Determining Chemical Activity of (Semi)volatile Compounds by Headspace Solid-Phase Microextraction

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• 作者：Charlotte N. Legind ; Ulrich Karlson ; Joel G. Burken ; Fredrik Reichenberg ; Philipp Mayer
• 刊名：Analytical Chemistry
• 出版年：2007
• 出版时间：April 1, 2007
• 年：2007
• 卷：79
• 期：7
• 页码：Mayer
• 全文大小：112K
• 年卷期：v.79,no.7(April 1, 2007)
• ISSN：1520-6882

文摘

This research introduces a new analytical methodology formeasuring chemical activity of nonpolar (semi)volatileorganic compounds in different sample matrices usingautomated solid-phase microextraction (SPME). Thechemical activity of an analyte is known to determine itsequilibrium concentration in the SPME fiber coating. Onthis basis, SPME was utilized for the analytical determination of chemical activity, fugacity, and freely dissolvedconcentration using these steps: (1) a sample is broughtinto a vial, (2) the SPME fiber is introduced into theheadspace and equilibrated with the sample, (3) theSPME fiber is injected into the GC for thermal desorptionand analysis, and (4) the method is calibrated by SPMEabove partitioning standards in methanol. Model substances were BTEX, naphthalene, and alkanes, whichwere measured in a variety of sample types: liquidpolydimethylsiloxane (PDMS), wood, soil, and nonaqueous phase liquid (NAPL). Variable sample types (i.e.,matrices) had no influence on sampling kinetics becausediffusion through the headspace was rate limiting for theoverall sampling process. Sampling time was 30 min, andrelative standard deviations were generally below 5% forhomogeneous solutions and somewhat higher for soil andNAPL. This type of activity measurement is fast, reliable,almost solvent free, and applicable for mixed-mediasampling.