A colorimetric analytical method based on a TCPP–CuCo2O4-like peroxidase for the detection of trichlorfon

In this work, a highly sensitive colorimetric sensing platform was designed for the detection of trichlorfon based on inhibiting thiocholine (TCh)-induced redox reaction. 5,10,15,20-Tetracarboxyphenylporphyrin (TCPP) functionalized CuCo₂O₄ (TCPP-CuCo₂O₄) was synthesized to construct a colorimetric sensing platform for trichlorfon. In the presence of H₂O₂, TCPP-CuCo₂O₄ can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue ox-TMB, accompanied by a strong absorption peak at 652 nm, while acetylcholinesterase (AChE) can specifically hydrolyze acetylthiocholine (ATCh) into TCh, which can reduce ox-TMB back into colorless TMB, resulting in a lower absorbance at 652 nm. Trichlorfon can irreversibly inhibit the activity of AChE and thus recover the absorption peak. Under the optimized conditions, detection of trichlorfon has a wide linear range of 40-4000 ng mL^-1 with a linear correlation coefficient of 0.9904. The proposed method can be applied to the detection of trichlorfon in vegetables and has good application prospects.