Turn-off fluorescent nanoprobe based on carbon dots synthesised by UV/H2O2 advanced oxidation for the detection of bisphenol A in canned foods

A novel assay was developed based on a turn-off fluorescent probe using the in situ generation of carbon dots (CDs) by means of UV/H2O2 advanced oxidation of carbohydrates for the detection of bisphenol A (BPA) in food. Different parameters involved in the synthesis of CDs for the direct recognition of BPA have been optimised and a sensing mechanism is outlined. The presence of H2O2 during CD synthesis causes a fluorescence enhancement due to the action of highly oxidant HO<middle dot> radicals formed throughout the photochemical reaction. Phenolic compounds such as BPA can be easily degraded by the UV/H2O2 oxidation process, acting as a HO<middle dot> free radical scavengers. This results in a decrease in the fluorescence that can be related to the BPA concentration. Under optimal conditions, a detection limit of 15 mu g/kg of BPA and a quantification limit of 46 mu g/kg of BPA in food samples were obtained. The repeatability and reproducibility, expressed as relative standard deviation and obtained for two concentration levels (30 mu g/kg and 200 mu g/kg, n = 5), were less than 2.0% and 6.4%, respectively. The proposed procedure was applied to the analysis of five samples of canned foods (sweet corn, peas, mushrooms, cockles and natural tuna), obtaining concentrations in the range 29.8-49.9 mu g/kg of sample. Recovery studies were conducted at two concentration levels (100 and 400 mu g BPA/kg of sample), resulting in recoveries in the range 99-101%. Method validation against two certified reference materials was also successfully performed. The experimental results demonstrate that the novel approach is suitable for the detection and quantification of BPA in canned foods.