Figure 1.

On-tissue spotting experiments by MALDI and DESI MSI platforms using Amplifex as a derivatization reagent. (a) Vitamin D–Amplifex derivatization reaction scheme and (b) on-tissue spotting experiments. (I) Optical image of control tissue section (II) MALDI–MSI molecular distribution map of spotted d₆-25-(OH)-D₃ Amplifex derivative at m/z 738.5435 ± 0.005. (III) DESI–MSI molecular distribution map of spotted ISTD vitamin D standard Amplifex derivative at m/z 738.5435 ± 0.005; (c) representative zoomed-out single-pixel mass spectrum of d₆-25-(OH)-D₃-Amplifex derivative spotted region using (I) DESI-qTOF-MS. (II) MALDI–FTICR–MS both with a mass accuracy of 1.08 ppm against theoretical monoisotopic mass. Data were normalized to TIC. Spatial resolution was set at 100 μm, with scale bars shown. Signal intensity is depicted by color on the scale shown. Spectrum was postcalibrated to CHCA cluster matrix ion at +ve m/z 417.0483.