A novel colorimetric probe with positive correlation between toxicity and the reaction for the assessment of chromium ions

Different valence states of chromium ions possess huge differences in toxicity. Hence, it is an innovative idea to design a reasonable probe to detect Cr according to the toxicity characteristics of different valence states. We report a novel, rapid, simple and accurate probe for the detection of Cr3+ and Cr6+ ions. As a probe, gold nanoparticles (Au NPs) are successfully modified using tartaric acid (TA) and 2-[4-(2-hydroxyethyl)-1-piperazinyl] ethanesulfonic acid (HEPES) via a two-step modification; the probe shows an increase in the sensitivity towards Cr6+ and decreases towards Cr3+, which is consistent with their toxicity characteristics, benefiting the assessment of total Cr toxicity. The proposed probe achieves considerable two-channel (ultraviolet absorption spectrum and naked eye vision) detection of Cr3+ and Cr6+ providing wide linearity regions and low detection limits. Meanwhile, the results of the interference experiments and analysis of the real samples showed high selectivity and accuracy of the proposed method. With popularization, this method possesses great potential in environmental monitoring and control.