Catalytic spectrophotometric determination of nitrite using the chlorpromazine–hydrogen peroxide redox reaction in acetic acid medium

Abstract

In a 0.2 mol l^–1 acetic acid–6.6 × 10^–3 mol l^–1 oxalic acid medium at 20 °C, 5 × 10^–3 mol l^–1 chlorpromazine hydrochloride (CPH) was oxidized by 5 × 10^–2 mol l^–1 H₂O₂ with the reaction being catalysed by nitrite ions. The maximum absorbance occurs within 2–4 minutes of the start of the oxidation reaction and is proportional to the nitrite concentration; this allows the determination of nitrite in the range 3–1500 ng ml^–1. Reagent concentrations, except for CPH, have little effect on the determination. The effects of experimental conditions and foreign ions are described. The interference of iron(III) can be masked by oxalic acid and ethylenediaminetetraacetic acid. The method was applied to the determination of nitrite in rain and river water.