A sol-gel polydimethylsiloxane/polythiophene coated stir bar sorptive extraction combined with gas chromatography-flame photometric detection for the determination of organophosphorus pesticides in environmental water samples.

In this work, a new method of polydimethylsiloxane/polythiophene (PDMS/PTH) coated stir bar sorptive extraction (SBSE) coupled to liquid desorption-large volume injection-gas chromatography-flame photometric detection (LD-LVI-GC-FPD) was proposed for the determination of organophosphorus pesticides (OPPs, including phorate, fenitrothion, malathion, parathion and quinalphos) in environmental water samples. Polythiophene was synthesized by chemical oxidative polymerization method, and the PDMS/PTH coated stir bar was prepared by sol-gel technique. The preparation reproducibility of PDMS/PTH coated stir bar was good with the relative standard deviations (RSDs) ranging from 3.9% to 8.1% (n=7) in one batch, and from 5.9% to 14.9% (n=6) among different batches. To get the best extraction performance for OPPs, the operation parameters affecting the extraction efficiency of SBSE, including extraction time, desorption time, stirring rate and ionic strength, were investigated. Under the optimal conditions, the limits of detection (S/N=3) were found to be in the range of 0.011-0.038 μg/L for the five target OPPs, and the linear range was from 0.2 to 100 μg/L for phorate and 0.1-100 μg/L for other four OPPs. The RSDs of the proposed method were in the range of 4.0-9.8% (n=8, c=1 μg/L) and the enrichment factors were varied from 56.7 to 80.9-fold (theory enrichment factor was 100-fold). The proposed method was applied to the analysis of OPPs in East Lake water and ground water samples with recovery in the range of 77.7-119.8% and 79.1-109.8% for the spiked East Lake water and ground water samples, respectively.