The influence of high ionic strength on the potentiometric determination of pH 4.0 (25 °c, I = 1.0 mol L-1) in acidified brine of preserved hearts of palm

Abstract

The aim of this study was to evaluate the influence of ionic strength (I) on the potentiometric pH measurement of solutions with high I such as the Acidified Brine of Preserved Hearts of Palm (ABPHP) as it is accurately measured only in dilute solutions where I £ 0.1 mol L-1 as defined by Debye-Hückel's theory. Standard calibrators were developed to evaluate a potassium biphthalate buffer solution (BS4: pH 4.0 at 25 °C) with the variation of I of the medium. In practical application, the objective is the optimization of the potentiometric pH measurements of solutions having high I, for example, ABPHP with an I of 0.98 mol L-1 (1). The choice of this procedure is justified because ABPHP has a naturally high I that is not consistent with Debye-Hückel's theory. This can make pH measurements unreliable. From a public health point of view, the botulism often implicated these preserved vegetables, and the potentiometric pH measurement is the only legal parameter for quality control employed to improve sanitary control actions. The quantitative variables (position and dispersion) were calculated as mean, maximum and minimum values, standard deviation and coefficient of variation. Moreover, the Grubbs’ test was used to identify possible outliers and their homogeneity, thereby demonstrating the linear tendency of the results. Student's t-test and ANOVA with a 95% confidence index were used to verify the variability of the results. The results are promising, since by altering the I of the medium (I > 0.1 mol L-1), there was a change in the pH of the solution. This study is important to ensure a true quality control in the production of preserved hearts of palm.