Kramer Nynke I, van Eijkeren Jan C H, Hermens Joop L M
Institute for Risk Assessment Sciences (IRAS), Utrecht University, P.O. Box 80177, NL-3508 TD Utrecht, The Netherlands.
Anal Chem. 2007 Sep 15;79(18):6941-8. doi: 10.1021/ac070574n. Epub 2007 Aug 21.
Because of its simplicity, solid-phase microextraction (SPME) is an increasingly popular technique to use in experiments measuring freely dissolved concentrations of compounds in biological and environmental samples. However, a number of studies have shown that sorption kinetics of compounds in such SPME systems is dependent on the presence of a binding matrix. This affects the interpretability of nonequilibrium SPME data. In this study, this phenomenon was investigated by measuring the rate of depletion of pyrene from a "loaded" poly(dimethylsiloxane) fiber into surrounding cell culture medium containing different concentrations of bovine serum albumin (BSA). The rate of depletion was found to steadily increase with increasing concentrations of BSA. It was postulated that BSA facilitated the transport of pyrene through the medium. This phenomenon was modeled by considering diffusion of BSA-bound pyrene in addition to diffusion of unbound pyrene in the aqueous boundary layer (BL) around the fiber. The model closely fit the experimental data and illustrated that diffusion in the BL was rate limiting because the analyte's affinity for the fiber was high and the BL thickness significant. The concentration of binding matrix and the analyte's affinity for the matrix further determined the extent to which BSA-facilitated transport contributed to the kinetics of the system.
由于其操作简便，固相微萃取（SPME）在测量生物和环境样品中化合物自由溶解浓度的实验中越来越受欢迎。然而，多项研究表明，此类SPME系统中化合物的吸附动力学取决于结合基质的存在。这影响了非平衡SPME数据的可解释性。在本研究中，通过测量芘从“负载”的聚二甲基硅氧烷纤维中消耗到含有不同浓度牛血清白蛋白（BSA）的周围细胞培养基中的速率，对这一现象进行了研究。发现消耗速率随着BSA浓度的增加而稳步增加。据推测，BSA促进了芘在培养基中的传输。通过考虑除了未结合的芘在纤维周围水相边界层（BL）中的扩散之外，结合了BSA的芘的扩散，对这一现象进行了建模。该模型与实验数据紧密拟合，并表明边界层中的扩散是速率限制因素，因为分析物对纤维的亲和力很高且边界层厚度可观。结合基质的浓度以及分析物对基质的亲和力进一步决定了BSA促进传输对系统动力学的贡献程度。
