Predicting the end point potential break values: A case of potentiometric titration of lipophilic anions with cetylpyridinium chloride

Abstract

The applicability of cetylpyridinium chloride for potentiometric titration of lipophilic anions has been studied. The specially developed cetylpyridinium-selective plasticized electrode has been used for the investigation of the mechanism of interaction between the cetylpyridinium cation and lipophilic anions, which obviously goes through the association reaction resulting in the formation of water-insoluble precipitates. The investigated 54 anions were placed in the selectivity row that strongly correlates with lipophilicity. Additionally, an attempt has been made to find a simple and reliable descriptor suitable for prediction of the value of the end point potential break and thus indicating the applicability of the described potentiometric method for determination of untested lipophilic anions of interest. It has been established that despite being well known lipophilicity estimators, molar weight, octanol–water distribution coefficient logP, logarithm of solubility logS, and hydrophilicity-lipophilicity index can not be separately used for directly predicting the end point potential break values. However, simultaneous analysis of the above descriptors by using the multiple linear regression technique has resulted in the development of a reasonable QSPR model for the estimation of the potential break values near the end point.