Ionic liquid-based aqueous two-phase system extraction of sulfonamides in milk

A simple method for the determination of six sulfonamides (SAs) in milk samples was developed. 1-Butyl-3-methylimidazolium tetrafluoroborate and trisodium citrate dihydrate were used to form aqueous two-phase system. The aqueous two phase system was applied to the extraction of the SAs and the determination of the analytes was performed by high-performance liquid chromatography. To achieve optimum extraction performance, several experimental parameters, including the type and the amount of salt, the type and amount of ionic liquid, ultrasonic time and pH of sample solution, were investigated and optimized. Under the optimal experimental conditions, good linearity was observed in the range of 8.55–1036.36 ng mL−1. The limits of detection and quantification were in the range of 2.04–2.84 and 6.73–9.37 ng mL−1, respectively. The present method was successfully applied to the determination of SAs in milk samples, and the recoveries of analytes were in the range of 72.32–108.96% with relative standard deviations ranging from 0.56 to 12.20%. The results showed that the present method was rapid, feasible and environmentally friendly.