Oral Presentation 28th Annual Lorne Proteomics Symposium 2023

Using Mass Spectrometry Imaging (MSI) to answer biological and environmental questions. (#31)

Brett Hamilton 1 , Welil Chan 1 , Karen L Cheney 1 , Robert Sullivan 1 , Matthias Floetenmeyer 1 , Mary J Garson 1 , Roger Wepf 1 , Phong Vo 1 , Trent Key 2 , Thi MinhHong Nguyen 1 , Phong Thai 1 , Kevin Thomas 1 , Jochen Mueller 1
  1. The University of Queensland, Brisbane, QUEENSLAND, Australia
  2. ExxonMobil Environmental and Property Solutions Company, Spring

Mass spectrometry imaging, pioneered by Caprioli and co-workers in the late 90s, has become a widely used technique which can reveal the spatial distribution of various analytes in a wide range of sample types. Arguably, MSI is at its most powerful when combined with other complementary analytical methodologies such as various forms of microscopy, LC-MS and NMR to name but a few. The first example to be discussed will involve examining the spatial distribution of latrunculin-A in the nudibranch, Chromodoris kuiteri. During this study we utilised a post ionisation laser, as described by Dreisewerd and co-workers, on an orthogonally accelerated time-of-flight (TOF) mass spectrometer to increase the sensitivity and enable the examination of 200 nm cryo-sections. During this study we apply methodologies developed for cryo electron microscopy tomography to sample preparation for MSI to improve the achievable spatial resolution. The second example involves a study looking at Perfluoroalkane sulfonic acids (PFSAs, a group of per- and polyfluorinated substances) including perfluorooctane sulfonate (PFOS) and perfluorohexanesulphonic acid (PFHxS) in concrete samples which have been exposed to these compounds at fire fighting training grounds. Concrete core samples were prepared for MSI analysis, which was carried out using desorption electrospray (DESI), on a multi-reflecting TOF mass spectrometer. DESI, fist described by Cooks and co-workers, is an ambient imaging technique and is more tolerant of topography changes in the sample than MALDI, allowing samples less regularly shaped and not perfectly flat, such as concretes, to be examined. DESI MSI was utilised to show the distribution of PFOS in 7 cm concrete core samples, revealing the extent of the penetration of PFOS. The DESI MSI results were compared to quantitative LC-MS of these same concrete samples. We show that DESI MSI was in good agreement with the LC-MS analyses. Taken together the DESI MSI and LC-MS represented an excellent approach to providing higher spatially resolved distribution maps and robust absolute LC-MS quantitation for PFOS in concrete core samples, revealing the extent of the distribution/penetration of PFOS.