On-line monitoring of UV-induced lipid peroxidation products from human skin in vivo using proton-transfer reaction mass spectrometry

Proton-transfer reaction mass spectrometry (PTR-MS) was used to study ultraviolet (UV) light-induced lipid peroxidation in human skin, in vivo. Emissions of volatile organic compounds (VOCs) in the mass range between 20 and 150 amu in the headspace of the skin of 16 healthy volunteers were monitored before, during and after irradiation in an on-line and non-invasive fashion. From these experiments, five volatile substances were found to reflect the damage caused by UV-radiation. The two major compounds (monitored at mass 45 and 59 amu) were identified as acetaldehyde and propanal using a combination of Tenax-based gas chromatographic pre-separation with PTR-MS. The other volatiles (with characteristic ions at, among others, masses 73 and 87 amu) could not be identified. Simultaneous measurement of the established lipid peroxidation biomarker ethene using laser-based photoacoustic trace gas detection revealed a similar pattern and statistically significant correlations between VOC production measured with PTR-MS and ethene. Variations in UV-radiation intensity were reflected by the amount of acetaldehyde and propanal emitted from the skin. Our results show that acetaldehyde and propanal can be used as biomarkers for lipid peroxidation.