Precursor Ion Selector Scan for Discovery of Analyte Specific Fragments in MALDI-TOF/TOF-MS/MS

摘要

Direct matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) measurements of chemically complex biological tissues has become an effective analytical approach. Tandem MS allows for the identification of detected signals. However, for in situ analysis, tandem MS is oftentimes not sufficient for unambiguous analyte identification. Inadequate precursor ion isolation causes complex mass spectra containing the fragment ions of multiple analytes. While the assignment of fragment ion identities can sometimes be made by matching fragmentation patterns to those found in databases, many compounds are not effectively identified using such an approach. To better much fragment ions to their parent ions we use an incremental shift in the precursor ion selector (PCIS) window across a mass range and compare changes in both precursor and fragment ion intensities and signal-to-noise ratios (S/N) to determine which are correlated to each other.