Evaluation of Conditions of Comprehensive Two-Dimensional Gas Chromatography That Yield a Near-Theoretical Maximum in Peak Capacity Gain

Author(s): Matthew S. Klee1, Jack Cochran2, Mark Merrick3, Leonid M. Blumberg4

  1. XO Associates LLC
  2. Restek Corporation
  3. LECO
  4. Advachrom

Published By: Journal of Chromatography A

Year of Publication: 2015

Link: http://www.sciencedirect.com/science/article/pii/S0021967315000771

Abstract:

The peak capacity gain (Gn) of a GCxGC system is the ratio of the system peak capacity to that of an optimized one-dimensional GC analysis lasting the same time and providing the same detection limit. A near-theoretical maximum in Gn has been experimentally demonstrated in GCxGC-TOF based on a 60 m x 0.25 mm primary column. It was found that Gn was close to 9 compared to the theoretical maximum of about 11 for this system. A six-sigma peak capacity of 4500 was obtained during an 80 min heating ramp from 50 °C to 320 °C. Using peak deconvolution, 2242 individual peaks were determined in a Las Vegas runoff water sample. This is the first definitive experimental demonstration known to us of an order-of-magnitude Gn. The key factors enabling this gain were: relatively sharp (about 20 ms at half height) reinjection pulses into the secondary column, relatively long (60 m) primary column, the same diameters in primary and secondary columns, relatively low retention factor at the end of the secondary analysis (k ≅ 5 instead of 15, optimal for ideal conditions), optimum flow rate in both columns, and helium (rather than hydrogen) used as the carrier gas. The latter, while making the analysis 65% longer than if using H2, was a better match to the reinjection bandwidth and cycle time.

 

 

Eight Tips for Easy GC×GC

Author(s): Jack Cochran
Restek Corporation

Published By: The Analytical Scientist

Issue: #18 (0714)

Year of Publication: 2014

Link: https://theanalyticalscientist.com/issues/0714/eight-tips-for-easy-gcxgc/

Abstract: Comprehensive two-dimensional gas chromatography is often presented as extremely complicated. It isn’t. Here is some simple advice to help attract more users to the benefits.

Comprehensive Two-Dimensional Gas Chromatography With a Multi-Capillary Second Dimension: A New Column-Set Format for Simultaneous Optimum Linear Velocity Operation

Author(s): Daniela Peroni1, Andjoe A.S. Sampat1, Wil van Egmond2, Sjaak de Koning3, Jack Cochran4, Roy Lautamo4, Hans-Gerd Janssen1,5

1. University of Amsterdam, 2. NLISIS, 3. LECO Corporation, 4. Restek Corporation, 5. Advanced Measurement and Data Modelling, Unilever

Published By: Journal of Chromatography A

Issue: tbd

Year of Publication: 2013

Link: http://www.sciencedirect.com/science/article/pii/S0021967313011989

Abstract: Comprehensive two-dimensional gas chromatography (GCxGC) suffers from the impossibility to operate both dimensions at their optimum carrier gas velocity at the same time due to the different inner diameters of the columns typically employed. The use of multiple parallel capillary columns in the second dimension (GC x multi-GC) is studied as a means to achieve simultaneous optimum-velocity operation. A programme written in Microsoft Excel® was developed to calculate the efficiency of the two dimensions in GC x multi-GC for different numbers of columns in the second dimension. With the aid of this programme the appropriate number of columns was selected. Columns with maximum repeatability were specifically manufactured to grand suitable performance, i.e. to avoid band broadening effects caused by inter-column variations. 1D-GC experiments were carried out on the columns separately and combined in parallel. The performance of the parallel column set was consistent with that of the individual columns, with over 9100 plates generated (approximately 10,000 plates/m). A GC x multi-GC set-up was successfully installed. Model experiments proved the possibility to operate both dimensions at their optimum linear velocity simultaneously. The suitability of the novel second dimension column format to perform multidimensional separations was also shown for a number of selected applications.

Fingerprinting Crude Oils and Tarballs using Biomarkers and Comprehensive Two-Dimensional Gas Chromatography

Author(s): Michelle Misselwitz, Jack Cochran, Chris English, and Barry Burger
Restek Corporation

Published By: Restek Corporation

Year of Publication: 2013

Link: http://www.restek.com/Technical-Resources/Technical-Library/Petroleum-Petrochemical/petro_PCAN1789-UNV

Abstract: Petroleum biomarkers are “molecular fossils” that can be analyzed with gas chromatography to fingerprint crude oil. Fingerprints can then be used to determine the source oil for an oil spill or highly weathered tarballs. This unique fingerprint is developed by evaluating several ratios of key biomarkers, such as steranes and hopanes. Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GCxGC-TOFMS) was used to evaluate biomarker ratios in several crude oils from various regions and also in tarballs that washed ashore on the gulf coast of Florida up to a year after the Deepwater Horizon oil spill of 2010. While one-dimensional GC-MS is often used for this analysis, the power of GCxGC provides enhanced specificity and peak capacity with increased resolving power that can separate diagnostic biomarkers from potential isobaric interferences. Also, GCxGC provides a structured chromatogram, which allows compound identification that would be impossible with GC-MS due to the complexity of crude oil. In this study, using 43 different biomarker ratios from GCxGC-TOFMS analysis, we identified one tarball from a Florida beach that was a possible match to oil from a broken riser pipe collected via an underwater robot during the Deepwater Horizon oil spill. Others were considered non-matches.