Abstract
A novel carbon paste electrode utilizing a lisinopril molecule as a recognition element for the selective determination of free Ca2+ ions was developed. The fabrication of the sensor was established by the covalent attachment of lisinopril to the surface of the MWCNTs-NiO nanocomposite. The formed composite was characterized by FT-IR, TEM, and XRD. This unique design has led to high selectivity and stability of the studied carbon paste electrode. It revealed a Nernstian slope of 30.4 ± 0.52 mV/decade with wide linearity ranging from 1×10-2 mol L-1 to 1×10-8 mol L-1. The electrode showed high sensitivity to Ca2+ ion. The LOD was found to be 3.5×10-9 mol L-1. The proposed sensor was successfully applied for the determination of Ca2+ concentration in various media such as pharmaceutical tablets, tap water, soil drainage water samples and human serum samples. The resulted recovery of the sensor was in the range of 94.2% - 102.1% with acceptable precision and reproducibility.