Detection of congeners and contaminants in commercial and homemade alcoholic beverages under varying temperatures using metal-phenolic film-coated quartz crystal microbalances.

Consumption of cheap, adulterated alcohol containing high congener levels (e.g., aldehydes, esters, fusel alcohols, methanol) takes a major socioeconomic toll, highlighting the need for on-site analysis. Handheld chemical profiling of spirits is feasible via Raman spectrometry, but its applicability is limited by dark packaging as well as unverified accuracy for low-alcoholic products and homemade distillates. To address this shortcoming, we examine the resonance behavior of metal-phenolic film-coated quartz crystal microbalances in response to the saturated vapor of five commercial or homemade fermented and distilled beverages (beer, white wine, red wine, whiskey and grape brandy). Validated across 270 trials, the sensor demonstrated superior repeatability in chemical characterization of the drinks at mild and room temperatures, maintaining minimal error of ~ 0.2-3.6%. Competitive vapor sorption leads to non-linear quantitative detection upon injection of 0.25-2.5 mL methanol into the alcoholic drinks. Under optimal temperature of the beer and grape brandy (6-16 °C), however, the sensor demonstrates a linear relationship with increasing methanol levels. It achieves a detection limit of ~ 0.13 g/100 mL, a value 7.4 times lower than the current EU permissible dose. This outcome emphasizes the resilience of our technology in point-of-use quality assessment of beverages, counteracting counterfeit alcohol trading.