Rapid on-site detection of chromium contamination in foods using a naked-eye DMSA-AuNPs colorimetric sensor

The extensive use of chromium in various industrial processes may cause toxic effects in organisms due to its accumulation in the environment and foods. Traditional methods for chromium detection are time-consuming and infeasible for on-site usage. It is urgent to build a rapid, real-time and economical method for determining chromium to ensure human health and environmental safety. Here we developed an optimized colorimetric method for rapid detection of Cr 3+ ion based on the specific chromium chelator 2′3-dimercaptosuccinic acid (DMSA) which was screened by a novel biological method. Chemical methods further verified the specificity of DMSA for chromium. Both in vitro and in vivo experiments demonstrated that DMSA is safe for utilization. DMSA was complexed with gold nanoparticles (AuNPs) to increase the specificity and sensitivity for Cr 3+ . The optimized DMSA-AuNPs reaction achieved a color change from wine red to blue upon adding Cr 3+ at less than 5 μM. The naked-eye visual detection limit was 0.5 μM with a total reaction time of less than 1 min. The linear range of this colorimetric sensor was 0.5–5 μM and the detection limit reached 23 nM. The Cr 3+ detection by DMSA-AuNPs across several food samples including rice, soybean, milk, grape, peach and cabbage was consistent with those determined by inductively coupled plasma-mass spectrometry. Its detection results in 6 food samples (rice, soybean, milk, etc.) are highly consistent with ICP-MS (correlation coefficient R 2  > 0.99), and the entire detection process can be completed within 1 min. Our study provides an original and practical method for rapid, safe, on-site and cost-effective chromium monitoring of water, foods and the environment.