Abstract: A method for the determination of four acetanilide herbicides including acetochlor, butachlor, propanil, and metolachlor in adzuki beans was established using ammonium sulfate-ethanol-based aqueous two-phase extraction combined with high performance liquid chromatography. In the aqueous two-phase extraction, the polarity of the alcohol-rich upper phase was more similar to that of the herbicides in the same organic solvent. The salt solution of the lower phase could effectively precipitate protein and fat. Based on the recoveries of the herbicides, the optimal pretreatment conditions were determined as follows: aqueous two-phase system containing 25% ethanol and 28% ammonium sulfate, and ultrasonic extraction for 1 min at 35 ℃. Avoiding the use of toxic organic solvents, the current method was environmentally friendly. The detection limits for acetochlor, butachlor, propanil, and metolachlor were 3.5, 7.1, 4.6 and 5.8 μg/kg, respectively. The average recoveries at spiked concentrations of 10 and 100 μg/kg ranged from 86.1% to 95.9%, with relative standard deviation equal to or lower than 4.5%.

Key words: aqueous two-phase extraction; acetanilide herbicides; high performance liquid chromatography; adzuki bean