Nitric oxide solutions: standardisation by chronoamperometry using a platinum disc microelectrode

Studies on the anodic oxidation of nitric oxide (NO) at platinum microdiscs have been performed. Results obtained with platinum disc microelectrodes of various radius values showed that the process is mass transport controlled. At 0.9 V (versus Ag/AgCl), current-time data were analysed according to an analytical expression that describes the chronoamperometric transient at a disc microelectrode and allows the determination of the diffusion coefficient of the electroactive species as well as its concentration. From chronoamperometric curves obtained by using a 25 mu m radius platinum microelectrode, the concentration of NO in saturated solutions prepared at 25 degrees C in phosphate buffer (pH 7.4) was found to be (2.1 +/- 0.3) x 10(-3) mol dm(-3). In the same supporting electrolyte, the data led to the calculation of the diffusion coefficient of NO, the value being 1.2 x 10(-5) cm(2) s(-1).