Gas Chromatography (GC)

This month's “GC Connections” continues the discussion of procedures for safe setup, use, and disposal of compressed gas cylinders in the chromatographic lab.

Many gas chromatographers are not fully aware of safe practices for handling high-pressure gas cylinders. GC operators should be trained to properly transport, install, connect, and maintain their gas supplies, as well to deal with emergencies. In the first of a two-part series, this month’s GC Connections examines the principal hazards and safety issues surrounding the compressed gas cylinder. Next month’s installment will present safe procedures for routine cylinder use.

While gas chromatographers may take their septa for granted, in fact these small and seemingly unremarkable polymer discs keep air out of the carrier gas stream when used in an inlet and keep sample intact and uncontaminated when used in a sample vial. Choosing the wrong septa can compromise method accuracy and repeatability as well as reduce column lifetime in extreme cases. This installment addresses septa for inlets and sample vials.

Chromatography connected with ion mobility spectrometry (IMS) is not commonly used, but is being investigated more. IMS is an independent analytical technique with very good detectability and a rather small separation ability. One favourable property of IMS is that it can work with ambient pressure and can be easily connected to a gas chromatograph. Analytical applications of GC–MS are very different and encompass investigations into food, medical science, environment, drugs of abuse, chemical warfare agents, and explosives.

Put yourself in their spot: How would you tackle analyzing a bag of gummy bears that showed up on your lab bench? Here, we offer some insights from the very capable finalists at The Conference on Small Molecule Science (CoSMoS), which was held in August 2015 in San Diego, California.

John Hinshaw presents his annual review of new developments in the field of gas chromatography seen at Pittcon and other venues in the past 12 months.

Incognito shares his thoughts on the importance of specifications for method transfer in gas chromatography (GC).

Jack Cochran’s new column “Practical GC” provides readers with practical advice and new experimental evidence for how to get the best results from their gas chromatography (GC) systems. This instalment looks at understanding and using split ratio for “shoot and dilute” GC.

Gas chromatography (GC) is an established and well-understood technique. As the cannabis industry grows, demand for analytical robustness is increasing for analytes such as pesticides, residual solvents, and terpenes. GC and GC coupled to mass spectrometry (GC–MS) are effective tools to address the demands of laboratories, growers, manufacturers, and consumers. This article provides an overview of the types of compounds that can be analyzed by GC, reviews the strengths and weaknesses of the analytical methods, and discusses areas of opportunity for chromatography.

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.

This study describes the need to recover compounds above the boiling point of naphthalene by optimizing the thermal desorption chemistry for the determination of VOCs from C3 to C26 in soil gas samples using Method TO-17. Figures of merit, such as breakthrough, precision, linearity and detection capability will be presented, in addition to evaluating its real-world capability at sites with moderate diesel and semi-volatile polynuclear aromatic hydrocarbon (up to pyrene) contamination, in the presence of high humidity.

Chromatographers often use the term carrier-gas flow and velocity interchangeably when discussing column parameters. In LC, the two terms scale together, but in GC they do not: Doubling the flow does not double the velocity. This month's “GC Connections” investigates the reasons for this non-intuitive behavior and how it affects best practices for gas chromatographers.

Jack Cochran’s new column “Practical GC” provides readers with practical advice and new experimental evidence for how to get the best results from their gas chromatography (GC) systems. The next instalment looks at GC inlet liner choice for “shoot and dilute” GC.

Thermal desorption sampling often provides a means for bringing otherwise intractable samples to a gas chromatography (GC) column for separation and detection. In this installment, John Hinshaw describes the principles of thermal desorption sampling in relationship to other analysis techniques for volatile solutes.

Jack Cochran’s new column “Practical GC” aims to provide readers with practical advice and new experimental evidence for how to get the best results from their gas chromatography (GC) systems. The first article in a series on split injection GC focuses on the advantages of using “shoot-and-dilute” GC.

The term “dead” volume often comes up in chromatography discussions and literature. This month, GC Connections addresses the nature of this phenomenon, when it can become a problem that affects chromatographic results, and how to understand and take control of it.

The Essentials: Optimizing Sample Introduction for Headspace GC

In GC split injection systems as much as 99% or more of the injected sample never enters the column: It is released downstream of the inlet where it can encounter and possibly perturb precision gas control devices. The split vent trap acts to prevent or at least moderate such effects. This month's installment addresses the operation and maintenance of split-vent traps..  

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.

Ionic liquids (ILs) have become recognized in gas chromatography (GC) as stable and highly polar stationary phases with a wide application range. Having customizable molecular structures, ILs also offer a particular tunability that provides additional selectivity, and therefore may improve separation for neighbouring analytes. This article presents specific properties of IL phase capillary GC columns, including polarity scale and inner surface morphologies of IL columns. Application of IL phases in achiral and chiral GC, and multidimensional GC, are highlighted.

As the flame ionization detector (FID) approaches its 60th anniversary in 2017, this installment examines the crucial role that it has played and continues to play for all types of gas chromatography. Without the FID, the early development of gas chromatography (GC) would have proceeded more slowly especially in the petroleum industry and related hydrocarbon application areas.

The author shares his insights into the principles and practice of implementing and improving upon the original method to quantitate cyanide at trace concentration levels in human blood matrices using automated cryogenic trapping isotope dilution static headspace gas chromatography–mass spectrometry (GC–MS).

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. 

Cigarette smoke is a highly complex matrix and presents analytical difficulties for the analyst performing compound identification by gas chromatography analysis coupled with mass spectrometric detection (GC–MS). The development of a novel trapping system and a modified GC–MS layout (using dual chromatographic columns and cryogenic focusing devices) has improved the chromatographic separation of volatile and semi-volatile compounds found in cigarette smoke. This improvement has led to the potential to identify compounds usually masked by the solvent peak. This approach has also reduced the amount of peak overlapping by increasing the chromatographic peak capacity with the use of two capillary columns chosen for their analytical specificity.

The main objective of this study was to evaluate the capabilities of gas chromatography (GC) with time-of-flight mass spectrometry (MS) for screening pesticides in fruits and vegetables using a purpose-built accurate-mass database.

Many of us use electron ionization (EI) in gas chromatography–mass spectrometry (GC–MS) without a good understanding of the technique and how we might manipulate the process to give more appropriate results or a better understanding of the analytes under investigation.

A guide to simple troubleshooting steps in gas chromatography (GC) with an emphasis on petrochemical analysis.

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.

The regulatory and practical issues that surround allergenic fragrance use within cosmetics and cleaning products are explored in this article.

The transit of peaks through a gas chromatography (GC) column depends strongly on the thermal profile they encounter on the way.