A novel environmentally friendly approach for ultra-trace determination of erbium in alloys and environmental samples

A novel, environmentally benign optical sensor membrane has been developed for the ultra-trace determination of erbium (Er³⁺) in alloys and environmental samples. The sensor incorporates norfloxacin (NFX) and cetylpyridinium chloride (CPC) into a chitosan-silica composite (2 : 1 volume ratio) prepared via an optimized sol-gel process. The resulting sensor demonstrated excellent selectivity at pH 9.3 and exhibited a response time of three minutes. A linear response was observed for concentrations spanning from 5 × 10^-6 to 7.5 × 10^-9 M, with a correlation coefficient (r ²) of 0.9975. The limit of detection (LOD) and limit of quantitation (LOQ) were determined to be 2.2 × 10^-9 M and 7.3 × 10^-9 M, respectively. Precision and accuracy assessments showed a relative standard deviation (% RSD) of 1.46 and a recovery percentage (% recovery) of 100.96%. Along with its high stability and reproducibility, the sensor exhibited remarkable selectivity for Er³⁺ ions over common cations. The optode was successfully applied to Er³⁺ analysis in alloys, binary mixtures, and water samples.