Interfaces for on-line liquid sample delivery for matrix-assisted laser desorption ionisation mass spectrometry

Recent advances in on-line interfacing of liquid separation methods with matrix-assisted laser desorption ionisation (MALDI) mass spectrometry are reviewed. A number of concepts for this purpose are described, including pneumatic nebulisation creating an aerosol, use of continuous flow probes, and mechanical introduction with a rotating ball inlet or a vacuum deposition interface. Additionally, a MALDI source operating at ambient pressure has recently been introduced, opening a very simple and reliable way to obtain on-line MALDI measurements. Advantages and limitations of these interfaces are discussed.