Lab Terra&Acqua Tech-Water Quality, Technopole of Ferrara and Department of Chemistry and Pharmaceutical Sciences, University of Ferrara, Ferrara, Italy.
Anal Chem. 2012 Aug 21;84(16):7138-45. doi: 10.1021/ac301442m. Epub 2012 Aug 2.
The adsorption behavior of four perfluoroalkyl acids, including the environmentally relevant perfluorooctanoic acid, has been investigated on a straight-chain perfluorohexyl adsorbent. The aim of this study was to probe the potential of perfluorinated materials for the analysis and enrichment of perfluoroalkyl analytes. Water/acetonitrile mixtures, to which formic acid had been added (generally, 0.1%), were employed as mobile phases. For all perfluorinated acids, a U-shaped retention profile was observed by changing the amount of acetonitrile in the mobile phase. This behavior has been correlated to the excess adsorption of the organic component on the adsorbent surface. The concept of perfluoromethylene selectivity has been defined as the ability of a chromatographic system to discriminate between molecules that differ by a single perfluoromethylene group. The contribution to the Gibbs free energy of phase transfer for the passage of a perfluoroalkyl carbon from the mobile to the stationary phase has been evaluated. This information, in addition to the traditional van't Hoff analysis, has also been used to estimate the analogous contribution for the transfer of a carboxylic unit. Finally, insights into the retention mechanisms of perfluoroalkyl acids on straight-chain perfluorohexyl sorbents are discussed.
本研究旨在探究全氟材料在分析和富集全氟烷基分析物方面的潜力，研究了四种全氟烷基酸（包括环境相关的全氟辛酸）在直链全氟己基吸附剂上的吸附行为。采用添加甲酸（通常为 0.1%）的水/乙腈混合溶液作为流动相。通过改变流动相中的乙腈含量，所有全氟酸均呈现出 U 形保留曲线。这种行为与有机组分在吸附剂表面的过量吸附有关。将全氟亚甲基选择性的概念定义为色谱系统区分仅相差一个全氟亚甲基基团的分子的能力。评估了全氟烷基碳从流动相转移到固定相的相间传递对吉布斯自由能的贡献。除了传统的范特霍夫分析外，还利用这一信息来估计羧酸单元转移的类似贡献。最后，讨论了全氟烷基酸在直链全氟己基吸附剂上的保留机制。
