De Coensel Nathalie, Desmet Koen, Górecki Tadeusz, Sandra Pat
Laboratory of Separation Science, Department of Organic Chemistry, Ghent University, Krijgslaan 281 S4, B-9000 Gent, Belgium.
J Chromatogr A. 2007 May 25;1150(1-2):183-9. doi: 10.1016/j.chroma.2006.10.062. Epub 2006 Nov 13.
Polydimethylsiloxane-air partition coefficients (K(PDMS-A)) were determined using direct headspace analysis and headspace sorptive extraction (HSSE) with polydimethylsiloxane-coated (PDMS) stir bars. The partition coefficients were investigated for three compounds, p-dichlorobenzene (PDCB), naphthalene and camphor, all of which sublimate at room temperature and find use as moth repellents. In order to determine the K(PDMS-A) values of these compounds, the air concentration and the concentration present on PDMS, both at equilibrium, were measured. The results indicate that PDMS-air partition coefficients are proportional to octanol-air partition coefficients. Thus, the latter could be used to estimate the extraction efficiency of PDMS for these compounds in air. Alternatively, octanol-air partition coefficients for organic compounds could be estimated from the PDMS-air partition coefficient values. As expected, the PDMS-air (or octanol-air) partition coefficient increased with decreasing temperature. Importantly, the partition coefficients determined at saturated vapor pressures were lower than the values determined at lower analyte concentrations, with the differences being greater for compounds with larger partition coefficients. Consequently, caution should be exercised when applying K(PDMS-A) values determined at high analyte concentrations to measurements at lower concentrations, especially when the partition coefficients are large.
使用直接顶空分析法以及带有聚二甲基硅氧烷涂层（PDMS）搅拌棒的顶空吸附萃取（HSSE）法测定了聚二甲基硅氧烷 - 空气分配系数（K(PDMS - A)）。对三种化合物进行了分配系数研究，这三种化合物分别是对二氯苯（PDCB）、萘和樟脑，它们在室温下都会升华，常用作驱虫剂。为了确定这些化合物的K(PDMS - A)值，对处于平衡状态下的空气浓度和PDMS上的浓度进行了测量。结果表明，聚二甲基硅氧烷 - 空气分配系数与正辛醇 - 空气分配系数成正比。因此，后者可用于估算聚二甲基硅氧烷对空气中这些化合物的萃取效率。或者，有机化合物的正辛醇 - 空气分配系数可根据聚二甲基硅氧烷 - 空气分配系数值来估算。正如预期的那样，聚二甲基硅氧烷 - 空气（或正辛醇 - 空气）分配系数随温度降低而增大。重要的是，在饱和蒸气压下测定的分配系数低于在较低分析物浓度下测定的值，对于分配系数较大的化合物，差异更大。因此，在将高分析物浓度下测定的K(PDMS - A)值应用于低浓度测量时应谨慎，尤其是当分配系数较大时。
