Sequential Hybrid Three-Dimensional Gas Chromatography with Accurate Mass Spectrometry: A Novel Tool for High-Resolution Characterization of Multicomponent Samples

Abstract

A novel sequential three-dimensional gas chromatography-high-resolution time-of-flight mass spectrometry (3D GC-accTOFMS) approach for profiling secondary metabolites in complex plant extracts is described. This integrated system incorporates a nonpolar first-dimension (D) separation step, prior to a microfluidic heart-cut (H/C) of a targeted region(s) to a cryogenic trapping device, directly followed by the rapid reinjection of a trapped solute into a polar second-dimension (D) column for multidimensional separation (GC-GC). For additional separation, the effluent from D can then be modulated according to a comprehensive 2D GC process (GC×GC), using an ionic liquid phase as a third-dimension (D) column, to produce a sequential GC-GC×GC separation. Thus, the unresolved or poorly resolved components, or regions that require further separation, can be precisely selected and rapidly transferred for additional separation on D orD columns, based on the greater separation realized by these steps. The described integrated system can be used in a number of modes, but one useful approach is to target specific classes of compounds for improved resolution. This is demonstrated through the separation and detection of the oxygenated sesquiterpenes in hop ( Humulus lupulus L.) essential oil and agarwood ( Aquilaria malaccensis) oleoresin. Improved resolution and peak capacity were illustrated through the progressive comparison of the tentatively identified components for GC-GC and GC-GC×GC methods. Relative standard deviations of intraday retentions ( t, t, and t) and peak areas of ≤0.01, 0.07, 0.71, and 7.5% were achieved. This analytical approach comprising three GC column selectivities, hyphenated with high-resolution TOFMS detection, should be a valuable adjunct for the improved characterization of complex plant samples, particularly in the area of plant metabolomics.

Chemical Profiles of Cultivated Agarwood Induced by Different Techniques

“…The alkaline mixture standard (C9–C40) were analyzed by the same program in GC-MS. The identification of components were assigned by the software GC-MS Postrun analysis (Shimadzu, Kyoto, Japan) by searching MS data and retention indices in National Institute of Standards and Technology (NIST, Washington DC, USA) and referring to previous reports [30,31]. Areas were recorded for all detectable peaks.…”

The Blossoming of Technology for the Analysis of Complex Aroma Bouquets—A Review on Flavour and Odorant Multidimensional and Comprehensive Gas Chromatography Applications

“…Banana Terra spirits were investigated for the first time by the authors, who identified 18 aroma-impact regions, and the main odorants found were 3-methylbutan-1-ol, 3-methylbutan-1-ol acetate, 2-phenylethylacetate and phenylethyl alcohol [89]. The same group also studied hop essential oil [12,52,83,84], identifying some of its impact odorants, such floral notes such as geraniol, linalool, β -ionone, and eugenol, and a compound responsible for woody/spicy aroma, 4-hydroxy- β -caryophyllene.…”

“…Marriott and co-workers [12,109] assessed the composition of Agarwood ( Aquilaria malaccensis ) oils through different multidimensional approaches. An integrated 3D GC-GC×GC system was used to improve the resolution of oxygenated sesquiterpenes of Agarwood (Figure 7).…”

“…Different design configurations are continually being explored for multidimensional GC techniques (Figure 1), using extended or integrated MDGC and GC×GC systems [8,9,10,11,12,13,14,15,16], coupled with different detectors, to address even more demanding separations and to accomplish greater separation. The overriding aim is to expand the separation capacity of the system.…”

“…Marriott and co-workers contributed a number of technical solutions and strategies to achieve better resolution of aroma compounds. Their successful implementation of a number of hybrid GC approaches in a single instrument [8,9,10,11,12] represents qualitative and quantitative developments to provide a convenient solution to overcome uncertainty of data correlation across multiple hyphenated systems. The use of cryogenic trapping and modulators, with flow switching explored by the group [17,18,19,20], allows the focussing and/or concentration of the volatile analytes in various modes of operation, which improves separation peak capacity and enhances the quality of analyte characterisation.…”