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 Ca2+ ion-selective electrode, with and without an electronic capacitor in series, is used as a model system in pure solutions of CaCl2. 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.
Keywords: analysis; calcium ion activity; calibration plot; charge curve fitting; constant potential coulometry.