Górecki T, Martos P, Pawliszyn J
Department of Chemistry and Waterloo Centre for Groundwater Research, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.
Anal Chem. 1998 Jan 1;70(1):19-27. doi: 10.1021/ac9703515.
Various approaches to the analysis of polar compounds in different matrixes by solid-phase microextraction (SPME) were studied. The analysis of polar analytes in nonpolar matrixes was performed with custom-made SPME fibers coated with Nafion perfluorinated resin. The sensitivity of this fiber in this type of analysis was better by 1 order of magnitude on average as compared to those of any of the commercially available fibers. The fiber was the most sensitive for the most polar of the compounds studied, i.e., methanol. Determination of methanol, ethanol, and 2-propanol in unleaded gasoline was illustrated. Except for methanol, the fiber did not perform very well in the analysis of alcohols in water. The fiber was capable of extracting water from benzene. SPME analysis of polar compounds in water was studied using aqueous solutions of acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), 2-propanol, 2-methyl-2-propanol, and tetrahydrofuran. Fibers coated with poly(dimethylsiloxane)/divinylbenzene yielded the highest sensitivity in this type of analysis. Low- or sub-ppb detection limits were obtained for all the analytes with FID detection when the samples were saturated with NaCl. Since fibers of this type extract analytes by adsorption rather than absorption, nonlinear responses were observed when all the analytes were allowed to equilibrate because of the limited number of adsorption sites on the surface of the coating and displacement of compounds with low distribution ratios by compounds with high distribution ratios (mainly MIBK). Two approaches allowed a significant improvement in linearity: extraction of a vigorously stirred sample for a short time, or extraction under static conditions for a time much shorter than that required for equilibration of all the analytes. In both cases the amount of MIBK extracted was significantly reduced, while the remaining analytes were affected to a much lesser degree. The sensitivity of acetone determination was greatly improved by in-solution derivatization with o-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride and extraction of the oxime formed.
研究了通过固相微萃取（SPME）分析不同基质中极性化合物的各种方法。使用涂覆有全氟磺酸（Nafion）全氟树脂的定制SPME纤维对非极性基质中的极性分析物进行分析。与任何市售纤维相比，这种纤维在这类分析中的灵敏度平均高1个数量级。该纤维对所研究的极性最强的化合物即甲醇最为灵敏。文中举例说明了在无铅汽油中测定甲醇、乙醇和2-丙醇的情况。除甲醇外，该纤维在分析水中的醇类时表现不佳。该纤维能够从苯中萃取水。使用丙酮、甲乙酮、甲基异丁基酮（MIBK）、2-丙醇、2-甲基-2-丙醇和四氢呋喃的水溶液研究了水中极性化合物的SPME分析。涂覆有聚（二甲基硅氧烷）/二乙烯基苯的纤维在这类分析中灵敏度最高。当样品用氯化钠饱和时，采用火焰离子化检测器（FID）检测，所有分析物均获得了低至亚ppb级的检测限。由于这类纤维通过吸附而非吸收来萃取分析物，当所有分析物达到平衡时，由于涂层表面吸附位点数量有限以及高分配比的化合物（主要是MIBK）取代低分配比的化合物，因此观察到非线性响应。有两种方法可显著改善线性：剧烈搅拌样品短时间萃取，或在静态条件下萃取，萃取时间远短于所有分析物达到平衡所需的时间。在这两种情况下，MIBK的萃取量均显著降低，而其余分析物受到的影响程度要小得多。通过用盐酸邻-（2,3,4,5,6-五氟苄基）羟胺进行溶液内衍生化并萃取形成的肟，大大提高了丙酮测定的灵敏度。
