Nouvelle méthode de dosage automatique de substances oxydantes ou réductrices par potentiométrie différentielle : Partie I. Étude théorique

A new method is proposed for routine determinations of oxidizable and reducible substances. A mathematical development and criticism of the method of Schierjott has led to a fundamental modification of the earlier experimental conditions (ratio of the oxidized/reduced forms of the reagent at the start and end of the redox reaction). This improvement allows a considerable increase in the sensitivity of the method and is particularly advantageous for the determination of substances of low reactivity, e.g. carbohydrates. Other advantages are a reduction in the quantity and thus cost of the necessary reagent, and a decreased risk of precipitation of the substances involved. The mathematical treatment of the proposed version allows a rigorous theoretical comparison of the two methods. An evaluation of the quality of the approximations introduced into both methods is also proposed, based on the calculation of the deviation (absolute and relative differences) of approximated values from theoretical values. The final part of the work deals with optimization of the different principal parameters, i.e. concentration of the reagent, temperature and reaction time.