A simple and sensitive assay for the determination of nitrite using folic acid as the fluorescent probe

Nitrite, which poses a serious threat to human health despite finding wide application in industry and architecture, has aroused more and more attention. In this study, a simple yet sensitive and selective fluorimetric assay for the determination of trace nitrite using folic acid as the probe has been established. Folic acid exhibited weak fluorescence in strong acidic conditions. However, a dramatic enhancement in the fluorescence intensity occurred when folic acid was exposed to ultraviolet (UV) radiation with the addition of nitrite. In particular, the UV radiation time played a vital role. Furthermore, the fluorescence intensity could reach the maximum by adjusting the pH value of the solution within a certain range. The excellent selectivity was attributed to the specificity of diazo reaction. The turn-on fluorescence strategy endows this assay with high sensitivity down to the 18 nM detection limit and a wide detection range from 50 nM to 32 mu M. Finally, this assay was applied to detect nitrite in real samples with satisfactory results.