Surface functionalization of natural hydroxyapatite by polymerization of β-cyclodextrin: application as electrode material for the electrochemical detection of Pb(II)

Abstract

A composite material prepared by polymerization of β-cyclodextrin (β-CD) on the surface of natural hydroxyapatite using citric acid as cross linker, was employed as electrode material for the detection of Pb(II). Hydroxyapatite was obtained from bovine bones, following a three-step procedure including pre-calcination, chemical treatment with (NH₄)₂HPO_4, and calcination. The structure and morphology of the pristine hydroxyapatite (NHAP_P0.5) and its functionalized counterpart (NHAP_p0.5-CA-β-CD) were examined using XRD, FTIR, and SEM. Upon deposition as thin film on a glassy carbon electrode (GCE), the ion exchange ability of NHAP_p0.5-CA-β-CD was exploited to elaborate a sensitive sensor for the detection of lead. The electroanalytical procedure was based on the chemical accumulation of Pb(II) ions under open-circuit conditions, followed by the detection of the preconcentrated species using differential pulse anodic stripping voltammetry. The reproducibility of the proposed method, based on a series of 8 measurements in a solution containing 2 μM Pb(II) gave a coefficient of variation of 1.27%. Significant parameters that can affect the stripping response of Pb(II) were optimized, leading to a linear calibration curve for lead in the concentration range of 2 × 10^-8 mol L^-1 - 20 × 10^-8 mol L^-1 (R² = 0.998). The detection limit (3S/m) and the sensitivity of the proposed sensor were 5.06 × 10^-10 mol L^-1 and 100.80 μA.μM^-1, respectively. The interfering effect of several ions expected to affect the determination of lead was evaluated, and the proposed sensor was successfully applied in the determination of Pb(II) ions in spring water, well water, river water and tap water samples.

Keywords: Electroanalysis; Hydroxyapatite; Lead; β-cyclodextrin.