Poly(vinyl chloride) matrix membrane electrodes for manual and flow injection determination of metal azides

Abstract

Novel poly(vinyl chloride) matrix membrane electrodes for the azide ion are developed, electrochemically evaluated and used for manual and flow injection determinations of soluble and insoluble metal azides. These electrodes incorporate iron(II) and nickel(II) bathophenanthroline–azide ion-pair complexes as ion exchangers and 2-nitrophenyl phenyl ether as a plasticizing solvent mediator. The electrodes exhibit (i) near-Nernstian response for 1 × 10^–1–3.5 × 10^–5 mol dm^–3 N₃– with an anionic slope of 56–57 mV decade^–1 of concentration; (ii) a wide working range of pH (6–12); (iii) a fast response time (<40 s); (iv) long-term stability (>1 month); and (v) reasonable selectivity for N₃– over many common anions. Interference caused by ClO₄–, ClO₃– and NO₃– can be easily tolerated by appropriate ion-exchange separation. Determination of as little as 0.8 µg cm^–3 of soluble azides shows an average recovery of 99.4% and a mean standard deviation of 0.4%. Insoluble metal azides can be similarly determined after prior solubilization with alkaline ethylenediamine-tetraacetic acid solution. Methods for measuring the solubility products of some sparingly soluble metal azides and for monitoring the concentration level of azide in primer mixtures are described. Significant advantages in terms of simplicity, sensitivity, selectivity and accuracy are offered by these electrodes.