Dispersive liquid-liquid microextraction for the determination of herbicides of urea derivatives family in natural waters by HPLC

A method is proposed for determining 11 herbicides of the urea family at a level of 0.3–20 μg/L using HPLC with diode array detection at 240 nm. Herbicides are extracted from water samples by liquid-liquid microextraction with dichloromethane using ultrasonic dispersion. The recovery of pesticides is 53–98%; the coefficients of preconcentration 78–160. An analysis takes about 1 h; the relative standard deviation of results does not exceed 6%.