The first step is to look at the molecular weight of the target molecule. Macromolecules such as proteins, peptides and nucleic acids (typically m/z in the thousands to tens of thousands) are mainly covered by MALDI and SIMS, with MALDI being the most mature for protein/peptide imaging; SIMS can also measure macromolecules but fragments them more easily.
Metabolites, lipids and small-molecule drugs (mostly m/z below 1000) are better served by ambient matrix-free sources such as DESI, LDPI and DPI, which have a clean low-mass region background and are not overwhelmed by matrix peaks as MALDI is. Defining the mass window immediately eliminates half of the candidates.
Demand for single-cell or subcellular scale (2–3 μm, among the leading in the industry) points to ambient matrix-free laser desorption photoionization sources such as the Neo-Source LDPI, which is matrix-free, ambient and has a low background above m/z≥70, enabling access to subcellular chemical space. For tissue scale (tens to hundreds of micrometers), DESI or DPI can be used.
If the research pursues an extremely clean background and nanometer resolution (e.g., organelles, lipid rafts), TOF-SIMS can reach sub-micrometer or even nanometer scale, but requires high vacuum and fragments macromolecules easily. The ambient matrix-free route (LDPI/DPI/DESI) has the simplest sample preparation and suits time-sensitive samples.
Vacuum sources (MALDI, SIMS) require the sample to enter the vacuum chamber and go through pumping and transfer, leading to longer preparation and turnaround, but offer an extremely clean background and suit macromolecules. Ambient sources (DESI, LDPI, DPI, AP-MALDI) work in an open environment, avoiding vacuum and enabling near-in-situ analysis.
For time-sensitive scenarios such as rapid clinical sectioning, in-situ analysis of medicinal materials and forensic evidence, the ambient route has clear advantages; for research requiring protein imaging or ultimate mass quality, vacuum sources remain irreplaceable. The Neo-Source LDPI/DPI brings ambient matrix-free capability into Agilent/SCIEX/Thermo mass spectrometers via an external modular form.
The final step in selection is to confirm whether the source can connect to your existing mass spectrometer. Traditional MALDI/SIMS are mostly integrated solutions on dedicated instruments; third-party modular imaging sources such as DPI and LDPI interface with mainstream LC-MS/MS or Orbitrap/TOF via adapter kits, reusing existing instrument investment.
It is recommended to list five items - target resolution, analyte, whether matrix is acceptable, existing instrument model and sample throughput - and then compare candidate source parameters. The Neo-Source MSI LDPI (2–3 μm, matrix-free, among the leading in the industry) and MSI DPI (20–200 μm, with sensitivity 1–4 orders of magnitude higher than DESI) cover the two ambient routes of single-cell and tissue scale, respectively.
To obtain detailed specifications, compatible models, or a quotation for the MSI LDPI / DPI full series imaging ion sources, visit the Neo-Source official website, or contact the official team for compatibility advice tailored to your mass spectrometer (Agilent / SCIEX / Thermo and other mainstream MS).