Sensitive and Selective Potentiometric Sensor Based on Carbon Paste Electrode for Determining Cerium(III) Ions in Soil and Water Samples; Simplex Lattice Mixture Design Application

The present paper describes the fabrication of a new potentiometric sensor to determine Cerium(III) ion based on a carbon paste electrode (CPE) as an indicator electrode. Four components, including N,N-bis(salicylidene)-1,3-propanediamine as the ionophore, graphite powder, ionic liquid ([HMIM][PF6]) as the binder, and carboxyl functionalized MWCNTs as the modifier, was used to fabricate the CPE. The percentage of each CPE component was optimized using a simplex lattice mixture design, including 20 experimental runs. The optimum amount of ionophore, graphite powder, ionic liquid, and carboxyl functionalized MWCNTs was 0.1409, 0.5405, 0.2000, and 0.1186, respectively. The fabricated CPE with an optimum composite showed the Nernstian response in terms of 19.77 slope (mV/decade) and response time (<8 s) for the Ce(III) ion determination in the concentration range of 1.0×10-8-1.0×10-3 M with a proper detection limit (5.17×10-9 M). Besides, the potentiometric response of the sensor was constant in the pH range of 4-9. The sensor was successfully utilized to determine the endpoint of the Ce(III) ion titration with a standard solution of EDTA as a titrant. Also, the sensor was applied to analyze soil and real water samples with recoveries between 90.7-104.2% and RSDs lower than 3.94%. The advantages of the sensor include simple fabrication, low cost, easy operation, wide linear range, short response time, high lifetime, and suitable selectivity.