A plant esterase-catalyzed electrochemical sensing strategy for organophosphorus pesticide using 2,6-dichlorophenolindophenol as signal probe and FeSAC-NPC as electrocatalyst

Organophosphorus pesticides (OPs) can inhibit cholinesterase activity, posing great risks to human health. This work presents a new plant esterase-catalyzed pesticide detection strategy based on the indirect modulation of the electrochemical signal of 2,6-dichlorophenolindophenol by OPs. In this strategy, 2,6-dichlorophenolindophenol was employed as signal probe to generate a quantifiable cathodic peak. 1-naphthol, a product of 1-naphthyl acetate hydrolysis catalyzed by white kidney bean esterase (WKBE), can reduce 2,6-dichlorophenolindophenol, leading to a decrease in the electrochemical signal. However, in the presence of OPs, the activity of WKBE was inhibited, which suppressed the production of 1-naphthol, so that the electrochemical signal of 2,6-dichlorophenolindophenol could be restored to some extent. Notably, the degree of signal recovery was positively correlated with the amount of pesticide. Moreover, an iron single-atom catalyst dispersed in N-doped porous carbon (FeSAC-NPC) was prepared and utilized as an electrocatalyst to modify the electrode. Due to the atomically dispersed iron sites, along with the porous structure and high specific surface area of the carbon support, FeSACNPC exhibited superior catalytic performance to enhance the sensing signal. Under optimal conditions, the sensor showed good performance in detecting trichlorfon, with a wide linear range of 5 ng/L to 1 x 105 ng/L and a low detection limit of 1.04 ng/L. The recoveries in actual samples varied from 92.96 % to 107.20 %, indicating the method's practicality. This research presents a new "2,6-dichlorophenolindophenol-WKBE" assay system for simple and cost-effective detection of trace OPs residues in food, also offers a single-atom catalyst capable of promoting electrochemical sensor performance.