Novel Applications and New Developments in Gas Chromatography

Exciting new uses for gas chromatography and its hyphenated forms show that there is an uncharted territory of applications and that there are limitations that still need to be overcome. The Tuesday afternoon oral session at Pittcon 2006, "GC-MS: Developments and Applications," gave the audience an idea of advances in GC and some new areas for the technique's application. John Chalmers of VS Consulting (Stokesley, United Kingdom) presided over the session.

Researchers at Tel Aviv University in Israel point out that GC-MS's limited capability with respect to analyzing thermally labile and low volatility large molecules are the technique's "Achilles Heel." Aviv Amirav, the lead author, presented a remedy in his talk "A New Type of GC-MS with Advanced Capabilities". Amirav and his colleagues from Tel Aviv University and Varian, Inc. have combined a supersonic molecular beam interface and its fly-through EI ion source with Varian's 1200 GCMS and MS-MS. The resulting high GC column flow rates bring the elution temperatures down by as much as 200 °C, which means larger molecules can be eluted and a larger range of labile compounds can be analyzed.

Gary Lavigne, from the University of Connecticut presented a solvent-free syringeless-injection method for the analysis of inorganic materials for trace compounds, which should rid of the "guesswork" and the cost and time overhead of solvents. He started the presentation with a novel animation showing how the new syringeless system works. Typically, GC involves using solvents to extract compounds from an inorganic substance. Doing that requires heating, ultrasonic agitation, filtering and volume reduction. It further requires injecting a prepared liquid sample into a heated injection port for GC-MS analysis. In the new device, made of a sample vial and a syringeless valve, the inorganic materials are introduced directly into a heated injection port of a GC for direct thermal desorption.

In one of the few organic tests of the technique that Lavigne presented, a preliminary result comparing of normal versus abnormally growing bone samples showed the presence of xylene in the abnormal tissue. Lavigne said that his group as well as the doctor they obtained the samples from could not explain the xylene. But they will be testing more patient samples to find out where it could be coming from.

A last minute change surprised some audience members. The final Pittcon program had listed a talk by U.S. Department of Agriculture researchers, who were going to present a comparison of several methods for the analysis of food flavors. But a talk by Philip Wylie of Agilent Technologies replaced the USDA presentation. Wylie described a new method for identifying indoor air pollutants using thermal desorption with gas chromatography and mass spectrometry. The technique uses retention time locking combined with deconvolution and RTL library searching.

In the second half of the session, Centers for Disease Control and Prevention researchers presented their research on the application of GC-MS in an important human health issue - monitoring the exposure of polycyclic aromatic hydrocarbons (PAH) in the general population, and identifying those at increased risk of exposure. PAHs have been linked to a number of human health adversities including cancer. The compounds are metabolized in the body to hydroxylated metabolites (HOPAH) and excreted in urine ad feces. The CDC researchers measured HOPAH in urine using enzymatic hydrolysis of these conjugates, liquid-liquid extraction on a Gilson 215 liquid handler and derivatization with silylating reagent. They followed this by gas chromatography (GC) in conjugation with high-resolution mass spectrometry (HRMS).

The last talk by Ohio University researcher Yao Lu touched on an interesting practical application for GC-MS: forensics. Specifically, the researchers touched on application in arson investigation. In 2003, there were 37,500 intentionally set structure fires that killed 305 people and caused almost $700 million in property loss, according to the U.S. Fire Administration. They talked about the importance of gas chromatography-differential mobility spectrometry in classifying petroleum-based accelerants, including gasoline, turpentine and paint thinner, in fire debris.

Other talks presented in this session were:

"Calibration of SPME for Quantitative Analysis by Gas Chromatography," by Gangfeng Ouyang at the University of Waterloo (Ontario, Canada).

"Coeluting Compounds in GC/MS? No Problem," by Rachel Kohn of Tovatech, LLC, (South Orange, New Jersey). "The Role of Evolved Gas Analysis (EGA) in Polymer Characterization," by R. R. Freeman of Quantum Analytics (Foster City, California).