In this study, a polyethylene Pasteur pipette-based ultrasound-assisted emulsification microextraction (USAEME) applying low-density organic solvent was successfully developed for the extraction of trace levels of organochlorine pesticides (OCPs) in water samples and followed by gas chromatography-mass spectrometry (GC-MS) analysis. In this approach, a polyethylene Pasteur squeeze-type pipette was employed as a convenient extraction device and ultrasound radiation was applied to accelerate the emulsification of low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OCPs in water samples. Thirty microliters of extraction solvent (isooctane), of lower density than water, were injected into the aqueous sample solution held in the pipette. The latter was then immersed in an ultrasound water bath to form an emulsion. After 30s extraction, phase separation was achieved by centrifugation. The upper layer (isooctane) was collected and analyzed by GC-MS. No disperser solvent was required in this procedure. Significantly, fast analysis and high extraction efficiency were achieved. Another feature of the procedure was the use of the pipette as the extraction device, which permitted less dense than water organic solvent to be used as extraction solvent. This method broadens the applicability of USAEME to a wider range of solvent. Additionally, carry-over problems were avoided with the use of the disposable pipette. Parameters affecting the efficiency of polyethylene Pasteur pipette-based USAEME, such as the extraction solvent, extraction solvent volume, extraction and centrifugation time, ionic strength and extraction temperature were investigated. Under the optimum conditions, the proposed method provided good enrichment factors (EFs) in the range of 128 and 328, with relative standard deviations (RSDs) ranging from 2.7% to 12.4%. The limits of detection were in the range of 0.8 and 10ng/L depending on the analytes. The linearities were between 0.01 and 50μg/L for hexachlorobenzene, dieldrin, endrin and o,p'-DDD, 0.05-25μg/L for heptachlor, and 0.005-50μg/L for p,p'-DDE. Finally, the polyethylene Pasteur pipette-based USAEME was successfully used for the fast determination of OCPs in river and tap water samples. The proposed method provides a simple, convenient, rapid, sensitive, cost-effective, and environmentally friendly process for the determination of OCPs in water samples.
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