Comprehensive Two-Dimensional Gas Chromatography with Mass Spectrometry: Toward a Super-Resolved Separation Technique

Abstract

A data interpretation and processing approach for improved compound identification and data presentation in comprehensive two-dimensional gas chromatography (GC×GC) is described. A footprint peak of a compound in 2D space can be represented by a centroid or peak apex, similar to the data-reduced histogram spectra used in mass spectrometry. The workflow was demonstrated on data from GC×GC–TOFMS. Peaks in a modulated chromatogram were initially detected by conventional chromatographic integration, followed by a curve-fitting approach, which interpolated high-precision, absolute retention times for all modulated peaks. First dimension retention time (1 t R) was obtained by using an exponentially modified Gaussian (EMG) fitting model for near-Gaussian distributed subpeaks, polynomial fitting for highly asymmetrical peaks, and parabolic fitting for under-sampled peaks, which allows determination of a precise 1 t R, considering the dwell-time arising from modulation and 2 t R. Area summation of the modulated peaks belonging to the same compound was then performed to yield the total peak area. Each compound in the GC×GC–MS result was then represented by its position at the intersecting coordinates, (1 t R, 2 t R), in the 2D separation plane, having a height of the same magnitude as the total component summed area. This results in a novel and uncluttered GC×GC output convention based on the scripted total ion chromatogram (TIC) data with precise 1 t R, 2 t R, and area. Comparison between the contour plots from the scripted and conventional TIC revealed improved data presentation, accompanied by an apparent enhanced resolution. The described approach was applied to the identification of 177 aroma compounds from peaches as indicators of fruit quality.

Comprehensive two-dimensional gas chromatography with mass spectrometry: an advanced bioanalytical technique for clinical metabolomics studies

“…45 The clever cross-coupling of GC×GC with MS empowers bioanalysts with a high-resolution analytical technology that provides unsurpassed molecular separation and informing power. 46 For untargeted metabolite profiling of a complex biological system, known and unknown metabolites normally cover a wide range of structures with different intrinsic physicochemical properties. MS detection further refines solute identification by providing mass-spectrum information of the chromatographically isolated “pure” bands/peaks, normally with reduced background interference signals.…”

Unveiling Chemical Cues of Insect-Tree and Insect-Insect Interactions for the Eucalyptus Weevil and Its Egg Parasitoid by Multidimensional Gas Chromatographic Methods

“…On the 2 D column, the collected sample from the modulator needs to be eluted before the following collected sample is released from the modulator to minimize the occurrence of wrap-around [42,43]. Due to the fast elution in the 2 D, the detector must have a high-speed acquisition rate (at least 50 Hz), especially due to the resulting narrow peaks-peaks width of 50-300 ms at the base [44]. When the GC×GC is applied, an increase in the peak capacity (n c ) occurs equal to the product of the peak capacity of both 1 D and 2 D (n c1 × n c2 ) [44].…”

“…Due to the fast elution in the 2 D, the detector must have a high-speed acquisition rate (at least 50 Hz), especially due to the resulting narrow peaks-peaks width of 50-300 ms at the base [44]. When the GC×GC is applied, an increase in the peak capacity (n c ) occurs equal to the product of the peak capacity of both 1 D and 2 D (n c1 × n c2 ) [44]. The 1 D has a longer length and a higher n c value, in contrast to 2 D, which needs to have a shorter length to permit a very fast elution, so that the two-dimensional run is completed within practically the same time as the 1 D run [44].…”

“…When the GC×GC is applied, an increase in the peak capacity (n c ) occurs equal to the product of the peak capacity of both 1 D and 2 D (n c1 × n c2 ) [44]. The 1 D has a longer length and a higher n c value, in contrast to 2 D, which needs to have a shorter length to permit a very fast elution, so that the two-dimensional run is completed within practically the same time as the 1 D run [44]. Hence, in order to further unravel the composition of the samples and to detect chromatographic co-elutions that may still hide the bio-active compounds from the GC/MS-EAD analysis, GC×GC-FID qualitative and semi-quantitative experiments were also performed on a polar × non-polar column set, where the first polar column is equivalent to the WAX column used in the GC/MS-EAD experiments.…”

Separation Multidimensionality for Improved Sample Characterization—Is It Worth the Effort?

“…Again, this capability may not be accomplished with a low-resolution 1D method. Additionally, GC×GC data can be presented as super-resolved data using centroiding . The data are plotted in three-dimensional (3D) space: 1 t R , 2 t R , and compound abundance.…”