A novel approach for the determination of the toal concentration of acids in aqueous solutions by simultaneous diffusion limited current for reduction of acids and pH measurements

摘要

A novel method is presented for the detection of acid content in aqueous solutions. The method is based on simultaneous measurements, in the test solution, of the overall steady-state limiting current arising from the reduction of the acids, and pH, along with the use of a theoretical expression. The current is recorded with platinum mieroelectrodes. while pH is measured ~Ii ~ ‘~las.s etectrodes To retate current and pH data, an “amperometric calibration” of the glass electrodes is performed.X~rat&o~x eog.susiows axe ohtained from, a senes of combined current/PH measurements in so1uxson~ containing a range or concentrations of the strong acid HClO4. This procedure overcomes the problems associated with the unknown activity coefficient of H± and liquid junction potential contributions involved in the pH measurements. The new methodology is tested in several aqueous solutions containing mono- and polyprotic acids either alone or in mixture; buffered solutions are also considered. It is shown that, under the latter conditions, special cases exist. in which the total acid concentration is achieved by overall steady-state limiting current measurements alone. The accuracy of the proposed method is tested against classical titration procedures. The discrepancies between the two methods do not exceed approx 5%.