A robust calculation approach applied to the evaluation of hydrogen ion concentrations through potentiometric measurements in aqueous solutions.

The data analyzed in this work were generated following the methodology developed by Molina et al. (J. Electroanal. Chem., 1979) for the calibration of a potentiometric system of measurement of hydrogen-ion concentrations resulting from neutralizations, at 25 degreesC, of acidic or alkaline solutions at constant ionic strength (0.1 mol.l(-1)) held with NaClO4. The observed data present a serious deviation in relation to the mathematical model derived from the Nernst equation, for pH values ranging from 3 to 11, where pH=-log[H+]. We show that the minimization of the sum of the absolute values of the residuals gives estimates that are not influenced by outlying values.