What is the difference between AP-MALDI and vacuum MALDI?

AP-MALDI desorbs and ionizes under ambient pressure and introduces ions via ion optics into the analyzer, while vacuum MALDI is completed inside the vacuum chamber; the former is flexible, the latter has more controllable background and t-MALDI has better resolution.

Does AP-MALDI need vacuum introduction?

The sample as a whole need not enter the vacuum chamber; desorption occurs at ambient pressure, but ions must pass through transfer components into the analyzer's reduced-pressure region.

What is AP-MALDI's resolution?

Limited by laser spot and scan step, typically on the order of tens of microns, lower than transmission-mode MALDI's high resolution.

Is AP-MALDI suitable for matrix-free imaging?

It still relies on matrix spraying; if matrix-free is required, evaluate matrix-free ambient sources such as LDPI and DPI.

Technology Primer · Mass Spectrometry Imaging

AP-MALDI (Ambient MALDI)

AP-MALDI (Atmospheric Pressure MALDI) completes matrix-assisted laser desorption ionization in an ambient environment, retaining MALDI's high sensitivity for peptides, proteins, and lipids while removing the vacuum-introduction limitation, and is the ambient complementary path to vacuum MALDI (including transmission mode t-MALDI).

Table of Contents
Working Principle: Ambient Desorption and Ion Transfer Relationship with Vacuum MALDI / t-MALDI Imaging Performance and Suitability Comparison with Matrix-Free Sources

AP-MALDI (Ambient MALDI) — schematic diagram

Working Principle: Ambient Desorption and Ion Transfer

AP-MALDI irradiates the matrix-analyte co-crystal surface under ambient pressure with a pulsed laser; the matrix absorbs energy to trigger desorption and primary ionization, and the resulting ions are focused by ion optics in the ambient plume and introduced into the analyzer's reduced-pressure region. The key is ambient-to-vacuum transfer efficiency.

Compared with vacuum MALDI, the target is exposed to ambient pressure, making sample loading and exchange more flexible, and easier to couple with optical microscopy for morphology-molecule correlation.

Relationship with Vacuum MALDI / t-MALDI

All three share the matrix-assisted desorption basis: vacuum MALDI and t-MALDI are completed inside the vacuum chamber, with more controllable background, and t-MALDI leads in ion yield and resolution; AP-MALDI trades some background cost for ambient-operation convenience.

Selection should weigh resolution needs, sample throughput, and whether frequent sample exchange is needed: choose t-MALDI for high resolution, AP-MALDI for ambient flexibility.

Imaging Performance and Suitability

AP-MALDI can image peptides, proteins, and lipids on tissue sections; resolution is limited by laser spot and scan step, typically on the order of tens of microns; the ambient nature helps open-environment operation and in-vivo/large-sample work.

It still needs matrix-spray preparation; for heat-sensitive or easily oxidized molecules, operate under inert atmosphere to suppress background.

Comparison with Matrix-Free Sources

AP-MALDI still relies on matrix, with small-molecule matrix interference; for matrix-free, no-preparation, or ambient in-situ needs, compare with Neo-Source matrix-free ambient sources such as LDPI and DPI, choosing by analyte polarity and preparation acceptance.

Selection advice: choose AP-MALDI for large molecules, accepting matrix, needing ambient flexibility; choose LDPI/DPI for small molecules, matrix-free setups, or short-chain compounds.

Frequently Asked Questions (FAQ)

What is the difference between AP-MALDI and vacuum MALDI?: AP-MALDI desorbs and ionizes under ambient pressure and introduces ions via ion optics into the analyzer, while vacuum MALDI is completed inside the vacuum chamber; the former is flexible, the latter has more controllable background and t-MALDI has better resolution.
Does AP-MALDI need vacuum introduction?: The sample as a whole need not enter the vacuum chamber; desorption occurs at ambient pressure, but ions must pass through transfer components into the analyzer's reduced-pressure region.
What is AP-MALDI's resolution?: Limited by laser spot and scan step, typically on the order of tens of microns, lower than transmission-mode MALDI's high resolution.
Is AP-MALDI suitable for matrix-free imaging?: It still relies on matrix spraying; if matrix-free is required, evaluate matrix-free ambient sources such as LDPI and DPI.

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).

MALDI Transmission MALDI (t-MALDI)AP-SMALDI Atmospheric Pressure Matrix-Assisted Laser Desorption/Ionization Neo-Source MSI LDPI Laser Desorption Photoionization imaging ion source Vacuum MSI Ion Source

← Back to MSI Ion Source Knowledge Hub