Constant Potential Coulometric Measurements with Ca(2+)-Selective Electrode: Analysis Using Calibration Plot vs. Analysis Using the Charge Curve Fitting

The possibility of analysis using charge curve fitting in constant potential coulometric mode instead of using a calibration plot is explored, for the first time. The results are compared with the analysis based on the use of a calibration plot. A Ca(2+) ion-selective electrode, with and without an electronic capacitor in series, is used as a model system in pure solutions of CaCl(2). Both techniques delivered good results (error within 2%) when the final and the initial concentration values differed by not more than three times. Larger differences result in 10–25% error. The presence of an electronic capacitor in the measurement circuit and in series with the electrode, allows for significantly faster response.