PVC MEMBRANE ELECTRODES FOR MANUAL AND FLOW-INJECTION DETERMINATION OF TETRAPHENYLBORATE - APPLICATIONS TO SEPARATE AND SEQUENTIAL TITRATIONS OF SOME METAL-IONS

Three novel poly (vinyl chloride) matrix membrane electrodes, highly s ensitive and selective for tetraphenylborate anion (TPB), are develope d and electrochemically evaluated. They are based on the use of iron(I I) bathophenanthroline, nickel(II) bathophenanthroline-and nitron-TPB ion-pair complexes as electroactive materials with dioctylphthalate (D OP) and 2-nitrophenyl phenyl ether (NPPE) as plasticizing solvent medi ators. The electrodes exhibit stable and rapid near-Nernstian response for 10(-2)-10(-6) M TPB over the pH range 4-10. Use of these electrod es for direct potentiometric determination and potentiometric titratio n of as low as 1 mug of TPB/ml and 0.6 mg of TPB/ml give results with average recoveries of 99.3% (mean standard deviation 0.5%) and 99.4% ( mean standard deviation 0.2%), respectively. Incorporation of nitron-T PB PVC sensor in a flow-through sandwich cell provides an efficient fl ow-injection detector for determining TPB with an input rate of at lea st 60 samples/hr. The limit of detection is 1.6 mug TPB/nil in a 20-mu l sample. The electrodes am also used to monitor separate and sequenti al titrations of some metal ions with TPB. Alkaline earth and transiti on-metal ions upon reaction with polyethylene glycol and ethylenediami ne, respectively, form cationic complexes readily titrated with TPB. O ptimum conditions are outlined for sequential titrations of various co mbinations of metallic species.