Edible gelatin-based hydrosol for optical detection of metal ions in water

High concentration of metallic compounds in water poses a serious threat to human health and aquatic ecosystems becoming a global environmental issue in present society. This study presents a simple method for detecting Fe³⁺, Sn²⁺, and Cr⁶⁺ ions using commercial edible gelatin as a molecular probe. Based on the absorbance- and luminescence-based optical response, the eco-friendly label-free method demonstrated the detection limits of 0.81 µM/1.7 µM, 2.39 µM/3.19 µM and 0.84 µM. Metal-binding properties are explained as the synergistic effect between the functional groups on the gelatin molecule chain and the physicochemical properties of the metal ion. Competitive absorbance measurements, using a bi-component water sample, were performed to gain insights into the governing factors that influence the prevailing metal affinity of gelatin in complex water matrices. Apart from environmentally friendly and sustainable attributes, the ease and simplicity of preparing the gelatin-based hydrosols make them a potential biomaterial for real applications in metal ion sensing.