Getting rid of reference electrode in potentiometric multisensor measurements

Abstract

Reference electrodes are indispensable part of electroanalytical methods; however, their use may often limit the options for miniaturization of the measurement set-up which is an important requirement for handling small sample volumes in biomedical studies. This is also true for potentiometric multisensor systems (“electronic tongues”) that are currently being rapidly developed for numerous analytical applications. We describe an approach to potentiometric multisensor measurements allowing the elimination of reference electrode from the measurement scheme. The idea is based on the employment of “cross-voltages” – the potentials of the sensors measured against each particular sensor of multisensor array with subsequent chemometric processing of these data. In this scenario each sensor in turn becomes a pseudo-reference electrode, thus the overall measuring protocol is as simple as direct potentiometry with only difference at the data treatment stage, where chemometric processing is required to extract the analytical information. The feasibility of this scheme is demonstrated for analysis of several model mixtures and for real urine samples. The accuracy attained by this procedure is at least the same as in classical multisensor measurements scheme and in several cases the cross-voltage approach yielded two times better accuracy, thus proving the perspective of the proposed measuring protocol.