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Simultaneous Estimation of Glass–Water Distribution and PDMS–Water Partition Coefficients of Hydrophobic Organic Compounds Using Simple Batch Method

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posted on 15.09.2011 by Min-Kai Hsieh, Chung-Te Fu, Shian-chee Wu
A simple batch method by use of refilling and nonrefilling experimental procedures and headspace solid phase microextraction was applied to simultaneously obtain the glass–water distribution coefficients (KGW) and polydimethylsiloxane(PDMS)–water partition coefficients (KPW) of hydrophobic organic compounds (HOCs). The simple batch method takes into consideration the glass-surface bound HOCs and the corresponding equilibrium distribution of HOCs among the glass, water, headspace, and polydimethylsiloxane (PDMS). The KPW and KGW values of 53 PCB congeners were determined. The glass–bound fraction predominated over other fractions for highly chlorinated PCBs. Ignoring glass adsorption and assuming a complete mass balance could thus substantially underestimate the KPW for HOCs in traditional work. Good linear correlations of logα (the overall mass transfer rate constant) vs logKPW, logKPW vs logKOW, and logKGW vs logKOW were observed, with logα = −0.91 logKPW + 1.13, R2 = 0.93; logKPW = 1.032 logKOW – 0.493, R2 = 0.947; and logKGW = 0.93 logKOW – 2.30, R2 = 0.90. The KPW values from this study were compared with those in the literature. With an account of the glass adsorption, the accuracy of the KPW determination and the estimation of the dissolved concentration in water for highly hydrophobic compounds can be significantly improved.

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