Electrochemical Sensor with 4-Mercaptopyridine Modification for Trace Mercury Detection

Mercury ion (Hg
²⁺
) is highly toxic and can cause serious harm to human health. In this work, we report an easily fabricated and sensitive electrochemical sensor based on 4-mercaptopyridine (4-MPY) modified gold electrode for trace Hg
²⁺
detection without using complex biochemical reagents. Through the analyses of binding energy values and stability constants of various metal ion-pyridine complexes, it is found that Hg
²⁺
-pyridine complex shows relatively high binding energy and stability constant, which confirms the strong specific binding ability between Hg
²⁺
and 4-MPY and verifies the feasibility of the experimental scheme. Based on the principle of specific coordination between Hg
²⁺
and nitrogen of pyridine, trace Hg
²⁺
can be detected by either differential pulse voltammetry (DPV) or electrochemical impedance spectroscopy (EIS) methods. By EIS, the sensor shows a good logarithmic relationship in a wide range of 0.01 μg/L to 500 μg/L with a low limit of detection (LOD) of 0.002 μg/L.