Biocapture platform based on α-poly-l-lysine functionalized SWCNTs for lead monitoring

This work reports the development of an efficient electrochemical sensing strategy for Pb(II) quantification based on glassy carbon electrodes (GCE) modified with single-walled carbon nanotubes (SWCNTs) covalently functionalized with α-poly-l-lysine (α-PLys). The resulting platform enables the selective preconcentration of Pb(II) at open-circuit potential (OCP) through affinity-driven complexation with the primary amino groups of the α-poly(l-lysine) residues immobilized on the SWCNT surface, which is further reduced in a fresh supporting electrolyte solution at -1.20 V, potential that is applied solely to convert the surface-confined Pb(II) into metallic Pb prior to stripping detection. The analytical signal was obtained from the oxidation of Pb by differential pulse voltammetry (DPV) in 0.020 M acetate buffer (pH 5.00). A linear response was obtained over the concentration range from 2.5 to 400.0 μg L^-1, with a sensitivity of (0.065 ± 0.001) μA μg^-1 L and a detection limit of 0.75 μg L^-1. The sensor exhibited high selectivity in the presence of elevated concentrations of potentially interfering species. The applicability of the proposed platform was successfully demonstrated using Pb(II)-spiked surface water samples, showing excellent recoveries and strong agreement with inductively coupled plasma mass spectrometry (ICP-MS).