title: Potentiometric responses of polymeric liquid membranes based on hydrophobic chelating agents to metal ions.
abstract: The effect of hydrophobicity of acidic chelating agents as sensing materials on the potentiometric responses of polymeric liquid membranes was investigated. The chelating agents tested were 8-quinolinol (HOx), dithizone (HDz), 1-(2-pyridylazo)-2-naphthol (PAN) and their alkylated analogues, 5-octyloxymethyl-8-quinolinol (HO8Q), di(phexylphenyl)thiocarbazone (C6HDz), 7-pentadecyloxy-1-(2-pyridylazo)-2-naphthol (C15PAN) and a series of N-alkylcarbonyl-N-phenylhydroxylamines (CnPHA, n = 3, 6, 9, 12). The distribution coefficients between membrane solvent and water were determined to evaluate the hydrophobicity of the agents. The potential-pH profiles of the membranes containing hydrophobic chelating agents demonstrated the generation of potentiometric responses, while less hydrophobic agents gave no response. A possible model for the generation of membrane potential is proposed. The charge separation is attained by the permselective uptake of metal cations by the chelating agent anion at membrane/solution interface, where the high hydrophobicity of the agent enables the anionic or deprotonated form of the agents to remain at the membrane/solution interface.
authors.affiliation: Hokkaido Institute of Public Health, Sapporo 060-0819, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Itoh
authors.forename: Y
authors.initials: Y
authors.lastname: Ueda
authors.forename: A
authors.initials: A
authors.lastname: Hirano
authors.forename: M
authors.initials: M
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Tohda
authors.forename: H
authors.initials: H
authors.lastname: Akaiwa
authors.forename: Y
authors.initials: Y
authors.lastname: Umezawa