A sensitive colorimetric sensor for detection of sodium dehydroacetate based on Cu,Fe-PMs with peroxidase-like...

A phosphomolybdate nanozymes doped with copper and iron particles (Cu,Fe-PMs) with excellent peroxidase (POD)-like activity was prepared by one-step microwave digestion method. It can oxidize the positively charged substrates such as 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂, resulting in the formation of a blue compound. It is noteworthy that the POD-like activity of Cu,Fe-PMs was significantly boosted upon the incorporation of sodium dehydroacetate (DHA). This was attributed to the formation of complex between the Cu,Fe-PMs and DHA. On the one hand, DHA enhances the affinity of Cu,Fe-PMs for the substrate and exhibits superior catalytic properties. On the other hand, DHA also accelerated the valence state transformations between Fe³⁺/Fe²⁺ and Cu⁺/Cu²⁺, increased catalytic active sites and facilitate the generation of more reactive oxygen species (ROS) such as •OH with strong oxidation. Therefore, the current study successfully established a highly sensitive and reliable colorimetric sensor for detecting the DHA content in foods. The results indicated that the absorbance at 652 nm exhibited a linear relationship with DHA concentration within the range of 0.0017-2.5 μg mL^-1, achieving a minimum limit of detection (LOD) as low as 0.83 ng mL^-1. The sensor was successfully applied to detect DHA in actual samples, with recoveries ranging from 91.59% to 103.35% and a relative standard deviation (RSD) not exceeding 3.64%. This demonstrates the reliable performance and consistent reproducibility of the analytical approach.