Taguchi OA25 Orthogonal Array Design for the Optimization of La3+-Selective Electrode Prepared by Sol-gel Technique

A sol-gel electrode, based on ethyl 1,2,3,4-tetrahydro-6-methyl-4-phenyl-2- thioxopyrimidine-5-carboxylate (ETMPTC) as a neutral ionophore, was successfully developed for the detection of La3+ in aqueous solutions. The electrode responds to La3+ ion with a sensitivity of 19.7±0.1 mV/ decade over the range 1.0×10?8–1.0×10?1 M and in a pH range of 3.0–10.0. The sol-gel electrode shows detection limit of 3.5×10?9 M. The influence of membrane composition, the pH of the test solution, and the interfering ions on the electrode performance was investigated. The proposed electrode shows good discrimination of La3+ ion from several cations. The effect of temperature on the electrode response showed that the temperature higher than 65°C deteriorates the electrode performance. The electrode was found to work well under laboratory conditions. This sensor not only was used as an indicator electrode in potentiometric titration of lanthanum ion against EDTA but also was used to determination of La3+ concentration in the presence of certain interfering ions.