Simplifying GC

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Connections, columns, chemistries and more make gas chromatography easier to use and more robust

Scientists started separating samples with gas chromatography (GC) in the early 1950s, and the technology is continually becoming easier to use. “I think GC is pretty simple,” says Alan Friedman, associate professor of materials, design and innovation (engineering) and a member of the University at Buffalo’s (N.Y.) shared instrument laboratory. Knowing the basics takes a scientist a long way in using GC. The most complicated part from the human side, says Ning Dai, assistant professor of civil, structural and environmental engineering at the University at Buffalo, is a “basic understanding of chromatography.” To make GC easier to use or more efficient, advances in instrumentation help. Dai says an autosampler is the most recent simplification of using GC that she likes most.

One of the most fundamental parts of a GC is the inlet—where the sample is injected. Still, Tim Anderson, product manager at Phenomenex (Torrance, Calif.), calls the GC inlet one of the most complicated parts of this technology. “The ideal GC column  can be selected [and] the sample appropriately prepared; however, all of this can be lost by mismanaging inlet parameters,” Anderson says. The inlet impacts various features of chromatography, including the resolution and the shape of the peak.

Scientists from the Universidad Nacional de Colombia (Bogotá) used GC plus mass spectrometry to analyze exotic fruits for pesticides.¹ They wrote: “The most relevant parameters of a multimode inlet were optimized to increase the injection volume up to 25 μL using solvent vent mode in order to improve the sensitivity of the gas chromatography-mass spectrometry system.” The samples consisted of complicated extracts, and measuring small quantities of pesticides required a fine-tuned system—especially getting the GC inlet right.

Installing the column can also create a challenge. “The column needs to be properly trimmed and inserted to the appropriate depth, both of which can easily be done incorrectly, affecting the chromatography,” Anderson explains. “As I like to tell users, one can be the smartest Nobel Laureate in chemistry, but at the end of the day the physical installation of the column can still be a challenge for most people.” The inlet must be optimized and the column inserted properly or the results and throughput will suffer.

Software adds to the ease of using GC. National Institute of Standards (NIST) software searches, says Friedman, made it easier than ever to analyze GC data. Other developments in software also make GC simpler to use. The “software-assisted development of the large-volume injection method” is one of Dai’s favorite simplifications.

Uncomplicating the connections

 Some platforms, such as the Agilent Intuvo 9000 GC system, incorporate a variety of features that reduce the need for expertise in running samples. (Image courtesy of Agilent.)

The components of a GC must be put together correctly to get the best results, and the easier that is, the more people will use it with good outcomes. “Probably the most complicated aspect of GC is making connections correctly,” says Eric Denoyer, director of marketing, GC and workflow automation at Agilent (Santa Clara, Calif.). “Assuring that the nut and ferrule are tightened to just the right level—and not overtightened—is a skill that must be developed.”

Agilent’s Intuvo technology eliminates nuts and ferrules. “Intuvo’s direct connection technology allows a user to make a connection with a simple click of a torque driver, eliminating any uncertainty [as to] whether the connection was made correctly or not,” Denoyer explains. “Moreover, Intuvo incorporates automatic leak detection to assure and confirm that the connection was made properly.” Intuvo’s disposable Guard Chip keeps unwanted material out of the column, so it doesn’t need to be trimmed.

This combination of technological advances makes GC available to more users. “We expect that, at the very least, this will make GC more accessible as a simpler tool, especially to the research community,” Denoyer says. “Researchers tend not to be GC experts, but often would like to use GC as a confirmation tool.” This technology can even create a self-serve system in the lab, where almost any researcher can analyze a sample with GC.

Creating new column chemistry

 Specialized items help scientists set up gas chromatography systems with less chance of errors. (Image courtesy of Phenomenex.)

Tools developed for specific applications also make GC easier to use. “The new Phenomenex Zebron ZB-FAME column was recently developed for the fast analysis of fatty acid methyl esters,” says Anderson. “Fatty-acid analysis has been more of an interest due to regulatory changes as well as marketplace changes with food manufacturers.”

A team of researchers from the Indiana University School of Medicine in Indianapolis used Phenomenex Zebron ZB-WAX GC columns to measure the fatty-acid composition in emulsions of lipids.² They concluded: “Our data suggest that the improved method can be easily used to accurately determine fatty acids (C6–C24) in functional foods and lipid emulsions.”

Today’s drivers in the food industry make such techniques even more crucial. If a product advertises, say, zero trans fats, a manufacturer needs an efficient method that ensures that. “The current method uses longer, and more expensive, GC columns,” Anderson explains. “The Zebron column achieves better results in less time.”

Step-by-step workflows in GC do not change much—if at all. It’s column chemistry that makes different applications possible. As Anderson says, “Scientists can do more interesting work with advances in column technologies.” Scientists can also do more as manufacturers give GC more horsepower in easier-to-use technology.

References

1. España Amórtegui, J.C.; Guerrero Dallos, J.A. Practical aspects in gas chromatography-mass spectrometry for the analysis of pesticide residues in exotic fruits. Food Chem. 2015; doi:10.1016/ j.foodchem.2015.02.113.
2. Xu, Z.; Harvey, K. et al. An improved method for determining medium- and long-chain FAMEs using gas chromatography. Lipids 2010; doi: 10.1007/s11745-009-3382-7.

Mike May is a freelance writer and editor living in Florida. He can be reached at [email protected].