Determination of Trace Organophosphorus Pesticides in Water Samples by Solid Phase Disk Extraction and Gas Chromatography-Thermionic Specific Detector

Abstract

A simple, rapid, sensitive, and high-throughput method based on solid-phase disk extraction (SPDE) and a gas chromatography–thermionic specific detector (GC-TSD) is described for the determination of organophosphorus pesticides (OPPs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions found were 500 mL water sample (pH 2.5–7.0) extracted and enriched by a C18 (octadecyl) solid phase extraction disk at flow rate of 5 to 50 mL/min and eluted by 5 mL of acetone and 3 × 5 mL methylene chloride. The linearity of the method ranged from 0.020 to 1.00 µg/L for dimethoate, methyl parathion, and malathion, with correlation coefficients ranging between 0.9976 and 0.9992. The concentration factors for OPPs were between 498 and 554. The limits of detection were in the ng/L level, ranging between 2.5 and 4 ng/L. The relative recoveries of spiked 3 OPPs (dimethoate, methyl parathion, and malathion) with external calibration method at different concentration levels in pure, fresh water, and sea water samples were 102–112%, 94–109%, and 99–104%, respectively, and with relative standard deviations of 4.1–6.2%, 3.4–4.6%, and 3.5–5.2% (n = 3), respectively. It is concluded that this method can be successfully applied for the determination of OPPs in pure water, fresh water, and sea water samples.

Keywords:

• Gas chromatography-thermionic specific detector
• Organophosphorus pesticides
• Solid phase disk extraction
• Water samples

Acknowledgments

This work was supported by Zhejiang Province Test Analysis of Science and Technology Plan Projects (No. 2012C37022) and the Key SQT Innovation Team of Zhejiang Province for Agro Products Standards and Testing Technology No. 2010R20028 and Research project foundation for high level professionals of Qingdao Agricultural University (No. 631104).

Notes

^a DLR stands for the concentration of the analytes spiked in 500 mL of ultrapure water.

^b y and x stand for the peak area and the concentration (mg/L) of the analytes in 1 mL aceton after SPDE, respectively.

^c Data taken from the present work, and LOD stands for the concentration of the analytes spiked in 500 mL of ultrapure water.

The authors have declared no conflict of interest.