A Colorimetric Strategy for Arsenic(V) Determination in Rice via Boosting the Peroxidase-like Activity of NCuzyme

Arsenic (As) is extremely poisonous, and prolonged exposure greatly raises the likelihood of developing cancer. It is crucial to develop selective and sensitive methods for detecting As. In this study, using melamine and Cu(II), a Cu-based complex (NCuzyme) with peroxidase (POD)-like activity was prepared using a green and simple approach for the first time. NCuzyme can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with H₂O₂ to form a blue product (oxTMB). The addition of As(V) can boost the POD-like activity of NCuzyme, deepening the blue color and increasing the absorbance signal of the reaction system. Therefore, a colorimetric method has been developed for the detection of As(V). This method exhibits excellent selectivity for As(V), with a linear range of 4-150 μg/L and a limit of detection of 3.35 μg/L, which is below the limit for arsenic in drinking water (10 μg/L) set by the World Health Organization. Finally, the developed colorimetric sensing method has been successfully applied to detect As(V) in real sample (rice), with good recovery rates (93.3-102.9%) and an RSD of less than 2.3%. In summary, the colorimetric method developed based on enhancing POD-like activity of NCuzyme provides a rapid and simple method for the As(V) detection.