Fluorophilic Ionophores for Potentiometric pH Determinations with Fluorous Membranes of Exceptional Selectivity
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- 作者：Paul G. Boswell ; Csongor Szí ; jjá ; rtó ; Markus Jurisch ; John A. Gladysz ; Jó ; zsef Rá ; bai ; Philippe Bü ; hlmann
- 刊名：Analytical Chemistry
- 出版年：2008
- 出版时间：March 15, 2008
- 年：2008
- 卷：80
- 期：6
- 页码：2084 - 2090
- 全文大小：114K
- 年卷期：v.80,no.6(March 15, 2008)
- ISSN：1520-6882
文摘
Ionophore-doped sensor membranes exhibit greater selectivities and wider measuring ranges when they areprepared with noncoordinating matrixes. Since fluorousphases are the least polar and least polarizable liquidphases known, a fluorous phase was used for this workas the membrane matrix for a series of ionophore-basedsensors to explore the ultimate limit of selectivity. Fluorous pH electrode membranes, each comprised of perfluoroperhydrophenanthrene, sodium tetrakis[3,5-bis(perfluorohexyl)phenyl]borate, and one of four fluorophilicH+-selective ionophores were prepared. All the ionophores are highly fluorinated trialkylamines containingthree electron withdrawing perfluoroalkyl groups shieldedfrom the central nitrogen by alkyl spacers of varyinglengths: [CF3(CF2)7(CH2)3]2[CF3(CF2)6CH2]N, [CF3(CF2)7(CH2)3]2(CF3CH2)N, [CF3(CF2)7(CH2)3]3N, and [CF3(CF2)7(CH2)5]3N. Their pKa values in the fluorous matrix are ashigh as 15.4 ± 0.3, and the corresponding electrodesexhibit logarithmic selectivity coefficients for H+ over K+as low as <-12.8. The pKa and selectivity follow thetrends expected from the degree of shielding and thelength of the perfluoroalkyl chains of the ionophores.These electrodes are the first fluorous ionophore-basedsensors described in the literature. The selectivities of thesensor containing [CF3(CF2)7(CH2)5]3N are not only greaterthan those of analogous sensors with nonfluorous membranes but were of the same magnitude as the bestionophore-based pH sensors ever reported.