Temperature dependence of the resolution of diastereomeric isoprenoids in capillary GC. Experiments with 50 μm, 100 μm, and 250 μm i.d. Columns

Proot, M.; David, Frank; Sandra, Pat; Verzele, M.

doi:10.1002/jhrc.1240080814

Cited by 7 publications

(4 citation statements)

References 16 publications

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“…This could likely be overcome by retrofitting a multi-dimensional GC system. This would allow, for example, pristane and nC17 to be heart cut onto a second column, where they could be fully resolved (20). Sample analysis time could be lowered to <30 min or the minimum recycle time of the first column GC.…”

Section: Resultsmentioning

confidence: 99%

“…On some 95% methyl-, 5% phenylpolysiloxane capillary column phases (e.g., BPX5), pristane and nC17 coelute, which could allow a narrower heart cut to be taken. The second column could be operated using isothermal conditions where the peaks can be fully resolved on a nonpolar phase (20). This would improve the precision and time of the analysis, would be relatively inexpensive, and could be implemented on GC and GC-MS instruments.…”

Section: Resultsmentioning

confidence: 99%

“…Under normal gas chromatographic conditions, the diastereomers of each isoprenoid coelute as a single peak. They can, however, be partially resolved into two peaks by conventional instruments using methods developed by Maxwell and co-workers and later refined by others ( 15 , − . The first peak exclusively contains isomers with mature configurations, while the second peak contains the isomers with recent configurations () (Figure ).…”

Section: Introductionmentioning

confidence: 99%

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Determining the Extent of Biodegradation of Fuels Using the Diastereomers of Acyclic Isoprenoids

McIntyre

Harvey

Ferguson

et al. 2007

Environ. Sci. Technol.

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Improved testing and remediation procedures for sites contaminated with petroleum hydrocarbons are a priority in remote cold regions such as Antarctica, where costs are higher and remediation times are longer. Isoprenoid/n-alkane ratios are commonly used to determine the extent of biodegradation at low levels but are not useful once the n-alkanes have been removed. This study demonstrates how the diastereomers of the acyclic isoprenoids can be used to determine the extent of biodegradation in moderately biodegraded fuel in soils from a bioremediation trial at Casey Station, Antarctica. The biological diastereomers of pristane (meso; RS = SR) are depleted more rapidly during moderate biodegradation than the geological or mature diastereomers (RR and SS), and thus, the ratio of pristane diastereomers can determine the level of biodegradation. The statistical difference among mean diastereomer ratios for samples grouped according to the biodegradation scale and pristane/phytane ratios was highly significant. The ratios of norpristane and phytane diastereomers also change with biodegradation in a similar fashion, and different levels of sensitivity exist for each. Additional benefits are that the method can be performed on conventional gas chromatographs by non-specialist chemists and that the ratios are independent of evaporation and do not necessarily require a non-biodegraded reference (T0) sample. This study details a simple alternative method for determining the extent of biodegradation of fuels at moderate levels that can be applied to a wide range of petroleum products.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determining the Extent of Biodegradation of Fuels Using the Diastereomers of Acyclic Isoprenoids

McIntyre

Harvey

Ferguson

et al. 2007

Environ. Sci. Technol.

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“…Limited sample capacity translates into potential problems in detection. Truly efficient columns of this type allow the rapid separation of pristine and phytane which are important biomarkers in crude oil [24]. Isomer separations of this kind pose interesting challenges.…”

Section: Overlap In Gas Chromatography Causes and Potential Solutionsmentioning

confidence: 99%

Two-Dimensional Gas Chromatography. Concepts, Instrumentation, and Applications - Part 1: Fundamentals, Conventional Two-Dimensional Gas Chromatography, Selected Applications

Bertsch

1999

J. High Resol. Chromatogr.

186

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The writer of this review published in 1978 a three‐part article on two‐dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two‐dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two‐Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two‐Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need for complete separation. Some progress in the further development of conventional Two‐Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two‐dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two‐Dimensional Gas Chromatography, called comprehensive two‐dimensional GC, or GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two‐Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two‐Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed away shortly before this review was written. This contribution is dedicated to his memory.

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Multidimensional Gas Chromatography

Bertsch

2000

Encyclopedia of Analytical Chemistry

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Two‐dimensional gas chromatography (2‐D GC) is a logical extension of gas chromatography (GC) carried out on a single column. It provides physical resolution of components which are difficult to analyze by other means. Two different arrangements are possible in 2‐D GC. In the conventional mode, effluent fractions from the primary column are switched onto a secondary column of different polarity. In the comprehensive mode, the entire effluent from the primary column is examined by the secondary column. The major advantage of 2‐D GC is the enhancement of peak capacity. Statistical methods of overlap theories predict severe limitations of the resolution of components in multicomponent mixtures. The problems are exacerbated when components form clusters, such as in the analysis of isomers. The determination of target analytes at trace levels also poses unique challenges. Selective detectors, in particular mass spectrometry (MS), can provide answers when merged components are capable of producing distinctive spectra. MS can compensate for poor chromatographic resolution in many cases but it cannot be applied for the deconvolution of isomers and closely related substances. In this situation, 2‐D GC is the only choice. Instrumentation in conventional 2‐D GC is based on one of two different effluent switching technologies. A valve can be used to divert the effluent from the primary column to a secondary column of different selectivity. In this arrangement, the sample inevitably comes into contact with the metal of the valve body. The other design is based on fluidic switching by application of a difference in pressure in the interface between the columns. This technology, generally referred to as Deans switching, can avoid metals in the sample flow path but it is technically more difficult than valve‐based technologies. Comprehensive 2‐D GC involves a focusing step. The effluent from the primary column is periodically injected into a high speed column in the form of narrow chemical pulses. The separation on the secondary column must be complete (or nearly complete) before the next pulse can be injected. The secondary column is polar, i.e. substances that have similar boiling points but differ in polarity can be resolved in the second dimension. The separations process is continuous and resembles data acquisition in routine gas chromatography/mass spectrometry (GC/MS). One of the true advantages of comprehensive 2‐D GC is that the separations mechanisms on both columns can be decoupled, leading to true orthogonality. Components with similar properties fall into clearly defined data spaces. The chromatograms show a measure of order which is useful in substance identification and group type analysis. Comprehensive 2‐D GC is still in its infancy. There is much room for improvements, including in the data acquisition/display area. Conventional 2‐D GC, however, is mature. Because of the complexity of 2‐D GC instrumentation, selective detection, i.e. GC/MS, is usually preferred where it is applicable. Many applications based on 2‐D GC have been published. The analysis of flavors/fragrances, petrochemicals and persistent organohalogens in the environment by 2‐D GC offers distinctive advantages over competing technologies.

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Temperature dependence of the resolution of diastereomeric isoprenoids in capillary GC. Experiments with 50 μm, 100 μm, and 250 μm i.d. Columns

Cited by 7 publications

References 16 publications

Determining the Extent of Biodegradation of Fuels Using the Diastereomers of Acyclic Isoprenoids

Determining the Extent of Biodegradation of Fuels Using the Diastereomers of Acyclic Isoprenoids

Two-Dimensional Gas Chromatography. Concepts, Instrumentation, and Applications - Part 1: Fundamentals, Conventional Two-Dimensional Gas Chromatography, Selected Applications

Multidimensional Gas Chromatography

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