Ratiometric fluorescence detection of tetramethylpyrazine in complex matrices using a Tb-EDTA probe based on LMCT modulation

Background The accurate detection of 2,3,5,6-tetramethylpyrazine (TMP) in complex matrices is significant for food quality control and biomedical analysis. Despite this need, a dedicated optical sensing platform for TMP has not been reported to date. Results Here, we present a novel ratiometric fluorescent probe based on a Tb–EDTA complex, which introduces a sensing strategy founded on coordination-induced modulation of the ligand-to-metal charge transfer (LMCT) process. Specific coordination of TMP's pyrazine nitrogen atoms to the Tb 3+ center results in a characteristic ratiometric response: quenching of the emission at 548 nm and concomitant enhancement at 650 nm. The probe exhibits excellent analytical performance with a linear range of 0.1―40 μM, a detection limit of 0.038 μM, and high selectivity over structurally similar interferents. Its practical applicability is demonstrated by reliable quantification of TMP in real samples, including sauce-flavor Baijiu, sake, and human urine, with recoveries of 94.54–104.82% and relative standard deviations below 10.57%. Significance This work establishes a pioneering optical sensing approach for TMP detection, providing a valuable analytical tool for flavor assessment in alcoholic beverages and pharmacological monitoring in biological systems.