Synthesis of highly fluorescent carbon dots from spices for determination of sunset yellow in beverages

Sunset yellow is synthetic azo dye used to color food products in food industry. Sunset yellow has no toxicity if taken in permissible amounts. The daily acceptable intake of dye is 2.5 mg/Kg as per WHO health guidelines. Above the permissible limit, sunset yellow dye is dangerous posing serious threat to human health worldwide leading to multiorgan (gastric, immunological, neurological) failure related symptoms especially in children can cause DNA damage. Other symptoms include ADHD like behavior in children. This has led to Food Safety Agencies to regulate permissible limit of sunset yellow in food products. Therefore, it is necessary to develop method for the removal of dye in different foodstuffs. Nano-sized fluorescent carbon dots (CDs) have been synthesized from spices (fenugreek, cloves and cumin) under hydrothermal conditions. Characterization has been done through UV–Vis, TEM, FT-IR and XRD spectroscopy. Results reveals that CDs possess high water solubility due to surface rich hydroxyl groups, excellent photo-stability and are non-toxic. There was strong quenching of fluorescence intensity (F0/F) of CDs in the presence of sunset yellow food dye. Further, there was no effect to fluorescence intensity with the presence of interferences. The linear concentration range obtained was 0.25 µM-60.0 µM with the detection limit of 0.20 µM. The calculated relative standard deviation (RSD) for determination of sunset yellow was found to be 0.21%. The present method was applied successfully for the determination of sunset yellow dye in various food samples with recovery values of 99.8 and 103.6%.