Studies on lead ion-selective electrodes based on polyalkoxylates

Abstract

The performance of the tetraphenylborate (TPB) salts of lead complexes with non-ionic surfactant polyalkoxylates, namely polyethylene glycol 1540 (PEG 1540), Antarox CO-880 and polypropylene glycol 425 (PPG 425) as the active sensors for Pb²⁺ ions in poly(vinyl chloride)(PVC) membrane electrode systems has been assessed using 2-nitrophenyl phenyl ether (NPPE), dioctylphenyl phosphonate (DOPP) or dipentylpentyl phosphonate (DPPP) and their mixtures as plasticising solvent mediators. The PVC electrode based on Pb. Antarox CO-880. TPB-NPPE showed a higher selectivity towards Pb²⁺ ions in the presence of a large number of interferent metal ions and had a near Nernstian response between 10^–1 and 10^–5 mol dm^–3 of Pb²⁺.

In terms of range, the next best electrode was that based on Pb. PPG-425. TPB-DOPP, but this suffered from more interferences than the Pb. PPG-425. TPB-NPPE analogue and was of short range (down to 10^–4 mol dm^–3). The three electrodes, Pb. Antarox CO-880. TPB-NPPE, Pb. PPG-425. TPB-DOPP and Pb.PPG-425. TPB-20% DOPP + 80% NPPE, showed good end-point breaks in the potentiometric titration of sulphate in 80% ethanolic solutions with lead perchlorate, the best being the electrode based on Pb. PPG-425. TPB-DOPP. However, the lead(II) titrant system is susceptible to the interference by hydrogen peroxide that can occur in some analytes.