Voyager DP-263-S Betriebsanweisung PDF herunterladen (Seite 38)

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Chapter 1 Introducing the Voyager™ Biospectrometry™ Workstations

1-8 PerSeptive Biosystems

Matrix-Assisted

Laser Desorption

Ionization (MALDI)

In Matrix-Assisted Laser Desorption Ionization (MALDI),

sample is embedded in a low molecular weight,

UV-absorbing matrix that enhances sample ionization.

The role of the matrix is to facilitate intact desorption and

ionization of the sample.

The matrix is present in vast excess of sample, and

therefore isolates individual sample molecules.

Figure 1-4 illustrates the ionization of sample.

Figure 1-4 Matrix-Assisted Laser Desorption

Ionization

Time-of-Flight

(TOF)

Time-of-flight mass spectrometry works on the principle that if

ions are accelerated with the same potential from a fixed point

and at a fixed initial time and are allowed to drift, the ions will

separate according to their mass-to-charge ratios. Lighter ions

drift more quickly to the detector. Heavier ions drift more

slowly (Figure 1-5).

Ions generated by MALDI exhibit a broad energy spread after

acceleration in a stationary electric field. By forming ions in a

field-free region, and then applying a high voltage pulse after a

predetermined time delay to accelerate the ions, this energy

spread can be minimized. See Section 1.4, Voyager-DE™

(Delayed Extraction™) Technology, for more information.

Matrix

Sample

Laser

Energy transfer

Ionization

from matrix to

sample

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