2.3. MS and MSI analysis
MSI experiments were performed on a MALDI-TOF/RTOF instrument (UltrafleXtreme,BrukerDaltonics,Germany) in positive linear or reflectron mode, equipped with a 355nm SmartBeam laser pulsed at 2000Hz and ona MALDI-TOF/RTOF instrument (AXIMATOF2, ShimadzuKratos Analytical,UK)equipped with a 20Hz nitrogen (337nm) laser. At a spatial resolution of 100–150 µm, mass spectra based on 1000 (AXIMATOF2) or 2000 (UltrafleXtreme) single laser shots were acquired per position over an average sample size of 8000 single imaging positions for polymer samples (approx. 8×8mm) if not otherwise stated.For image reconstruction FlexImaging v.3.0 software (BrukerDaltonics)and Biomap 38.04 (Novartis,Switzerland)wasused.