Determination of Eight Sulfonylurea Herbicide Residues by LC/MS/MS Using a Sample Separation Technique with Ethyl Acetate.

Background: Sulfonylureas are an important group of systemic herbicides mainly used for the control of weeds in cereals and other crops in early growth stages of their cultivations. Sulfonylureas are characterized by their broad spectrum weed control and their good crop selectivity. Objective: In the present study, the determination of eight sulfonylureas has been tested in wheat flour by applying the SweEt multiresidue method modified for dry products. Method: The method involves sample preparation with extraction with ethyl acetate (EEA) and determination of the analytes with LC/MS/MS-electrospray ionization. Its performance was compared with the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. Both methods were validated in three fortification levels according to European Union requirements. Results: The proposed method gave acceptable results as far as validation criteria are concerned, while QuEChERS did not result in successful recoveries in the lowest validation level, which is equal to the respective maximum residue limits (MRLs). Conclusions: The obtained results showed that the tested method showed good separation, sensitivity, linearity, precision, and accuracy for quantitative and qualitative analysis of sulfonylurea herbicides in cereals at low levels, as required by legislation. The analytical techniques were successfully applied to different samples of cereals, and no residues were determined above the reporting limit, as established at the lowest concentration level of each analyte being validated with acceptable accuracy. Highlights: Low recoveries for QuEChERS in the concentrations equal to the MRL. Acceptable recoveries for the EEA method in all fortification levels. Correlation coefficients above 0.99. Positive findings only with EEA in real samples.