Inelastic electron tunneling spectroscopic study of biological compounds in human sweat adsorbed on alumina

Inelastic electron tunneling spectroscopy has been used for the detection and characterization of biological compounds in human sweat adsorbed on alumina surfaces. The sweat was collected from students and distributed to aqueous and benzene phases by solvent extraction. Both solutions were doped onto alumina surfaces of tunneling junctions, and the vibrational spectra of the adsorbed species were measured by inelastic electron tunneling spectroscopy. Analysis of these tunneling spectra showed that lactic acid in the sweat is extracted with water and selectively adsorbed on alumina. Adsorbed fatty acids were detected from the benzene phase. These biological compounds in the sweat solutions were found to react with the alumina to give about a monolayer of adsorbed carboxylate anions on the surfaces.