Integrated Data Analysis Making Use of the Total Information from Gas Chromatography and High-Resolution Time-of-Flight Mass Spectrometry to Identify Qualitative Differences Between Two Whisky Samples
Analysis of complex mixtures with gas chromatography coupled with high-resolution time-of-flight mass spectrometry (GC-HRTOFMS) can produce a large amount of data. A new software program was recently reported that integrates all of the available mass spectrometric information from GC-HRTOFMS analysis into a concise report. New capabilities have now been added to the software to incorporate retention index data and to identify differences between two samples.
Two Scotch whisky samples were sampled by solid-phase microextraction (SPME) and analyzed by GC-HRTOFMS. One of the two whisky samples (Sample B) was identical to the other sample (Sample A) except for an additional six months storage in sherry casks. Both electron ionization (EI) and chemical ionization (CI) data were obtained using a new GC-time-of-flight mass spectrometer system (JEOL AccuTOF GC-Alpha) with enhanced resolving power and mass accuracy. Statistical analysis of replicate measurements of the whisky samples was carried out with a new software program (msFineAnalysis version 3.2) to identify and assign differences between the samples.
There were 124 peaks detected in the two whiskies. Thirteen compounds were detected with a relative peak area greater than 0.05% that were present in greater amounts in the whisky that was stored in sherry casks for an additional 6 months. Ten of these compounds were identified by the software with high confidence, two were identified as isomers with close retention indices, and one was identified interactively.
The software identified small differences between the two samples that resulted from sherry cask aging. Because all of the information available from the hard and soft ionization analyses for each compound is summarized in a concise integrated report, the operator can rapidly determine the level of confidence for each assignment and inspect the information for compounds that are not present in the database.