Application of miniaturised ultrasonic extraction to the analysis of organochlorine pesticides in soil

A miniaturised ultrasonic extraction procedure was developed for the determination of different organochlorine pesticides (OCPs) in soil by gas chromatography (GC/μ-ECD). For an acetone–petroleum ether (1/1, v/v) as the extractor and a 5-min sonication, parameters such as sample amount, solvent volume and number of extraction steps were optimized by using a 23 factorial experimental design. Limits of detection ranged from 0.02 to 1.34 μg kg−1. The developed procedure was applied to three different real soil samples with different fortification levels (25, 50 and 100 μg kg−1) and recoveries were estimated in the 82–106% range with relative standard deviations lower than 15%. Performance of the procedure was compared with those involving traditional shaking flask, Soxhlet extraction and large-scale ultrasonic extraction. The proposed procedure requires small volumes of solvent and sample. It is viable, rapid and easy to use for analysis of OCPs in soils.