Ion-selective electrode with fixed quaternary phosphonium ion-sensing species

Abstract

The response properties and selectivity of polymer membrane electrodes with fixed quaternary phosphonium ion-sensing groups for nitrate are described. A poly(trioctylvinylbenzylphosphonium nitrate)(PTOVBPNO₃) membrane electrode demonstrated a selective response to nitrate in the concentration range 5 × 10^–5–0.1 mol dm^–3, with a slope of –53.4 ± 0.5 mV decade^–1. The selectivity of this electrode for nitrate ions can be favourably compared to conventional nitrate ion-selective electrodes based on quaternary ammonium ion-exchange sites. Notably, a significant improvement of selectivity for nitrate by two orders of magnitude was obtained in the presence of perchlorate. The PTOVBPNO₃ membrane electrode was used for the determination of nitrate in samples of commercially available fertilizers.