Ratiometric fluorescence determination of furfural in Chinese baijiu via schiff base formation and glutathione-triggered nucleophilic addition on N-CDs surface

A ratiometric fluorescence sensor was established for furfural detection. • The ratiometric sensor showed high selectivity and anti-interference. • The unique response is attributed to GSH-triggered addition to Schiff base on N -CDs. • The method was successfully applied to detect furfural in Chinese baijiu . Reliable methods for furfural (FUR) determination are significance for ensuring the food safety and quality control of Chinese baijiu . In this work, nitrogen-doped carbon dots ( N -CDs) were synthesized via a hydrothermal method using p -phenylenediamine ( p -PD) as the precursor. Taking advantage of the sequential reaction between the surface amino groups of N -CDs, FUR, and glutathione (GSH), a novel ratiometric fluorescence sensor was constructed. In the presence of FUR and GSH, the sensor exhibits a new blue emission peak at 433 nm, while the intrinsic red emission of N -CDs at 605 nm remains essentially unchanged, thereby generating a self-calibrated ratiometric signal ( I 433 /I 605 ). In particularly, this ratio increases linearly with FUR concentration increase, showing good linearity over two ranges (1.0−10 μmol/L and 10−140 μmol/L), with a detection limit as low as 80.75 nmol/L. Mechanistic investigations reveal that the sensing process involves Schiff base formation between FUR and the amino groups on N -CDs, followed by thiol nucleophilic addition of GSH to the C=N bond, these two steps together account for the emergence of the blue fluorescence. The method was successfully applied to the analysis of real baijiu samples, with spike recoveries ranging from 96.6% to 109.9%, and showing good prospects for practical application in alcoholic beverage analysis.