Liquid membrane electrodes based on aza compounds for the determination of organic anions

N.V. Shvedene, N.N. Belchenko, N.V. Starushko, V.E. Baulin, I.V. Pletnev

Vestnik MGU (Proc. Moscow Univ.), Ser.2, in press (1997)

ABSTRACT. Electrochemical properties of PVC-plasticized membranes based on amines, in particular, tripodal with terminal phosphinoxy groups, were studied in solutions of oxo-, mono- and dicarboxylic acids, as well as of anionic surfactants. The membrane containing 5% of ionophore tris-[2-(2-diphenylphosphinyl)phenoxyethyl]amine and plasticized with o-nitrophenyl octyl ether shows a near-Nerstian response to dodecyl sulfate (slope= 56 mV/dec, Cmin= 2.5*10(-5) M) and to salicylate-anion (55 mV/dec and 6.3*10(-5) M, respectively). The electrodes demonstrate fast response (5-10 sec) in a broad range of pH (2-9). Membrane is capable to distinguish between cis- and trans-isomers of dicarbonic acids, maleic and fumaric, in monoanion form. Also, the distinction between positional isomers - phthalic and terephthalic acids - is achieved, potentiometric selectivity coefficient pht-/tpht- being 5.9*10(-2). Developed ISEs were used for the determination of anionic surfactants in cosmetics and salicylic acid in wine.

Laboratory of Preconcentration