David Barden

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.

This study describes the analysis of fragranced washing detergent and washing powder using probe-based headspace and immersive sorptive extraction, in conjunction with analysis by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS). As well as discussing the differences between the two samples, the analyte ranges covered by headspace and immersive sampling are compared.

This study describes the monitoring of potentially harmful volatile organic compounds (VOCs) emitted from respiratory medical devices, by pumped sampling and thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) analysis in accordance with ISO 18562 part 3. Emissions from two sets of face-mask supply tubing and three nasal cannulas were compared, and all were found to emit VOCs at levels that may give cause for concern.

This study describes the gas chromatography–mass spectrometry (GC–MS) analysis of trace-level “air toxics” in humidified cannister air, using cryogen-free preconcentration technology. We show that this method is able to detect 65 target compounds ranging from propene to naphthalene, with method detection limits as low as 0.7 pptv in SIM mode, making it compliant both with standard TO-15 methods, and with “trace TO-15” methods stipulating lower detection limits.

This proof-of-principle study shows that dynamic headspace sampling with thermal desorption–gas chromatography–time‑of-flight mass spectrometry (TD–GC–TOF-MS) analysis can be used to investigate the complex aroma profiles released from flavoured cookies. Key flavour compounds in chocolate-chip, peanut, and orange-cream cookies are highlighted, and the effect of raising the headspace extraction temperature is examined.

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.

This study shows that the organic compounds giving rise to the flavour of a variety of beverages can be identified by high-capacity sorptive extraction using PDMS probes, with analysis by thermal desorption–GC–MS.

The migration of chemicals through polymeric materials is difficult or impossible to model theoretically, placing an emphasis on experimental assessment to provide reliable empirical data. This article describes an investigation into the permeation of volatile chemicals through thin polymer membranes based on dynamic headspace, and how the information generated may be of value industrially - specifically in the fields of food packaging and personal protective equipment.

This study demonstrates that GC–TOF-MS can be a useful approach to generate comprehensive fragrance profiles of essential oils. Peak deconvolution enables discrimination between closely eluted compounds, and soft electron ionization, assisted by comparison of ion ratios, makes it possible to discriminate between isomeric monoterpenes with very similar mass spectra at conventional 70-eV ionization energies.

Carbon tetrachloride (CCl4) is a potent greenhouse gas in the troposphere, while in the stratosphere it contributes to ozone destruction. Global atmospheric models treat anthropogenic industrial processes as the sole source of atmospheric CCl4. However, some evidence suggests that biogenic sources may also contribute. This article describes grab-sampling with analysis by thermal desorption–gas chromatography–mass spectrometry (TD–GC–MS) to assess levels of CCl4 in a Central Amazonian rainforest. We find that ambient air mixing ratios within and above the forest, while agreeing with current equatorial estimates (120 ppt), show diurnal and canopy-height variations that suggest a biogenic source of CCl4, and therefore may be important for closing the gaps in the global atmospheric CCl4 budget.

This article describes the use of comprehensive two-dimensional gas chromatography (GC×GC) with time-of-flight mass spectrometry (TOF-MS) and tandem ionization for characterization and comparison of the composition of essential oils, aiding rigorous quality control.

This study describes a simple, quick approach for the sampling and analysis of nicotine, impurities, and flavour compounds in e-cigarette vapours. Combining thermal desorption (TD) with gas chromatography–mass spectrometry (GC–MS) analysis results in a versatile screening method for tackling the challenge of regulatory compliance and quality control in this rapidly expanding industry.

Demonstrating how the excellent sensitivity, stability and high-quality spectra produced by TOF MS can provide a rapid and robust solution for the quantitative analysis of environmental contaminants.

This article describes the use of a headspace thermal desorption–gas chromatography–time-of-flight mass spectrometry (headspace TD–GC–TOF-MS) method to analyze complex aroma profiles from hops, and highlights how it can provide a rapid yet robust approach when comparing similar samples. The article also examines the potential of “soft” electron ionization at 12 eV for distinguishing between structurally similar monoterpenoids and sesquiterpenoids to provide better characterization of the often subtle differences in headspace profiles between different hop varieties.

The inherent sensitivity and selectivity of time-of-flight mass spectrometry (TOF-MS) can be augmented by soft electron ionization (EI) to provide ultratrace-level quantitation of organotins in complex environmental extracts. These organotin species are a focus of current concern as environmental contaminants, but analysis using conventional 70 eV ionization energies is made difficult by their propensity to undergo extensive fragmentation. The use of soft EI helps to solve this problem by producing simplified spectra with enhanced diagnostic ions.

A method based on thermal desorption with gas chromatography–time-of-flight mass spectrometry (GC–TOF-MS) can elucidate how key volatiles vary with the size of the melon pieces. Such analytical information is of value in efforts to improve the quality and safety of ready-to-eat foods.

Rigorous conditioning of sorbent tubes is an essential part of any sampling and analysis protocol. This application note will explore the cost savings and productivity enhancements that can be made by off-line conditioning, rather than on‑line with the thermal desorber itself. In particular, we will focus on the revenue resulting from running more analytical samples, the cost-effectiveness of increasing sample capacity by this approach, and the benefits that stem from using nitrogen rather than helium.

Solid-phase microextraction (SPME) coupled with comprehensive two-dimensional gas chromatography and time-of-flight mass spectrometry (GC×GC–TOF-MS) can be used to detect trace-level fungicides and compounds responsible for undesirable attributes known as “organoleptic faults” in wine. Of particular interest is the analysis of trace-level fungicides, which are difficult to detect using conventional quadrupole GC–MS techniques without resorting to selected ion monitoring mode. 

This article describes sampling methodology for thermal desorption–gas chromatography (TD–GC) that can extend the compatible analyte range of tests used to determine chemicals released from materials, as well as associated indoor air quality measurements.

GC?GC–TOF-MS is used in forensic analysis for the analysis of tear gas lachrymators. In this article the analysis of a lachrymator standard is shown first, followed by the detection of capsaicin and dihydrocapsaicin at trace levels in a complex extract from contaminated clothing.

Despite the advantages of soft ionization ion-source technologies for improving confidence in the identification of a range of challenging analytes, soft ionization remains a niche technique for gas chromatography–mass spectrometry (GC–MS).

The detection and quantitation of allergens in complex cosmetics extracts using two-dimensional gas chromatography?time-of-flight mass spectrometry (GC?GC?TOF-MS) is described.

The detection and quantitation of allergens in complex cosmetics extracts using two-dimensional gas chromatography–time-of-flight mass spectrometry (GC×GC–TOF-MS) is described. In particular, variable-energy electron ionization is shown to enhance both the sensitivity and selectivity of analyses by generating mass spectra containing structurally significant fragment ions with an improved molecular ion signal.

This article shows how TD-GC-TOF-MS can be used to analyse the vapours released by strawberries.

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