Optimization and application of SPME for the gas chromatographic determination of endosulfan and its major metabolites in the ng L~(-1) range in aqueous solutions

摘要

In the present study an analytical method was optimized for the determination of α-endosulfan, β-endosulfan, endosulfan sulfate, endosulfan ether and endosulfan lactone in small volumes of environmental aqueous samples using solid-phase microextraction (SPME) and gas chromatography-electron capture detection (GC-ECD). A 100 μm polydimethylsiloxane (PDMS) phase was used for the extraction. The limit of detection (LOD) for the analytes varied between 0.01 and 0.03 μg L~(-1) with a relative standard deviation of 3 to 11. The influence of the ionic strength on the extraction efficiency was investigated for the individual compounds. α-Endosulfanβ-endosulfan, endosulfan sulfate and endosulfan ether were extracted successfully without salt addition. The extraction efficiency of endosulfan lactone was improved with 30 NaCl content. A general decrease in extraction efficiency for α-endosulfan, β-endosulfan, endosulfan sulfate and endosulfan ether with high NaCl content (20-30) in the solution was observed due to glass surface adsorption. No effect of dissolved organic material (DOM) on the extraction efficiency was observed. The extraction coefficients changed between Log K=2.17 and 3.33. A sample from the Antarctic region was analyzed using the optimized GC-ECD/SPME method. To confirm the results obtained for the real sample a GC with a mass spectrometer (MS) was used. Endosulfan sulfate, the most toxic metabolite of endosulfan, was found in the sample at a concentration of 0.3 μg L~(-1).