A new sampling method for human skin volatile analysis by comprehensive gas chromatography and mass spectrometry

Abstract

Volatile organic compounds (VOCs) emanating from the surfaces of human skin have been of great interest to researchers in medical and forensic fields, as well as to biologists studying the ecology of blood-feeding insect vectors of human disease. Applications of skin volatile analyses often require the relative abundances of analytes to be compared between samples in addition to the qualitative identification of the variety of compounds present. Current methodologies used for the non-targeted collection of a broad range of volatile analytes from the skin surface have limited quantitative capacity and there is a need to develop new methods for the collection and pre-concentration of skin volatiles which can facilitate such applications. The use of in-house developed passive sampling devices constructed in the forms of bracelets and anklets was investigated to address this need. The samplers were employed as non-invasive passive sampling devices for the non-targeted collection and concentration of volatile human skin emissions prior to comprehensive gas chromatographic time-of-flight mass spectrometric (GC × GC-ToFMS) analysis. The effects of experimental parameters, such as the orientation of the sampler relative to the skin surface and the duration of sampling, as well as data processing procedures, such as peak alignment and normalization, were investigated for their effect on the validity of the results obtained. Sampling of the compounds emanating from the skin surface of an individual has resulted in the tentative identification of hundreds of analytes based on mass spectra library matches and linear retention index (LRI) values. Compounds collected were from a wide range of compound classes some of which have not previously been reported as volatile skin emissions. Comparison of normalized unique mass peak areas between an individual’s ankles and wrists has revealed relative quantitative differences and similarities in the amounts of potential human semiochemicals affecting the behaviour of anthropophilic mosquito species. The results highlight the feasibility of the new sampling method for further expanding the current knowledge on human skin volatile emissions.