Synthesis, characterization and electrochemical investigation of NaPb4−xCax(PO4)3 (0 ≤ x ≤ 1.5) in capturing cadmium (II)

Single deficient apatites phase type NaPb4−xCax(PO4)3 (CaLA) have been synthesized by solid state reaction. The ceramics were characterized by XRD, FTIR and Raman spectroscopy at room temperature. Then, its Rietveld refinement inferred hexagonal crystal structure with the space group P63/m. Consequently, a good agreement was obtained between the experimental and the simulated intensities evaluated in terms of R-factors. The prepared apatites were used as modifiers of carbon paste electrode (CPE). These sensors (CaLA-CPE) were used to determine cadmium (II) using differential pulse anodic stripping voltammetry (DPASV). The best signal was obtained using NaPb2.5Ca1.5(PO4)3 deficient apatite. This result was explained by the substitution of the lead by calcium especially in the active sites. Thereafter, the factors affecting the accumulation and electrode reaction steps were investigated and an optimized procedure was developed. A calibration plot for cadmium (II) concentration in the range 1.0 × 10−6-1.0 × 10−4 mol L−1 was obtained under the optimized conditions. The limit of detection was found to be 6.41 × 10−7 mol L−1. The developed methodology is demonstrated to be useful for quantifying cadmium (II) in seawater and mussel samples.