Determination of trace amounts of nitrite by single-sweep polarography

A single-sweep polarographic determination of nitrite in 0.2 M sulphuric acid medium containing nickel(II) sulphate and ammonium thiocyanate is described. The ternary complex (NiSCNNO)⁺ which is formed in the solution is strongly adsorbed on the surface of the mercury electrode and an adsorptive polarographic wave at ?0.57 V (vs. SCE) is related to the concentration of nitrite in the range 2.0 × 10^?8-1.0 × 10^?6 M. The detection limit is 8 × 10^?9 M. The relative standard deviation is 1.5% and the regression coefficient is 0.998. Most common anions and cations do not interfere. The mechanism of the electrode process was studied by several electrochemical methods. The polarographic wave is attributed to the reduction of nitrogen monoxide in the adsorbed (NiSCNNO)⁺ complex to hydroxylamine. The procedure was applied to the determination of trace amounts of nitrite in sausage, water and nitrate.