What are the ambient ionization sources?

DESI, AFADESI, LDPI, DPI, AP-MALDI, DART, APCI, APPI and others, with mechanisms spanning droplet impact, laser desorption, photoionization and gas discharge.

Which can do imaging?

Those with point-by-point scanning: DESI/AFADESI, LDPI, DPI, AP-MALDI; DART requires a moving platform to scan and has weaker uniformity than dedicated imaging sources.

What is the difference between DART and DESI?

DART ionizes surface molecules using excited gas and has no scanning mechanism; DESI uses charged droplets impacting the surface to desorb and is naturally scannable for imaging.

Does LDPI belong to ambient ionization?

Yes. LDPI works in an open ambient environment via laser desorption plus vacuum ultraviolet photoionization, and is a matrix-free 2–3 μm (among the leading in the industry) ambient imaging source.

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What types of ambient ionization sources are there?

Ambient ionization refers to a class of soft ionization techniques in which the sample is directly ionized in the open atmosphere without pre-separation or vacuum. Representative examples include DESI, DART, APCI, APPI and Neo-Source LDPI. Among them, those with point-by-point scanning capability constitute ambient imaging ion sources, while the rest mostly serve direct-injection rapid analysis.

Table of Contents
1. Classification by desorption method 2. Which have imaging capability 3. Applicable forms and scenarios 4. Selection essentials

What types of ambient ionization sources are there? — schematic diagram

1. Classification by desorption method

Impact desorption: DESI uses charged droplets impacting the surface to desorb; AFADESI is its air-assisted improved variant. Laser desorption: LDPI uses laser desorption plus photoionization, matrix-free, 2–3 μm (among the leading in the industry). Electrospray plus photoionization: DPI uses desorption electrospray combined with photoionization secondary ionization.

Gas discharge or plasma: DART uses inert gas passing through dielectric barrier discharge to generate excited species that ionize surface molecules; APCI/APPI mostly use corona discharge or vacuum ultraviolet light to ionize LC effluents and have no spatially resolved mechanism themselves.

2. Which have imaging capability

Only those with a point-by-point scanning mechanism are used for imaging: DESI/AFADESI, LDPI and DPI are typical imaging ambient sources; AP-MALDI, which brings MALDI to ambient pressure, also counts as an imaging source.

DART itself has no scanning mechanism and requires a moving platform to perform 2D scanning; its resolution and uniformity are weaker than dedicated imaging sources, leaning more toward rapid surface screening than fine imaging.

3. Applicable forms and scenarios

DESI/LDPI/DPI suit spatially resolved analysis of tissue, herbal medicine and material surfaces; DART suits rapid direct analysis of solid surfaces such as packaging, documents and fingerprints; APCI/APPI suit LC-MS effluent (non-imaging) quantification.

Understanding this distinction avoids conceptual mix-ups: ambient ionization is the broader family, while ambient imaging ion sources are the subset of it that has spatial resolution. Neo-Source LDPI/DPI bring matrix-free ambient ionization into mainstream mass spectrometry imaging.

4. Selection essentials

If spatial distribution is needed, choose DESI/LDPI/DPI/AP-MALDI; if rapid surface screening is needed, choose DART; if LC effluent ionization is needed, choose APCI/APPI. Molecule type also constrains the choice (mid-to-low polarity small molecules lean toward APCI/APPI, metabolites or lipids lean toward DESI/LDPI).

For small molecules, matrix-free, single-cell or subcellular needs, LDPI (2–3 μm (among the leading in the industry), low background above m/z≥70) is currently one of the routes with the highest spatial resolution among ambient ionization sources.

Frequently Asked Questions (FAQ)

What are the ambient ionization sources?: DESI, AFADESI, LDPI, DPI, AP-MALDI, DART, APCI, APPI and others, with mechanisms spanning droplet impact, laser desorption, photoionization and gas discharge.
Which can do imaging?: Those with point-by-point scanning: DESI/AFADESI, LDPI, DPI, AP-MALDI; DART requires a moving platform to scan and has weaker uniformity than dedicated imaging sources.
What is the difference between DART and DESI?: DART ionizes surface molecules using excited gas and has no scanning mechanism; DESI uses charged droplets impacting the surface to desorb and is naturally scannable for imaging.
Does LDPI belong to ambient ionization?: Yes. LDPI works in an open ambient environment via laser desorption plus vacuum ultraviolet photoionization, and is a matrix-free 2–3 μm (among the leading in the industry) ambient imaging source.

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 Ionization Technology (Ambient Ionization)DESI DART Direct Analysis in Real Time Ionization APCI Atmospheric Pressure Chemical Ionization Ambient Mass Spectrometry Imaging (AP-MSI)Neo-Source MSI LDPI Laser Desorption Photoionization imaging ion source DPI Dual-Photoionization Imaging Source

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