Determination of five polar herbicides in water samples by ionic liquid dispersive liquid-phase microextraction

A simple, rapid and efficient ionic liquid based on dispersive liquid-phase microextraction (IL-DLPME) method was developed for the determination of three triazine and two phenylurea herbicides in water samples. IL (1-hexyl-3-methylimidazolium hexafluorophosphate [C6MIM][PF6]) that dispersed completely into the water solution under controlled temperature was used as the extraction solvent. The analytes were easily concentrated into the ionic liquid phase. This technique combined the process of extraction and concentration of the analytes into one step and avoided use of the more common, toxic organic solvents. The factors affecting the extraction efficiency such as the IL volume, sample pH, extraction time, centrifugal time, dissoluble temperature and ionic strength were optimized. The extracts were analyzed by high-performance liquid chromatography (HPLC) coupled with diode array detector (DAD). Under the optimized conditions, recoveries (50.5-109.1%) were obtained for the target analytes in water samples. The calibration curves were linear and the correlation coefficient ranged from 0.9947 to 0.9973 in the concentration levels of 5-100 mu g L-1. The relative standard deviations (RSDs, n = 5) were 6.80-10.78%. The limit of detections (LODs) for the five polar herbicides were between 0.46 mu g L-1 and 0.89 mu g L-1.