POLAROGRAPHIC STUDIES AND MEASUREMENTS OF NITRITE IN COBALT(II) THIOCYANATE ASCORBIC-ACID SOLUTION

In the cobalt(II)-thiocyanate-ascorbic acid solution (pH = 2.0), nitrite can form a ternary complex (CoSCNNO)+, which can be reduced at mercury electrode to -0.59 V (vs. SCE). The wave can be used for the polarographic determination of traces of nitrite in the concentration range of 1 x 10(-8)-8 x 10(-7) M (single sweep polarography), 1 x 10(-7)-4 x 10(-5) M (differential pulse polarography), or 1.5 x 10(-6)-2 x 10(-4) M (direct current polarography). The mechanism of the electrode process is studied by linear sweep voltammetry, DC polarography, cyclic voltammetry, double-step chronocoulometry, and controlled potential coulometry. The polarographic wave is ascribed to the reduction of nitrogen monoxide in the complex to hydroxyamine. The procedure is used for the direct determination of nitrite in various real samples.