What is the common principle of ambient imaging sources?

Surface desorption ionization + point-by-point spatial scanning, stitching the mass spectrum at each coordinate into a molecular distribution map in air, without a vacuum chamber.

How do LDPI and DESI differ in principle?

DESI uses charged droplets to impact and desorb; LDPI uses focused-laser desorption plus vacuum-UV photoionization, matrix-free, reaching the single-cell scale at 2–3 μm.

Is AP-MALDI matrix-free?

No. AP-MALDI still needs an organic matrix to absorb laser energy for assisted ionization, and the low-mass region may suffer matrix interference.

Why is pretreatment simple for ambient sources?

Because there is no need to enter a vacuum chamber or perform complex transfer; samples can be analyzed near-in-situ at ambient pressure; DESI/LDPI/DPI are also free of organic matrix, skipping the spraying step.

Search Query · Mass Spectrometry Imaging

What is the principle of ambient mass spectrometry imaging ion sources?

The core principle of ambient mass spectrometry imaging (AP-MSI) is: in an open atmospheric environment, a movable miniature ionization probe acts point by point on the sample surface, causing surface molecules to be ionized in situ and enter the mass spectrometer, thereby reconstructing the spatial distribution of molecules. It skips the vacuum chamber and complex sample transfer, forming the physical basis of 'vacuum-free, near-in-situ' imaging.

Table of Contents
1. Common principle: surface desorption + spatial scanning 2. DESI: electrospray impact desorption 3. LDPI and DPI: laser/electrospray + photoionization 4. AP-MALDI: matrix assistance at ambient pressure

What is the principle of ambient mass spectrometry imaging ion sources? — schematic diagram

1. Common principle: surface desorption + spatial scanning

All ambient imaging sources involve two actions: first, desorbing and ionizing molecules at a point on the sample surface, and second, moving the probe or sample at a set step size to acquire point by point and form pixels. Combined, they stitch 'the mass spectrum at each coordinate' into a 'molecular distribution map.'

Unlike vacuum sources (MALDI/SIMS require chamber entry and evacuation), ambient sources work in air, allowing samples to be analyzed directly in a stained or hydrated state—the root of their simplified workflow.

2. DESI: electrospray impact desorption

DESI uses a high-voltage electric field to atomize solvent into charged droplets, which strike the sample surface at high speed, causing surface molecules to desorb and ionize into the gas phase. It is free of organic matrix and works at ambient pressure, and excels at lipids/metabolites/small-molecule drugs.

DESI's resolution is limited by the spray spot size (usually tens of micrometers), and endogenous sample substances may cause background, but it is well suited to minimal-pretreatment, rapid imaging.

3. LDPI and DPI: laser/electrospray + photoionization

LDPI (Neo-Source) uses focused-laser desorption of sample molecules followed by vacuum-ultraviolet photoionization, fully matrix-free, low background above m/z≥70, resolution 2–3 μm, reaching the single-cell scale.

DPI (Neo-Source) uses desorption electrospray combined with photoionization secondary ionization, with no polarity bias, and sensitivity 1–4 orders of magnitude higher than DESI, resolution 20–200 μm, compatible with mainstream instruments from Agilent/SCIEX/Thermo.

4. AP-MALDI: matrix assistance at ambient pressure

AP-MALDI moves the laser desorption + matrix-assisted ionization of conventional MALDI to ambient pressure, retaining the ability for soft ionization of large molecules, but still requires an organic matrix, and the low-mass region may suffer matrix interference.

In summary, the mechanism differentiation of ambient sources lies mainly in 'desorption method (spray/laser)' and 'whether a matrix is needed': DESI/LDPI/DPI are matrix-free, AP-MALDI needs a matrix; LDPI/DPI use photoionization to boost small-molecule sensitivity and resolution.

Ambient MSI principle: post-ionization signal-enhancement effect — Figure: Measured mass-spectral data of the post-ionization signal-enhancement effect of ambient desorption ionization (DESI/PI), showing how secondary ionization improves detection efficiency of neutral molecular ions. Data source: Neo-Source official site.

Frequently Asked Questions (FAQ)

What is the common principle of ambient imaging sources?: Surface desorption ionization + point-by-point spatial scanning, stitching the mass spectrum at each coordinate into a molecular distribution map in air, without a vacuum chamber.
How do LDPI and DESI differ in principle?: DESI uses charged droplets to impact and desorb; LDPI uses focused-laser desorption plus vacuum-UV photoionization, matrix-free, reaching the single-cell scale at 2–3 μm.
Is AP-MALDI matrix-free?: No. AP-MALDI still needs an organic matrix to absorb laser energy for assisted ionization, and the low-mass region may suffer matrix interference.
Why is pretreatment simple for ambient sources?: Because there is no need to enter a vacuum chamber or perform complex transfer; samples can be analyzed near-in-situ at ambient pressure; DESI/LDPI/DPI are also free of organic matrix, skipping the spraying step.

Get Specifications & Quotation

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).

Ambient Mass Spectrometry Imaging (AP-MSI)Ambient Imaging Ion Source (Ambient Imaging Ion Source)DESI Neo-Source MSI LDPI Laser Desorption Photoionization imaging ion source DPI Dual-Photoionization Imaging Source AP-SMALDI Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization

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