The simultaneous analysis of sulfonylurea herbicide residues in fruit samples using ultrasound-assisted surfactant-enhanced emulsification microextraction coupled with high-performance liquid chromatography
Ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) coupled with high-performance liquid chromatography-diode array detection (HPLC-DAD) has been developed for the preconcentration and determination of five sulfonylurea herbicides (SUHs) (thifensulfuron-methyl, metsulfuron-methyl, rimsulfuron, tribenuron-methyl and primisulfuron-methyl) in fruit samples. In this study, Tween 20 served as an emulsifier and chloroform was the extraction solvent. Several variables, such as type and volume of extraction solvents, type and concentration of surfactants, salt addition, ultrasound emulsification time and centrifugation time were investigated and optimized. Under the optimum conditions, high enrichment factors (EFs) were achieved ranging from 76 to 166. Limits of detection (LODs) ranged between 0.005 and 0.8 ng mL−1. Linearities were obtained in the range of 0.01 to 100 ng mL−1, with correlation coefficients greater than 0.998. Matrix matched calibration was used for the quantitative analysis of the target SUHs in fruit samples (apple, pineapple and watermelon). A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used for sample preparation before UASEME and analysis. No contamination by the targeted SUHs in samples was observed. High accuracy with recoveries of fortified samples at three levels (0.0075, 0.01 and 0.025 mg kg−1) ranging from 79 to 105% were obtained. Low LODs of the studied SUHs in fruit samples were in the range of 0.02–2 μg kg−1 which are below the maximum residue limits (MRLs) established by EU-MRLs.