MODELING OF POTENTIOMETRIC ELECTRODE ARRAYS FOR MULTICOMPONENT ANALYSIS

The use of a four-electrode array comprising three highly selective and one sparingly selective electrode for the determination of sodium, potassium, and calcium ions in tertiary mixtures of the cations is described. The response surface of each electrode in the array is determined by using mixed calibration solutions and this response modeled via the Nickolskii-Eisenmann equation by using a variety of optimization procedures. The combination of highly and sparingly selective sensors offers considerable advantages over existing single-electrode measurements, such as polling of predictions, resulting in improved accuracy and precision, and diagnosis of electrode performance without recalibration. The ability of the array to determine sodium, potassium, and calcium ions at physiological levels in tertiary mixtures with less than 2.8% error is demonstrated. Unlike traditional single-electrode measurements, the modeled array can accurately determine low levels of individual cations in the presence of a large and widely varying excess of the other two. The application of the modeled array to the simultaneous determination of the three cations in human plasma samples is considered.