A Simple and Label-Free Detection of As(3+) using 3-nitro-L-tyrosine as an As(3+)-chelating Ligand

A simple and rapid As(3+) detection method using 3-nitro-L-tyrosine (N-Tyr) is reported. We discovered the specific property of N-Tyr, which specifically chelates As(3+). The reaction between As(3+) and N-Tyr induces a prompt color change to vivid yellow, concomitantly increasing the absorbance at 430 nm. The selectivity for As(3+) is confirmed by competitive binding experiments with various metal ions (Hg(2+), Pb(2+), Cd(2+), Cr(3+), Mg(2+), Ni(2+), Cu(2+), Fe(2+), Ca(2+), Zn(2+), and Mn(2+)). Also, the N-Tyr binding site, binding affinity, and As(3+)/N-Tyr reaction stoichiometry are investigated. The specific reaction is utilized to design a sensor that enables the quantitative detection of As(3+) in the 0.1–100 μM range with good linearity (R(2) = 0.995). Furthermore, the method’s applicability for the analysis of real samples, e.g., tap and river water, is successfully confirmed, with good recoveries (94.32–109.15%) using As(3+)-spiked real water samples. We believe that our discovering and its application for As(3+) analysis can be effectively utilized in environmental analyses such as those conducted in water management facilities, with simplicity, rapidity, and ease.