Lanthanum (III) Ion Determination by a New Design Optical Sensor

A new selective and sensitive Lanthanum (La) ions optical sensor based on immobilization of N-(2-aminoethyl)-salicylaldimine (AESI) on a triacetylcellulose membrane was prepared. The prepared optode exhibited a linear range of 30-150 part per billion (ppb) of the La (III) ion concentration with a detection limit of 14.38 ppb. The response time of the newly designed optode was derived within 30-60 s, depending on the La (III) ion concentration, however is independent to the pH of the solution in the range of 3-5. The proposed optode indicated a low detection limit, fast response time, and also remarkable selectivity regarding to the number of transition metals ions (i.e. Ce³⁺, Cu²⁺, Cd²⁺, Cr³⁺, Zn²⁺, Hg²⁺, and Fe²⁺). The optode was successfully regenerated with a thiourea solution, and its response which might be reversible and reproducible showed the relative standard deviation of less than 1.48%. This optode was applied for determining the La (III) ions in water samples.