Multidimensional GC

New approaches to sample preparation are being developed for microbial metabolomics to address the inherent complexity of this type of analysis.

The benefits that GC×GC–TOF-MS with tandem ionization and chemometrics offer for fragrance profiling and authenticity evaluation.

This month we interview Katelynn Perrault, Associate Professor of Forensic Sciences and Chemistry at Chaminade University of Honolulu in Honolulu, Hawaii, about her work translating 1D GC methods to effective comprehensive 2D GC (GC×GC) methods for forensic applications and the benefits that GC×GC offers the analyst.

LCGC Europe spoke to Yada Nolvachai about a new approach that offers “super-resolution” for comprehensive two‑dimensional gas chromatography (GC×GC) methods.

In the present research, similar chromatography fingerprints were obtained using finely-tuned cryogenic-modulation (CM) and flow-modulation (FM) comprehensive two-dimensional gas chromatography–mass spectrometry (GC×GC–MS) experimental conditions.

In gas chromatography, heating the sample in the inlet can lead to sample losses and loss of quantitative reproducibility, but these problems can be avoided using cold sample introduction. This article describes various types of cold injection and how they can benefit the analyst.

This critical review describes recent applications and instrumental trends in comprehensive two-dimensional gas chromatography (GC×GC), with particular (though not exclusive) attention to the period 2018–2019 and that the concept of GC×GC is inherently simple. The maturity of GC×GC and future developments are also discussed.

In this instalment of “GC Connections”, the advantages of multidimensional chromatography with HPLC as the first dimension and GC as the second are discussed.

GC–MS is considered the gold standard in forensic trace evidence analysis because of its ability to chromatographically separate and analyze components in mixtures. Although GC×GC–MS has been used extensively in the oil and petroleum and flavour and fragrance industries, it has not been fully explored in the forensic sector. However, forensic scientists often encounter highly complex samples that would benefit from the capabilities of GC×GC–MS, such as, sexual lubricants, automobile paints, and tyres. GC×GC–MS analysis can allow for the deconvolution of coeluted components while providing increased sensitivity of minor components to help benefit any forensic laboratory.

LCGC Europe spoke to Guilherme L. Alexandrino from the University of Copenhagen, Denmark, about the benefits of combining a modern “pixel-based” chemometrics technique with comprehensive two‑dimensional gas chromatography (GC×GC) in petroleomics applications.

This proof-of-principle study shows that polymer-based sorptive extraction probes, coupled with secondary focusing by thermal desorption and analysis by flow-modulated GC×GC–TOF-MS/FID, can be used to separate and identify flavour compounds in milk. As well as comparing the profiles of dairy and non-dairy milks, this article highlights the practical benefits of this sampling procedure, the ability of two-dimensional GC to physically separate components that would coelute in one-dimensional GC, and the use of software tools to improve workflow.

Multidimensional chromatography, or comprehensive chromatography, is a well-established technique for the analysis of complex mixtures. However, the technique is often perceived as highly complex and difficult to put into practice for routine applications. Nonetheless, the technique provides exceptional potential for addressing challenging separations. The addition of a dilution factor allows multidimensional chromatography to provide a high level of flexibility and selectivity. The dilution effect is achieved by using a column chemistry format compatible with large flow rates, which now offers the option of large volume injection without volume or mass overload issues. This novel solution can reduce or eliminate the need to add a solvent exchange step, such as evaporation or reconstitution, which significantly reduces the most time-consuming part of the sample preparation process.

The concept of (heart-cutting) multidimensional gas chromatography (MDGC) was introduced shortly after the invention of gas chromatography (GC). In that first experiment, the term “two-stage” was used to define the multidimensional process in applications involving the heart‑cutting of four hydrocarbon fractions, ranging from C5 to C8. The latter were separated first on a nonpolar packed column, and then on a polar one. A rather complex combination of valves enabled two-dimensional (2D) analysis. The great potential of the approach became immediately evident.

This article provides a short overview of the theory and practice of the rapidly developing field of two‑dimensional gas chromatography (GC×GC). Included in the discussion are a summary of the detectors used, an assessment of the options available for modulating the first-column eluate, and some recent developments in methodologies for interpreting the results.

The enhanced separation power of two-dimensional (2D) chromatography has become accessible thanks to the commercialization of dedicated two-dimensional systems. However, with great separation power comes great system complexity. All two-dimensional systems require a means for collecting and transferring fractions of the first dimension to the second dimension typically via a loop-based interface in on-line methods. It is important to collect a sufficient number of fractions to prevent loss of the first dimension resolution; that is, the sampling rate must be sufficient to prevent undersampling. Another key parameter to consider is selectivity. By coupling two selectivities that have unrelated retention mechanisms we are able to exploit the different physiochemical characteristics of the sample we wish to separate. This is the concept behind the term orthogonality. By coupling orthogonal selectivities and reducing under‑sampling, our system should be able to achieve the theoretical maximum two-dimensional peak

Deans switch two dimensional gas chromatography is a powerful tool for identification and quantitation of trace components in a complex matrix. With this setup, operators no longer work in the dark. MDGCsolution software makes the heart-cut easy and straightforward.

In this article comprehensive GCxGC–qMS is shown to be a suitable tool for targeted and untargeted analysis in the flavours and fragrances industry.

GCxGC started out as a specialized technique. However, the technique and it's instrumentation have evolved significantly in the past decade. Does it make sense to use GCxGC in routine analysis?

Latest newsletter from June 12 2014.

Newsletter from June 5 2014.

The latest newsletter from March 20.

Frank L. Dorman of Penn State University talks about the evolution of GCxGC and the key advantages and disadvantages of the technique, including why fear of its complexity gets in the way of its broader use.

The latest newsletter from March 13.

Click here to view the full European E-newsletter from March13 2014.

Here, a method to characterize edible oils and edible oil mixtures through fingerprinting and the isolation of individual analyte differences is reported. Aroma and flavor analytes in extra virgin olive, olive, peanut, grapeseed, and vegetable oils were sampled with headspace solid-phase microextraction (HS-SPME).

Pulsed-flow-modulated comprehensive two-dimensional gas chromatography with flame ionisation detection was used to separate and identify all common sulphur compounds found in natural gas.

LECO Corporation

A method able to quantitate odorants at levels as low as 100 ppb (v/v)

A carefully chosen analytical technique can enhance the inherent advantages of passive sampling of watercourses over more traditional "grab" or "spot" sampling.