Determination of metoalchlor,acetochlor and butachlor residues in water samples using vortex-assisted liquid-liquid microextraction and gas chromatography analysis

A vortex-assisted liquid-liquid microextraction (VALLME) has been developed and used for extraction amide herbicides from water samples,followed by gas chromatography micro-cell electron capture detection (GC-μECD).Experimental factors affecting the extraction efficiency were investigated.For the optimized VALLME method,aliquots of 50 μL toluene used as extraction solvent was directly injected into 20 mL water in a 25 mL volumetric flask.The extraction solvent dispersed into the water phase under vigorously shaking with the vortex.After standing for several minutes,it could be cleared into two phases and easily collected in the volumetric flask for the following GC analysis.Enrichment factors (EF) larger than 500-fold and estimated limits of detection based on the S/N at 3 in a range of 3.0 to 4.5 ng/L were obtained.Lower practical Levels(LPL) were 0.05 μg/L for tap water,0.5 μg/L for snow water.The calculated calibration curves gave linearity with correlation coefficients (R2) greater than 0.997 at the concentration levels ranging from 0.02 to 5.0 μg/L.The proposed method has been successfully validated during the fortification experiments in tap water and snow water with acceptable recoveries ranging from 74.2% to 96.3%,with RSD of 4.9% to 12.1% obtained.