Fig. 1. (a) Schematic of the LAP-MALDI source. (b) Close-up image of the LAP-MALDI sample irradiation, showing the ion transfer tube heated by a resistance wire opposite the sample plate with several liquid MALDI sample droplets. The irradiated sample droplet shows strong fluorescence. (c) LAP-MALDI MS spectrum (m/z 100–2000) obtained by acquiring data over one minute. (d) Workflow for the sample preparation and LAP-MALDI MS analysis of raw cow milk (TCA: trichloroacetic acid; ACN: acetonitrile; IPA: isopropanol; LSM: liquid support matrix). (e) Total ion chromatogram recorded for 50 separate milk samples analysed by LAP-MALDI MS.