Combined use of electroanalytical methods to derive calibration plots for species difficult to standardize

A simple method is described for the derivation of calibration graphs for electroactive active analytes which are difficult to standardize from a calibration for an easily standardized reference species dissolved in the same medium. The method is based on evaluation of the ratios between the current-signals recorded for the analyte and for the reference solution by rotating-disk-electrode voltammetry and by an electroanalytical technique based on stationary electrodes which provides purely diffusion-controlled responses (e.g., chronoamperometry or normal-pulse voltammetry). This approach can be applied to all electroactive species which undergo diffusion-controlled processes, regardless of the degree of reversibility involved. Reliability tests, done with electroactive organic species dissolved in dimethyl sulphoxide, show that both accuracy and precision are within ±5%. The method is applied to the determination of hydrogen and oxygen solubilities in dimethyl sulphoxide and acetonitrile, respectively, as an example of quantitative evaluations of species which are difficult to standardize.