Fluorescent azamonardine probe for “turn-off” detection of chromium (VI) and “turn-on” detection of ascorbic acid based on inner filter effect

In this study, a facile water-soluble fluorescent azamonardine probe is directly prepared by the reaction of dopamine and resorcinol under alkaline conditions (pH 11.0). Under the excitation light of 420 nm, it emits fluorescence at 460 nm. Since chromium(VI) (Cr 6+ ) has absorbance from 300 to 450 nm, fluorescence of this probe gets decreased in the presence of Cr 6+ based on the inner filter effect. It is worth noting that Cr 6+ can be reduced to Cr 3+ by ascorbic acid (AA) and the inner filter effect is inhibted in the presence of both AA and Cr 6+ . Accordingly the fluorescence is turned on again. Therefore this probe is utilized in fluorescent “turn-off” detection of Cr 6+ in the range of 15–600 μM and “turn-on” detection of AA in the range of 0.2–1.5 mM. It has high selectivity in Cr 6+ and AA detection towards other metal ions or other substances such as glutathione or cysteine. Meanwhile, when it is utilized to detect Cr 6+ in lake water and AA in serum sample, the calculated average recoveries are from 97.4% to 103.8% and from 98.8% to 101.5%, with the relative standard deviations (RSDs) lower than 5%.