Highly selective and sensitive detection of cadmium ions by horseradish peroxidase enzyme inhibition using a colorimetric microplate reader and smartphone paper-based analytical device

With the knowledge of the extent of damage caused by cadmium ions (Cd2+), it becomes imperative to detect the presence of Cd2+ in drinking water with a rapid, efficient, and selective analytical method. Herein, a facile and novel colorimetric method for detecting cadmium ions, based on the irreversible inhibition of horseradish peroxidase (HRP) enzyme was established. Alternatively, a low-cost and affordable paper-based analytical device integrated with a smartphone platform was further designed to visualize, on-site and quantitative detection of Cd2+. The method developed for Cd2+ detection is of great interest to ensure a rapid diagnosis of water quality. Under the optimal conditions, the limit of detection of cadmium ions was 0.1 ppb, which is much lower than the permissible limit of WHO (5 ppb) for human exposure. Interference measurements showed that the method exhibited good selectivity. The proposed method was successfully applied as a rapid screening for cadmium ions monitoring in drinking water.