Optimization of Castor Oil-Based Ion Selective Electrode (ISE) with Active Agent 1,10-Phenanthroline for Aqueous Pb²⁺...

This research has successfully fabricated ion selective electrode (ISE) for Pb2+ using castor oil (Ricinus communis 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.