Determination of Small Phenolic Compounds in Tequila by Liquid Chromatography with Ion Trap Mass Spectrometry Detection

Tequila is elaborated from Agave tequilana Weber blue variety and it is commercialized at different stages of aging. Chemical composition of this product has often been addressed; however, data on phenolic compounds are scarce. In this work, a high-performance liquid chromatography-electrospray ionization-ion trap mass spectrometry (HPLC-ESI-ITMS) procedure has been established for the determination of 34 small phenolic compounds. The combination of suitable separation conditions with extraction of chromatograms at individual m/z values has enabled for total analysis run of 17 min (11 min separation plus 6 min column cleaning/equilibration) with the detection limits in the range 1.28-75.0 mu g l(-1) (0.07-6.1 pmol on-column). Commercial tequilas analyzed included 6 white, 12 rested, and 4 aged. The following acids were found and quantified: gallic, procatechuic, 4-hydroxybenzoic, vanillic, syringic, homovanillic, 3-hydroxybenzoic, ferulic, salicylic, and benzoic. The white tequilas contained fewer compounds and lower total phenolics concentrations (range 36-408 mu g l(-1)) as compared to the rested and aged liquors (515-4,296 and 2,048-3,249 mu g l(-1), respectively). In the latter products, syringic, vanillic, procatechuic, and gallic acids were the most abundant, which indicates that maturation in wooden barrels is the main source of small phenolics in tequila. On the other part, homovanillic acid was found in all tequila types (medians for white, rested, and aged products 82, 153, and 162 mu g l(-1), respectively), suggesting that some phenolics may originate from the raw material or might be formed during liquor elaboration.