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This research has successfully fabricated ion selective electrode (ISE) for Pb²⁺ using castor oil (<i>Ricinus communis</i> L.)-based polyurethane (PU) membrane with 1,10-phenanthroline as the active agent. The sensitivity of the Pb²⁺ ISE obtained is 27.25 mV/decade with a linear range of [Pb(NO₃)₂] of 10⁻¹⁰–10⁻⁵ M and a coefficient of determination (R²) of 0.959. The system response reaches stability after 25 s of measurement. The Pb²⁺ has a detection limit of 10⁻¹⁰ M and gives a stable response at pH 7–8 with a 15-day lifetime. The investigation of the selectivity of the ISE was performed using the mixed solution method with log Kij values of <1. The selectivity order of Pb²⁺ ISE against the foreign ions is Ag²⁺ > Ca²⁺ > K⁺ > Mg²⁺ > Cu²⁺ > Fe³⁺ > Cr³⁺> Zn²⁺ > Cd²⁺. The Pb²⁺ ISE shows acceptable reproducibility and repeatability with standard deviation values of 0.065 and 0.0079, respectively. Fourier transform infrared (FT-IR) spectra confirmed that 1,10-phenanthroline was responsible for the formation of the Pb²⁺ ion entrapment via complexation. Other characterizations (crystallinity, micro-surface morphology, and mechanical strength) suggest the degradation of the membrane structure integrity after the application. The analysis results of Pb levels using the Pb²⁺ ISE in artificial and wastewater samples were not significantly different from the atomic absorption spectroscopy (AAS) measurement.