Modified Lanthanum–Zeolite for Sensitive Electrochemical Detection of Heavy Metal Ions

Lanthanum-zeolite carbon paste electrode was synthesized and investigated as an alternative electrode for electrochemical detection of Pb(II) and Cd(II) ions. Prior to the analysis, mordenite zeolite with SiO ₂/ Al ₂O ₃ ratio of 15 was synthesized and characterized by XRD, SEM, EDX and XPS. Composite electrode was fabricated by mixing carbon graphite, lanthanum-impregnated zeolite and paraffin oil until a uniform paste was formed. Preliminary studies showed that the electrode with 2 wt% lanthanum impregnation (2 wt% La-MOR/CPE) gave a better response toward the detection of Pb(II) ion. Accumulation of Pb(II) ion was achieved at a potential of − 1.2 V (vs. Ag/AgCl) for 120 s followed by anodic stripping scan in the range of − 1.6 to 0 V. Analytical figures of merit for the 2 wt% La-MOR/CPE are comparable with other reported electrodes. The detection limit (S/ N= 3) for single detection of Pb(II) was 0.23 ppb. On the other hand for simultaneous detection of Pb(II) and Cd(II) ions, detection limits were found to be 0.24 and 0.12 ppb, respectively. The composite electrode demonstrates the potential to be used in the quantification of heavy metals due to its simplicity, low cost of fabrication, lack of toxicity, and speed of analysis.