A Two-Component Mass Balance Model for Calibration of Solid-Phase Microextraction Fibers for Pyrethroids in Seawater
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- 作者：Wenjian Lao ; Keith A. Maruya ; David Tsukada
- 刊名：Analytical Chemistry
- 出版年：2012
- 出版时间：November 6, 2012
- 年：2012
- 卷：84
- 期：21
- 页码：9362-9369
- 全文大小：372K
- 年卷期：v.84,no.21(November 6, 2012)
- ISSN：1520-6882
文摘
Determination of the analyte-specific distribution coefficient between the aqueous and sorbing phases is required for estimation of the aqueous-phase concentration of the analyte of interest using polymeric materials. Poly(dimethylsiloxane)-coated solid-phase microextration (PDMS-SPME) fiber-water partition coefficient (Kf) values for eight common-use pyrethroids were determined using a two-compartment mass balance model and parameters determined in experimental seawater microcosms. Mass balance, epimerization, and aqueous-phase degradation (i.e., hydrolysis) were characterized using gas chromatography-negative chemical ionization mass spectrometry to facilitate Kf estimation. Of the eight pyrethroids, only bifenthrin exhibited increasing sorption on the SPME fiber over the entire time-series exposure, indicating that its Kf value could be estimated through a stable-compound model. The remaining pyrethroids were found to be unstable (half-life of <22 days), underscoring the importance of accounting for degradation in estimating Kf. The two-compartment model explained the experimental time-series data for bifenthrin (R2 > 0.98) and the remaining unstable pyrethroids (R2 > 0.7), leading to estimated values of log Kf between 5.7 and 6.4, after correcting for residual dissolved organic carbon (DOC) in the experimental seawater. These Kf values can be used to determine freely dissolved pyrethroid concentrations in the pg/L range using PDMS-SPME in fresh or seawater matrices under equilibrium conditions in laboratory or field applications.