Nitrite-sensitive liquid membrane electrodes based on metalloporphyrin derivatives

Abstract
Liquid membrane electrodes based on some metalloporphyrin derivatives exhibit an anti-Hofmeister selectivity pattern: NO2 > SCN > I > F > Br > Cl > ClO4 > NO3 . These derivatives include chloro(5,10,15,20-tetraphenylporphyrinato)indium, chloro[5,10,15,20-tetra(p-methoxyphenyl)porphyrinato]indium and chloro(2-nitro-5,10,15,20-tetraphenylporphyrinato)indium. The selectivity pattern is interpreted on the basis of the coordination chemistry of metalloporphyrins. The membrane electrode with optimum composition shows a linear potentiometric response towards nitrite ion in the range 6.3 × 10–5–0.1 mol l–1 with a slope of 51 mV/pNO2 and a detection limit of 5.0 × 10–6 mol l–1. The electrode was applied to the determination of nitrite in Chinese cabbage.

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