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In 2001, Japanese researchers reported that after the age of 40, some individuals develop a malodor known as “aging odor,” attributed to the presence of unsaturated C9, 2-nonenal. George Preti, PhD, a member of Monell Chemical Senses Center and an adjunct professor of dermatology at the University of Pennsylvania School of Medicine, was interested by this report and began to conduct research of his own. His work1 analyzed the volatile organic compounds (VOCs) emitted from human skin; however, instead of sampling VOCs from the axillae (underarms) considered the primary source of human body odor, his team sampled from non-axillary skin, including the upper back and forearms, that also emits volatile metabolites.
Sampling VOCs from Skin
For Preti’s study, 25 participants, 13 male and 12 female, showered and bathed with a provided, fragrance-free liquid soap/shampoo for 7–10 days prior to being tested. “We wanted to lessen the influence of exogenous sources of VOCs from consumer products,” said Preti, who added that test subjects were also asked not to use fragrance or deodorant during this time.
Before sampling the VOC content, researchers had the test subjects climb stairs or run on a treadmill to generate sweat. According to Preti, a funnel approximately 10 in. in diameter for the back, and 6 in. for the forearm, was then placed over the skin.
“The funnel is used to concentrate the space air tested into a smaller area,” said Preti. A solid phase microextraction (SPME) fiber was then placed in the funnel, close to the skin, for 30 min. and this was repeated on the opposite side of the back and the forearm. Samples were then inserted into a GC/MS apparatus hot injector for 1 min to emit the VOCs collected in the fiber. The air VOC content also was tested with a SPME fiber to rule out VOCs in the surrounding air.
“Heavier materials are not likely to come off the skin in the vapor phase,” said Preti. Therefore, the researchers collected a solvent extraction of skin secretions.