Determination of sulfonylurea herbicides in soil by ionic liquid-based ultrasonic-assisted extraction high-performance liquid chromatography

A high-performance liquid chromatography method for determination of sulfonylurea herbicides in soil has been developed. Prior to the determination, sample preparation was performed by ionic liquid-based ultrasonic-assisted extraction (IL-based UAE). Dried soil powder was mixed with a room temperature ionic liquid, [C6MIM][BF4], to form a suspension, and then ultrasonic extraction was performed in a water bath at ambient temperature. The chromatographic separation was performed using a C18 chromatographic column with gradient elution mode. The method was validated by evaluating the repeatability, linearity, precision, and applicability. The limits of detection ranged from 7.7 ng g−1 to 11.3 ng g−1 and the limits of quantification were between 25.6 ng g−1 and 37.6 ng g−1. The calibration curves showed a good linear relationship (r > 0.9990) in the concentration ranges of 50.0–25 000 ng g−1 for nicosulfuron and 50.0–5000 ng g−1 for metsulfuron-methyl, bensulfuron-methyl and pyrazosulfuron-ethyl. The recoveries ranged from 81.1 to 100.1% with relative standard deviations lower than 7.44%. The IL-based UAE is free of volatile organic solvent, and consumes less sample, time and solvent, compared with regular ultrasonic and Soxhlet extractions. There was no obvious difference in the extraction recoveries of sulfonylurea herbicides obtained by the three methods.