In-syringe reversed dispersive liquid–liquid microextraction coupled to high performance liquid chromatography for the determination of sulfonylurea herbicide residues in cereal samples
A rapid and sensitive method has been developed for the determination of sulfonylurea herbicides in cereal samples by in-syringe reversed dispersive liquid–liquid microextraction (IS-R-DLLME) coupled to high performance liquid chromatography with diode array detection. Seven sulfonylurea herbicides were studied: thifensulfuron-methyl, metsulfuron-methyl, chlorsulfuron, rimsulfuron, bensulfuron-methyl, tribenuron-methyl, and primisulfuron-methyl. These compounds were successfully separated using reversed phase HPLC within 35 min. Parameters affecting the extraction efficiency, such as the type and volume of the extraction solvent and disperser solvent, extraction time, and the pH of the sample were investigated and optimized. IS-R-DLLME was performed using a 10 mL syringe. A low density solvent, 1-octanol, was used as the extraction solvent. Ethyl acetate was used as the disperser solvent. Under the optimum conditions, high enrichment factors in the range of 110 and 271 were obtained. Good linearities were obtained in the range of 0.1 μg L−1 to 500 μg L−1, with correlation coefficients higher than 0.9990 and the limits of detection ranging from 0.1 μg L−1 to 0.3 μg L−1. The present method was successfully applied for the determination of sulfonylurea herbicide in cereal samples, with recoveries of 80–103%.