbicides in plant leaves is important but challenging due to the complexity of the matrix and compound characteristics. Considering this, an analytical method was developed and validated for the determination of 22 acid herbicides in plant leaves, using a modified QuEChERS procedure and ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) with a run time of 10 min. The optimized method involved the extraction of the hydrated sample with acetonitrile containing formic acid, partitioning with salts, and cleanup with graphitized carbon black. Validation presented recoveries from 71 to 118%, with RSD ≤ 19% and method limit of quantification of 5 µg kg−1 for most of the herbicides indicating satisfactory performance. The proposed method was applied to 50 plant leaf samples, 36 of which contained residues of at least one of the evaluated herbicides. The developed method is rapid and efficient and can be applied in routine analyses of acid herbicides in plant leaves.