PENTACOORDINATE ORGANOTIN COMPLEXES AS NEUTRAL CARRIERS FOR SALICYLATE-SELECTIVE PVC MEMBRANE ELECTRODES

Selectivity properties are established for three new electrodes prepar ed by incorporating three pentacoordinate organotin(IV) complexes, mon o(2,4-pentanedionato-o,o') tri(phenylmethyl)tin (DMTBS), mono(benzoyla cetonalo-o,o') tri(phenylmethyl)tin (MPTBS) and mono(dibenzoylmelhanat o-o,o') tri(phenylmethyl)tin (DPTBS) into plasticized PVC membranes. T hese electrodes exhibit linear response to salicylate and an anti-Hofm eister selectivity pattern with high specificity for salicylate over m any common anions. The results show that the potentiometric response c haracteristics are related to the structure of organic ligands. The de tection limit and the slope of the electrodes based on these pentacoor dinate organotin complexes exhibit a tendency to decrease as the subst ituent in organic ligands changes from a methyl group to a phenyl grou p. Electrodes prepared with DMTBS have the best detection limit and th e highest degree of selectivity and sensitivity for salicylate. The re sponse mechanism is also investigated by use of a.c. impedance and i.r . spectroscopic techniques. (C) 1998 Elsevier Science B.V. All rights reserved.