Facile quantification of free and total sulphur dioxide in beer using a flavylium-based fluorescent probe.

Accurate and convenient determination of free and total sulphur dioxide (SO) in beer is pivotal to guarantee the quality of beer, but the traditional assay methods are laborious, time-consuming, and dependent on experienced technician. In this study, we designed and synthesized a flavylium-based fluorescent probe Hy-S which exhibited selective response to SO under both acidic conditions (pH = 4.0) and basic conditions (pH = 9.0) with low detection limits of 0.076 mg/L and 0.041 mg/L, respectively. The real beer samples were directly assayed to obtain the free SO by the probe-based method while the samples were basified and diluted before spectral measurements to determine the total SO. Due to the advantages of fast response, convenience, accuracy and greenness, the probe-based method possesses great potential for quantification of both free and total SO in beer.