DATA AVAILABILITY STATEMENT : The data that support the findings of this study are available from the corresponding author upon reasonable request.
SUPPORTING INFORMATION S1 : Experimental Section.
SUPPORTING INFORMATION S2 : FIGURE S1. Base peak ion (BPI) chromatogram of the selected analytes, L-carnitine (162.1192 m/z [M + H]+), caffeine (195.0907 m/z [M + H]+) and sulfadimethoxine (311.0930 m/z [M + H]+) using the BEH C18 column (top). Extracted ion chromatogram (EIC) for L-phenylalanine at 120.0883 m/z ([M-COOH]+) indicating the presence of the analyte when using the BEH C18 column (bottom). Compounds from a 1 ng/μl (5 μl injection) mixture were analysed using ESI + mode with UPLC-TOFMS. FIGURE S2. (A) PCA score plot showing no distinct clustering between the two skin regions sampled. (B) OPLS-DA score plot using ESI positive mode UPLC-IMS-HRMS data, over 16,000 markers, revealing separation between the ankle (red) and wrist (green) skin surface chemical profiles. (C) S-plot showing m/z, retention time (min) and drift time (ms) pairs of compounds contributing the differences in the chemical profiles of the ankle (red) and wrist (green) skin surface area. FIGURE S3. Base peak ion (BPI) chromatograms showing two skin regions sampled on Day 3. Three repeats per surface skin area sampled are shown. The top three traces are from the ankle skin surface area sampled and the lower three traces is from the wrist skin surface area sampled. TABLE S1: Compounds, tentatively identified during an untargeted analysis of the human skin surface, detected on the ankle and wrist skin surface area using a passive sampling method and solvent desorption with UPLC-IMS-HRMS. The compounds listed were classified, using chemometric techniques, as contributing to the difference between the ankle and wrist skin surface chemical profile. Mean, median and range are given in terms of detector counts.