In this work, an electrochemical sensor based on a highly efficient competitive method is proposed that uses SiO₂-PNPG as an adsorbent for the efficient detection of Pb(II) in soil. The silica (SiO₂) and N-phenylglycine (NPG) polymer (SiO₂-PNPG), synthesized using a one-pot polymer method, was applied to construct specific metal electrochemical sensors with high sensitivity. The high sensitivity and good selectivity were accomplished in the determination of Pb(II) due to the selective penetration and accumulative effect of SiO₂-PNPG. The correlation between the current response and the Pb(II) concentration presents a linear range from 2.12 to 15.78 μg mL⁻¹ with a detection limit of 0.166 μg mL⁻¹ (S/N = 3, R² = 0.9987). The sensitivity, reproducibility and stability of this sensor are promoted due to the facilitated electron transfer.