Although science does not have a good grasp of these volatile compounds, nature cer­tainly does. Many animals identify each other by scent, locate their homes and other locations using odorant molecule tracers, and interact with plant species using odor-based chemical signaling. Gas chromatography (GC) is perfectly devised as an ana­lytical tool for analyzing these vapor-based trace compounds. In an interesting 2005 paper in Analytical Chemistry,* Dr. Alan Willse from the Pacific Northwest National Laboratory collaborated with researchers from the Monell Chemical Senses Center and the University of Pennsylvania to use gas chromatography-mass spectroscopy (GC-MS) to identify volatile compounds in the urine of mice and to use the results to identify the mice by population. Using two genetically distinct groups of mice, which differed only in genes of the major histocompatibility complex (MHC), the research­ers were successful in using the chemosignals to identify the differences in the phero­mones produced by the MHC genes of the two groups from among the thousands of compounds present in the samples. In another interesting example, researchers from the University of Vienna used GC to discover that the orchid Ophrys sphegodes releases pheromone compounds to, essentially, seduce pollinator bees to come to the flower.† The flower not only emits the same chemical compounds as the female bees but impressively emits them in the same proportions. The scientists used a nontra­ditional detector, “electroantennographic detection,” which relies on the male bees’ antennae as chemoreceptors. As a final example, Polish scientists used GC-MS to better understand the canine capacity for identifying cancer in human breath sam­ples.‡ As published in 2012, Buszewski and colleagues found positive correlations between GC-MS and dog indications for two trace volatile organic compounds im­plicated with the presence of lung cancer. Work such as this may lead to identifying biomarkers that have the potential for clinical use in monitoring human health.

* Willse A.; et al. Identification of Major Histocompatibility Complex-Regulated Body Odorants by Statistical Analysis of a Comparative Gas Chromatography/Mass Spectrometry Experiment, Anal. Chem. 2005, 77, 2348–2361.

Schiestl, F. P.; et al, Orchid Pollination by Sexual Swindle. Nature, 1999, 399, 421–422.

Buszewski, B.; et al. Identification of Volatile Lung Cancer Markers by Gas Chromatography– Mass Spectrometry: Comparison with Discrimination by Canines. Anal. Bioanal. Chem., 2012, 404, 141–146.