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

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