3-Hydroxy-2-naphthohydrazide: A Commercially Available Compound for Fluorescence Sensing of Ortho-Vanillin and Vanillin

Vanillin and ortho-vanillin are the most important flavoring additives used in the food industry at a large scale. Herein, the aggregation-induced emission (AIE) behavior of commercially available 3-hydroxy-2-naphthohydrazide (3HN) was explored and applied for the detection of vanillin and ortho-vanillin. The weakly fluorescent 3HN in DMSO showed fluorescence enhancement at 500 nm with the increase in HEPES or PBS buffer (pH 7.4) fractions in DMSO. The 3HN in DMSO containing 30% HEPES buffer is used as Probe 1 for the selective detection of ortho-vanillin. Probe 1 showed a new fluorescence emission at 415 nm for ortho-vanillin without altering the probe emission at 500 nm. With high specificity, Probe 1 can detect ortho-vanillin down to 0.3 μM. In contrast, 3HN in DMSO containing 20% PBS buffer is used as Probe 2 for the selective turn-off detection of vanillin. The green fluorescence emission of Probe 2 at 500 nm is selectively quenched by vanillin with a detection limit of 0.8 μM. Finally, the analytical novelty of the developed probes was examined by quantifying ortho-vanillin and vanillin in spiked food samples with good recovery percentages.