The Need for Two-Dimensional Gas Chromatography: Extent of Overlap in One-Dimensional Gas Chromatograms

Davis, Joe M.; Samuel, Clint

doi:10.1002/(sici)1521-4168(20000301)23:3<235::aid-jhrc235>3.3.co;2-9

Cited by 11 publications

(17 citation statements)

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“…30 So thermal degradation in inert atmosphere directly correlates with the flame property of polymer, especially for the condensed-phase mechanism category. Although a substantial number of works 22,[31][32][33][34][35] have paid attention to the thermal degradation mechanism of PC in inert atmosphere, controversies on the mechanisms are still existing. The representative controversies are whether xanthone functional group is generated and whether the chain scission of isopropylidene linkage occurs first during thermal degradation.…”

Section: Kinetics Analysismentioning

confidence: 99%

A polycarbonate/magnesium oxide nanocomposite with high flame retardancy

Dong

Gao

Ding

et al. 2011

J of Applied Polymer Sci

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A new flame retardant polycarbonate/magnesium oxide (PC/MgO) nanocomposite, with high flame retardancy was developed by melt compounding. The effect of MgO to the flame retardancy, thermal property, and thermal degradation kinetics were investigated. Limited oxygen index (LOI) test revealed that a little amount of MgO (2 wt %) led to significant enhancement (LOI = 36.8) in flame retardancy. Thermogravimetric analysis results demonstrated that the onset temperature of degradation and temperature of maximum degradation rate decreased in both air and N2 atmosphere. Apparent activation energy was estimated via Flynn–Wall–Ozawa method. Three steps in the thermal degradation kinetics were observed after incorporation of MgO into the matrix and the additive raised activation energies of the composite in the full range except the initial stage. It was interpreted that the flame retardancy of PC was influenced by MgO through the following two aspects: on the one hand, MgO catalyzed the thermal-oxidative degradation and accelerated a thermal protection/mass loss barrier at burning surface; on the other hand, the filler decreased activation energies in the initial step and improved thermal stability in the final period.

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Section: Kinetics Analysismentioning

confidence: 99%

A polycarbonate/magnesium oxide nanocomposite with high flame retardancy

Dong

Gao

Ding

et al. 2011

J of Applied Polymer Sci

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“…This theory was first developed by Davis and Giddings [41] using Poisson statistics as the basis for the random distribution of retention times across the chromatogram to approximate the behavior of peaks in a "real" chromatogram. Davis and Samuel [42] argued that the peak capacity of 1D separations is woefully inadequate for the separation of complex mixtures in a comparison of predictions of the numbers of observable peaks to the numbers of observed peaks in simulated gas chromatograms of a variety of mixtures (i.e., PCB's, PAH's, fragrances, etc.) A simplified interpretation of their model for 1D separations (the reader is referred to ref.…”

Section: Theoretical Background For Multi-dimensional Chromatography mentioning

confidence: 99%

“…A simplified interpretation of their model for 1D separations (the reader is referred to ref. [42] for a more detailed discussion) which is adequate for the purpose of this discussion shows that on average the maximum fraction of the total peak capacity that can be manifested as chromatographic peaks is only 37%. A peak is simply a maximum in the signal and is comprised of the detector response to one or more chemical constituents.…”

Section: Theoretical Background For Multi-dimensional Chromatography mentioning

confidence: 99%

Fast, comprehensive two-dimensional liquid chromatography

Stoll

Xiao-ping

Wang

et al. 2007

Journal of Chromatography A

373

147

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The absolute need to improve the separating power of liquid chromatography, especially for multi-constituent biological samples, is becoming increasingly evident. In response, over the past few years, there has been a great deal of interest in the development of two-dimensional liquid chromatography (2DLC). Just as 1DLC is preferred to 1DGC based on its compatibility with biological materials we believe that ultimately 2DLC will be preferred to the much more highly developed 2DGC for such samples. The huge advantage of 2D chromatographic techniques over 1D methods is inherent in the tremendous potential increase in peak capacity (resolving power). This is especially true of comprehensive 2D chromatography wherein it is possible, under ideal conditions, to obtain a total peak capacity equal to the product of the peak capacities of the first and second dimension separations. However, the very long timescale (typically several hours to tens of hours) of comprehensive 2DLC is clearly its chief drawback. Recent advances in the use of higher temperatures to speed up isocratic and gradient elution liquid chromatography have been used to decrease the time needed to do the second dimension LC separation of 2DLC to about 20s for a full gradient elution run. Thus, fast, high temperature LC is becoming a very promising technique. Peak capacities of over 2000 and rates of peak capacity production of nearly 1 peak/s have been achieved. In consequence, many real samples showing more than 200 peaks with signal to noise ratios of better than 10:1 have been run in total times of under 30 min. This report is not intended to be a comprehensive review of 2DLC, but is deliberately focused on the issues involved in doing fast 2DLC by means of elevating the column temperature; however, many issues of broader applicability will be discussed.

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“…Nevertheless, we think that if two GCs of a mixture each follow one-dimensional SOT, then a column-switched cryofocused separation based on the same two phases will follow column-switching SOT. Since one-dimensional SOT describes overlap in predicted GCs of many mixtures on both polar and nonpolar phases, ,, our first two conclusions should apply to many column-switched separations.…”

Section: Discussionmentioning

confidence: 84%

Statistical-Overlap Theory of Column Switching in Gas Chromatography: Applications to Flavor and Fragrance Compounds

Samuel

Davis

2002

Anal. Chem.

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First-column gas chromatograms (GCs) of hundreds of flavor and fragrance compounds, and second-column GCs of specific regions of these GCs, are predicted using thermodynamic databases in commercial software. A statistical-overlap theory of column switching with cryogenic focusing then is developed by mimicking the predicted GCs by two kinds of Monte Carlo simulations. In the first kind, a probability distribution is calculated for the number of compounds in a region of the first-column GC, based on the number of observed peaks in the region, the number of observed peaks in the second-column GC, and the retention-time distributions and breadths of single-component peaks in both GCs. In the second kind, criteria are established for the theory's application. The theory is applied to 12 regions of first-column GCs. The theory predicts the number of compounds in all of them and shows that separation rarely is complete in second-column GCs, when 10 or more compounds are transferred between columns. The theory also rationalizes the tedious search required to find good separation conditions by showing that column-switching gas chromatography with cryogenic focusing is inherently statistical. The number of peaks in the second-column GC can be greater than, less than, or equal to the number of peaks in the relevant region of the first-column GC, and the good conditions sought by researchers to substantially improve separation correspond to favorable "rolls of the dice" found only by trial and error.

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The Need for Two-Dimensional Gas Chromatography: Extent of Overlap in One-Dimensional Gas Chromatograms

Cited by 11 publications

References 0 publications

A polycarbonate/magnesium oxide nanocomposite with high flame retardancy

A polycarbonate/magnesium oxide nanocomposite with high flame retardancy

Fast, comprehensive two-dimensional liquid chromatography

Statistical-Overlap Theory of Column Switching in Gas Chromatography: Applications to Flavor and Fragrance Compounds

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