Two dispersive liquid–liquid microextraction methods coupled with gas chromatography–mass spectrometry for the determination of organophosphorus pesticides in field water
Shang-Ping Chu A , Chun-Kai Huang B , Pai-Shan Chen C D E and Shang-Da Huang A E
+ Author Affiliations
- Author Affiliations
A Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
B Department of Chemistry, National Chung-Hsing University, Taichung 40227, Taiwan.
C Department and Graduate Institute of Forensic Medicine, National Taiwan University, Taipei 10002, Taiwan.
D Forensic and Clinical Toxicology Center, National Taiwan University, College of Medicine and National Taiwan University Hospital, Taiwan.
E Corresponding authors. Email: sdhuang@mx.nthu.edu.tw; paishanchen@ntu.edu.tw
Environmental Chemistry 11(6) 661-672 https://doi.org/10.1071/EN14091
Submitted: 30 April 2014 Accepted: 30 June 2014 Published: 5 November 2014
Environmental context. Conventional sample pretreatment for the determination of pesticides in environmental samples is time consuming and labour intensive. We report two dispersive liquid–liquid micro-extraction methods that provide rapid homogeneous emulsification in aqueous samples within 2 min. These simple and environmentally friendly extraction methods are particularly suitable for the measurement of organophosphorus pesticides in field water.
Abstract. The methods up-and-down shaker-assisted dispersive liquid–liquid microextraction (UDSA-DLLME) and water with low concentration of surfactant in dispersed solvent-assisted emulsion dispersive liquid–liquid microextraction (WLSEME) were developed for the analysis of 13 organophosphorus pesticides (OPPs) in water samples by gas chromatography–mass spectrometry (GC-MS). UDSA-DLLME required only 14 μL of 5-methyl-1-hexanol as the extraction solvent. The use of an up-and-down shaker allowed homogeneous and rapid emulsification of aqueous samples. OPP extraction was completed in 2 min. In WLSEME, a mixture containing 9 μL of the extraction solvent (1-heptanol) and 250 μL of water as the dispersed solvent (containing 10 mg L–1, Triton X-100) was withdrawn and expelled four times within 10 s using a microsyringe to form a cloudy emulsion in the syringe. This emulsion was then injected into 5 mL of aqueous sample spiked with all of the above OPPs. The total extraction time was ~0.5 min. After optimisation, the linear range of the method was 0.1–100 μg L–1 for UDSA-DLLME and 0.05–100 μg L–1 for WLSEME. The coefficient of determination was greater than 0.9958. The limits of detection ranged from 0.040 to 0.069 μg L–1 for UDSA-DLLME and 0.020 to 0.035 μg L–1 for WLSEME. Analyses of river water, lake water and underground water had absolute recoveries of 34 to 96 % and relative recoveries of 84 to 115 % for both methods. Other emulsification methods such as vortex-assisted, ultrasound-assisted and manual-shaking-enhanced ultrasound-assisted methods were also compared against the proposed UDSA-DLLME and WLSEME methods. The results reveal that UDSA-DLLME and WLSEME provided higher extraction efficiency and precision.
Additional keywords: field water, OPPs, organophosphorus pesticides, UDSA-DLLME, up-and-down shaker-assisted dispersive liquid–liquid microextraction, water with low concentration of surfactant dispersive liquid–liquid microextraction, WLSEME
References
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