Synthesis and electrochemical applications of tetraaqua-bis (2,4-dichlorophenoxyacetato) chromium(III) chloride monohydrate modified glassy carbon electrode for simultaneous detection of Cd, Hg, and Mn in environmental samples

Abstract

This study focused on the synthesis and comprehensive characterization of a new complex [Cr(DCPA) 2 (H 2 O) 4 ]Cl.H 2 O, and its application as a high-performance modifier in an electrochemical sensor for the simultaneous detection of Cd, Hg, and Mn ions. Spectroscopic techniques (Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-Vis) and thermal (TGA) analyses confirmed the coordination geometry and thermal stability of the complex, while electrochemical characterization (CV, EIS) demonstrated a significant increase in electroactive surface area and enhanced electron-transfer kinetics upon electrode modification. The developed sensor was used to simultaneously detect Cd, Hg, and Mn ions by differential pulse anodic stripping voltammetry (DPASV). The buildup of metal ions on the electrode surface was carried out in 0.1 M acetate buffer solution (ABS, pH 6.0) by applying a potential of -1.2 V versus Ag/AgCl for 120 s. After a 15-second rest period, the DPASV was stripped during the positive-potential scan. For simultaneous detection, the sensor showed a linear range of 0.2 to 10 mg/L for all three metals, with regression equations of Ipa (μA) = 48.16C + 27.82 (R 2 = 0.9914), Ipa (μA) = 31.89C + 8.55 (R 2 = 0.9923), and Ipa (μA) = 7.26C + 15.8 (R 2 = 0.9941), yielding LODs of 0.0511, 0.0615, and 0.0556 mg/L and LOQs of 0.1686, 0.2029, and 0.1852 mg/L, for Cd, Hg and Mn, respectively, under ideal experimental conditions. In addition, the precision of the simultaneous analysis was confirmed by repeatability (n = 7 trials) RSDs of 0.41%, 0.82%, and 0.13% and reproducibility (n = 4 electrodes) RSDs of 3.14%, 4.72%, and 0.086% for Cd, Hg, and Mn with RSD < 5.0%, thereby advancing the theoretical and practical research applicability of the sensor for the detection of heavy metals. Long-term stability for seven days showed retention rates of 90.22% (Cd), 88.98% (Hg), and 87.25% (Mn). Finally, the sensor was successfully applied to water, juice, and milk samples, achieving satisfactory recoveries of 80.04-98.67% (Cd), 80.00-107.15% (Hg), and 80.02-114.58% (Mn).