Evaluation of organochlorine pesticides in soil using ultrasound-assisted liquid phase microextraction

A simple and inexpensive sample pretreatment method, ultrasound-assisted liquid phase microextraction, combined with a novel solvent layering technique, was developed for extraction of organochlorine pesticides from soil. Samples were analyzed by gas chromatography with an electron capture detector. Of five possible extraction solvents tested, xylene, with a density of 0.86 g mL−1, was selected for further method development. Soil samples and solution were mixed in an ultrasonic water bath and separated using centrifugation. The extraction solvent was collected on the solution surface using a pipette. Parameters, such as extraction solvent type and volume, extraction time, and NaCl concentration were optimized. Under optimal conditions, recoveries ranged from 71.6% to 114.6% and correlation coefficients ranged from 0.9961 to 0.9996. Detection limits, calculated as 3× the signal-to-noise ratio, were from 0.04 to 0.18 μg L−1. The standard deviations ranged from 6.7% to 19.6%.