Zirconia coated stir bar sorptive extraction combined with large volume sample stacking capillary electrophoresis-indirect ultraviolet detection for the determination of chemical warfare agent degradation products in water samples

摘要

In this study, a sensitive, selective and reliable analytical method by combining zirconia (ZrO _2) coated stir bar sorptive extraction (SBSE) with large volume sample stacking capillary electrophoresis-indirect ultraviolet (LVSS-CE/indirect UV) was developed for the direct analysis of chemical warfare agent degradation products of alkyl alkylphosphonic acids (AAPAs) (including ethyl methylphosphonic acid (EMPA) and pinacolyl methylphosphonate (PMPA)) and methylphosphonic acid (MPA) in environmental waters. ZrO _2 coated stir bar was prepared by adhering nanometer-sized ZrO _2 particles onto the surface of stir bar with commercial PDMS sol as adhesion agent. Due to the high affinity of ZrO _2 to the electronegative phosphonate group, ZrO _2 coated stir bars could selectively extract the strongly polar AAPAs and MPA. After systematically optimizing the extraction conditions of ZrO _2-SBSE, the analytical performance of ZrO _2-SBSE-CE/indirect UV and ZrO _2-SBSE-LVSS-CE/indirect UV was assessed. The limits of detection (LODs, at a signal-to-noise ratio of 3) obtained by ZrO _2-SBSE-CE/indirect UV were 13.4-15.9μg/L for PMPA, EMPA and MPA. The relative standard deviations (RSDs, n=7, c=200μg/L) of the corrected peak area for the target analytes were in the range of 6.4-8.8%. Enhancement factors (EFs) in terms of LODs were found to be from 112- to 145-fold. By combining ZrO _2 coating SBSE with LVSS as a dual preconcentration strategy, the EFs were magnified up to 1583-fold, and the LODs of ZrO _2-SBSE-LVSS-CE/indirect UV were 1.4, 1.2 and 3.1μg/L for PMPA, EMPA, and MPA, respectively. The RSDs (n=7, c=20μg/L) were found to be in the range of 9.0-11.8%. The developed ZrO _2-SBSE-LVSS-CE/indirect UV method has been successfully applied to the analysis of PMPA, EMPA, and MPA in different environmental water samples, and the recoveries for the spiked water samples were found to be in the range of 93.8-105.3%.