ELECTROCHEMISTRY OF THE NITROPRUSSIDE ION - FROM MECHANISTIC STUDIES TO ELECTROCHEMICAL ANALYSIS

The electrochemical reduction of the nitroprusside ion (NP) was examin ed by differential-pulse polarography and square-wave voltammetry. The effect of pH on the electrochemical behaviour of NP was studied and e xperimental evidence for the occurrence of adsorption of the products of the first one-electron reduction of NP is shown, Owing to the adsor ption of these products,which are the reactants in the second reductio n step of NP, the peak current of the second process is highly enhance d compared with that of the first process, especially at low concentra tion levels (< 1 x 10(-5) mol dm(-3)). For acidic solutions the enhanc ement is considerably higher than at pH greater than or equal to 7. A surface reaction leading to the regeneration of the reactants of the s econd reduction process can be advanced as a possible explanation, Squ are-wave cathodic stripping voltammetry with adsorptive accumulation w as used for the determination of NP, The detection limit depends on th e square wave parameters and can be as low as 2.3 nmol dm(-3) for a de lay time of 60 s.