Novel Composite Electrode Based on Graphite and Polyurethane without Isocyanates for Electroanalysis with Modulated pH Sensitivity

A composite was developed to align with the principles of green chemistry and the sustainable development goals, with a focus on its renewability, production, and degradation. Thus, a polymeric matrix-agglutinant, poly-(hydroxyurethane), was synthesized from carbonated macaw palm oil (derived from epoxidized oil and CO₂) and 1,6-hexanediamine. When combined with graphite, this material resulted in a solid composite exhibiting uniform graphite dispersion and moderate hydrophobicity, contributing to its applicability as an electrode material. The composite electrode demonstrated sensitivity to pH variations, enabling its application as a probe for both anionic (K₃[Fe-(CN)₆]) and cationic ([Ru-(NH₃)₆]-Cl₃) species. Its analytical performance was evaluated in the determination of sildenafil citrate (SIL) in phosphate buffer solutions at various pH values and in synthetic urine. The electrode exhibited a sensitive response for SIL detection, with a limit of detection (LOD) of 1.17 × 10^-7 mol L^-1, limit of quantification (LOQ) of 3.90 × 10^-7 mol L^-1, sensitivity of 0.1873 μA μmol L^-1, and a recovery of 100 ± 1% in synthetic urine.