Sensitive volatile phenol analysis in Chinese Baijiu using direct injection-on-line trapping coupled with gas chromatography-tandem mass spectrometry (LVI-Ttrap-GC-MS/MS)

Volatile phenols, including guaiacol, 4-methyguaiacol, 4-ethylguaiacol, eugenol, phenol, o-cresol, p-cresol, m-cresol, 4-ethylphenol and 2,6-dimethylphenol , are important aroma compounds in Chinese Baijiu. A fast and sensitive quantitation method of volatile phenols in Baijiu was developed using direct large-volume injection-on-line trapping coupled with - gas chromatography - triple quadrupole mass spectrometry (LVI-T_trap-GC-MS/MS). Stable isotope phenolic compounds were mixed with the Baijiu, and the sample (20 μL) was directly injected into a MMI injector without any further sample preparation and concentration. The removal of ethanol and enrichment of volatile phenols were achieved with on-line Tenax resins packed in the split/splitless liner under solvent-vent mode. The initial trapping temperature, vent flow, vent time, final temperature, vent pressure, desorption time, desorption flow, and other parameters were optimized. The developed method had excellent correlation coefficients with R² in the range of 0.9994-0.9999 for all volatile phenols ranging from 0.7 to 530 μg/L. Recoveries under three concentrations (10, 50, and 100 μg/L) were from 87-115% in strong, light, and sauce aroma-type baijiu matrix. The method represented a standard deviation in three concentrations (10, 50, and 100 μg/L) less than 4% for all volatile phenols. The limit of quantification (LOQs) in baijiu samples was lower than 0.7 μg/L. The method was further applied to analyze the distribution of volatile phenols in various Chinese baijiu samples.. The results showed that nongxiangxing baijiu had high concentrations of p-cresol and phenol, followed by sauce aroma-type baijiu and others. p-Cresol, 4-ethylguaiacol, and 4-ethylphenol, were important volatile phenolic compounds in Chinese baijiu according to their detected sensory threshold and calculated OAVs.