| dc.description.abstract | Comprehensive two-dimensional chromatography (GC × GC) is inherited with high peak capacity that dramatically improves separation resolution and alleviates the co-elution problem for complex samples (such as fuels or essential oils), making GC × GC a main stream technique in modern chromatography.
When coupling with mass spectrometry it becomes a powerful qualitative and quantitative tool, particularly if time-of-flight mass spectrometry (TOFMS) is chosen due to its fast data acquisition rate (200Hz) and high mass resolution, making the GC × GC – TOFMS technique superior to other GC detection methods (e.g., flame ionization detection; FID). However, because of the high cost in purchase and maintenance, GC × GC – TOFMS is generally out of reach for average budget-concerned laboratories. As a result, this research is attempted to transform a regular GC into a GC × GC setup using a Deans switch as the valve-based modulator and both FID and quadrupole mass spectrometry for detection (GC × GC – FID/qMS). Although the data acquisition rate for qMS is too low for normal GC × GC use, its role in this study is only limited to structural identification, whereas quantitation is performed by FID to acquire the complete GC × GC contour.
Our GC × GC - FID/qMS system used a DB-1 column (60 m × 0.25 mm i.d. × 1 μm d.f.) as the first dimensional (1D) column and a DB-1701 column (1 m × 0.25 mm i.d. × 0.5 μm d.f.) as the second dimensional (2D) column to reveal the orthogonality of zero-polarity vs. mid-polarity. By searching with the NIST (version 08) library, 7 compounds out of 34 in the standard mixture, including alkanes, alcohols, esters, and ketones, were able to be identified. Quality assurance of linearity and precision were performed for the target compounds. For instance, the five alkanes, i.e., n-octane, n-nonane, n-decane, n-undecane, and n-dodecane, showed linearity (R2) better than 0.98 in the concentration range of 10 - 100 ppm and the relative standard deviations (RSDs) better than 0.89% (n = 5). With this newly developed GC × GC - FID/qMS method, the fingerprints of liquor and gasoline samples were successfully obtained.
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