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