2D GAS CHROMATOGRAPHY
Comprehensive two-dimensional gas chromatography (GC×GC) is a multidimensional gas chromatographic technique used in a variety of different industries and research applications.
HISTORY OF GC×GC
The first reported use of a two dimensional gas-liquid chromatographic system was reported in the journal Analytical Chemistry by Simmons and Snyder, 1958. This system connected two gas-liquid chromatographic columns with a heart-cut system such that a portion of the effluent from the first column was diverted to a detector, while the remainder of the effluent passed on to a second column with a different separation phase.
Comprehensive two-dimensional gas chromatography was invented by the late Professor John Bruce Phillips of Southern Illinois University at Carbondale and his then graduate student, Dr. Zaiyou Liu. The term "comprehensive" indicates that the entire sample injected into the GC×GC system exists to the same detector.
Phillips Prize was created in honor of John Phillip and his contribution to contribution to analytical chemistry. This prize is presented every other year to researchers who provide novel contributions to the development and application of GC×GC.
THEORY OF GC×GC
Gas Chromatography (GC) works by separating complex, molecular mixtures into resolvable components using a capillary column coated with a stationary phase. The elution of compounds is based on the specific volatility and polarizability interactions that a compound has toward a column’s stationary phase. By interfacing a GC with a flame ionization detector (FID) or mass spectrometer (MS), it becomes possible to compare the diversity and abundance of specific molecular constituents in a GC amendable chemical mixture. However, this method is limited by the compositional complexity of the mixture being analyzed and by the detectable mass range of the capillary column. Due to the complex nature of some natural samples, liquid chromatographic separations are first performed to produce a less chemically complex subfraction. Unfortunately, even with these added steps and instrumental interfaces, such as MS, the complete compositional characterization of a subfraction is not always possible. Subsequently, even under the best conditions, only a limited number of well-resolved compounds can be identified and quantified within a discrete mass range of any reservoir fluid. The vast amount of molecular complexity is ignored.
GC×GC greatly improves the resolving power of a gas chromatograph by linking a second column containing a different stationary phase (termed second dimension column) to the first column (termed first dimension column) via a modulator. The modulator temporally halts, focuses, and concentrates the effluent leaving the first dimension column to produce discrete packets of effluent that are launched onto the second dimension column. The two chromatographic columns are selected to separate analytes by such orthogonal physical properties as volatility and polarity. In this way, the number of resolvable compounds residing in a complex chemical mixture is greatly enhanced.
NOTE: Some of the samples, GC×GC chromatograms, and figures represented here were obtained or were first produced in Chris Reddy's organic geochemistry laboratory by Robert Nelson at Woods Hole Oceanographic Institution. Their incorporation here is to their generous contribution for the education of all.
Cryogenic modulation involves the temporary freezing of a small packet of effluent onto a capillary column and then heating it so that the packet can be released into a second column This process is repeated at a given rate referred to as the modulation frequency.
The loop jet modulator uses a single hot and cold jet to doubly focus a packet of effluent of given modulation frequency before releasing it into the next column.
An example of the initial 1D data output stream from the detector. As one zooms closer into the chromatogram, the resolution of the separation created by second dimension column becomes evident.
The following is a quantitative example of the enhanced peak capacity of GCxGC, borrowed from a lecture by John Demanja.
GC X GC DATA PROCESSING
Once a GC×GC run has finished the data must be parsed to the modulation frequency configured based on the column configuration, GC conditions, and chemistry of the effluent being analyzed.
Additional data processing procedures are done with the aid of soft-ware packages such as ChromaToF© and GC-Image©. These processes include visualization adjustments, compound identification, and data reduction applications.
The slides above illustrate how the data processing works.
Arey, J. Samuel; Nelson, Robert K.; Xu, Li; Reddy, Christopher M. Using Comprehensive Two - Dimensional Gas Chromatography Retention Indices To Estimate Environmental Partitioning Properties for a Complete Set of Diesel Fuel Hydrocarbons. Analytical Chemistry (2005), 77(22), 7172-7182.
Arey J Samuel; Nelson Robert K; Reddy Christopher M Disentangling oil weathering using GC x GC. 1. chromatogram analysis. Environmental science & technology (2007), 41(16), 5738-46.
Arey J Samuel; Nelson Robert K; Plata Desiree L; Reddy Christopher M Disentangling oil weathering using GC x GC. 2. Mass transfer calculations. Environmental science & technology (2007), 41(16), 5747-55.
Beens, Jan; Boelens, Hans; Tijssen, Robert; Blomberg, Jan. Quantitative aspects of comprehensive two - dimensional gas chromatography (GC ´ GC). Journal of High Resolution Chromatography (1998), 21(1), 47-54.
Dimandja, Jean-Marie D.; Stanfill, Stephen B.; Grainger, James; Patterson, Donald G., Jr. Application of comprehensive two - dimensional gas chromatography (GC ´ GC) to the qualitative analysis of essential oils. Journal of High Resolution Chromatography (2000), 23(3), 208-214.
Frysinger Glenn S; Gaines Richard B; Xu Li; Reddy Christopher M Resolving the unresolved complex mixture in petroleum-contaminated sediments. Environmental science & technology (2003), 37(8), 1653-62.
Frysinger, Glenn S.; Gaines, Richard B. Separation and identification of petroleum biomarkers by comprehensive two - dimensional gas chromatography. Journal of Separation Science (2001), 24(2), 87-96.
Gaines, Richard B.; Frysinger, Glenn S.; Hendrick-Smith, Martha S.; Stuart, James D. Oil Spill Source Identification by Comprehensive Two - Dimensional Gas Chromatography. Environmental Science and Technology (1999), 33(12), 2106-2112.
Grainger, James; Green, Vaughn; Liu, Zaiyou; Barr, John; McClure, Cheryl; Patterson, Donald G., Jr.; Holland, John F.; Gardner, Ben D. Analysis of environmental toxicant group components by time-compressed gas chromatography and comprehensive two - dimensional gas chromatography coupled with high resolution mass spectrometry and time of flight mass spectrometry. Organohalogen Compounds (1996), 27 354-359.
Hoggard Jamin C; Synovec Robert E Parallel factor analysis (PARAFAC) of target analytes in GC x GC-TOFMS data: automated selection of a model with an appropriate number of factors. Analytical chemistry (2007), 79(4), 1611-9.
Liu, Zaiyou; Phillips, John B. Comprehensive two - dimensional gas chromatography using an on-column thermal modulator interface. Journal of Chromatographic Science (1991), 29(6), 227-31.
Phillips, John B.; Xu, Jingzhen. Environmental applications of comprehensive two - dimensional gas chromatography. Organohalogen Compounds (1997), 31 199-202.
Phillips, John B.; Gaines, Richard B.; Blomberg, Jan; Van Der Wielen, Frans W. M.; Dimandja, Jean-Marie; Green, Vaughn; Granger, James; Patterson, Don; Racovalis, Laell; De Geus, Henk-Jan; De Boer, Jacob; Haglund, Peter; Lipsky, John; Sinha, Veena; Ledford, Edward B., Jr. A robust thermal modulator for comprehensive two - dimensional gas chromatography. Journal of High Resolution Chromatography (1999), 22(1), 3-10.
Reddy Christopher M; Eglinton Timothy I; Hounshell Aubrey; White Helen K; Xu Li; Gaines Richard B; Frysinger Glenn S The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments. Environmental science & technology (2002), 36(22), 4754-60.
Seeley, John V.; Kramp, Frederick J.; Sharpe, Kristopher S.; Seeley, Stacy K. Characterization of gaseous mixtures of organic compounds with dual-secondary column comprehensive two - dimensional gas chromatography (GC ´ 2GC). Journal of Separation Science (2002), 25(1/2), 53-59.
Tobias, Herbert J.; Sacks, Gavin L.; Zhang, Ying; Brenna, J. Thomas. Comprehensive Two - Dimensional Gas Chromatography Combustion Isotope Ratio Mass Spectrometry. Analytical Chemistry (Washington, DC, United States) (2008), 80(22), 8613-8621.
Venkatramani, Cadapakam J.; Phillips, John B. Comprehensive two - dimensional gas chromatography applied to the analysis of complex mixtures. Journal of Microcolumn Separations (1993), 5(6), 511-16.
Ventura, Gregory T.; Kenig, Fabien; Reddy, Christopher M.; Schieber, Juergen; Frysinger, Glenn S.; Nelson, Robert K.; Dinel, Etienne; Gaines, Richard B.; Schaeffer, Philippe. Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere. Proceedings of the National Academy of Sciences of the United States of America (2007), 104(36), 14260-14265.
Ventura, Gregory T.; Kenig, Fabien; Reddy, Christopher M.; Frysinger, Glenn S.; Nelson, Robert K.; Van Mooy, Ben; Gaines, Richard B. Analysis of unresolved complex mixtures of hydrocarbons extracted from Late Archean sediments by comprehensive two - dimensional gas chromatography (GC´ GC). Organic Geochemistry (2008), 39(7), 846-867.