This presentation is about matrix-assisted laser desorption/ionization. It explains the sampling for TOF and its instrumentation.

1. MALDI-TOF
Mass
Spectrometry

2. Introduction
❖ MALDI is the abbreviation for "Matrix
Assisted Laser Desorption/Ionization.”
❖ MALDI is appropriate to analyze
biomolecules like peptides, lipids,
saccharides, or other organic
macromolecules.
❖ TOF stands for “Time of Flight”.
❖ This generates characteristic mass
spectral fingerprints which is compared
with large library of mass spectra.
❖ A versatile analytical technique to detect
and characterize mixtures of organic
molecules.

3. Principle of MALDI
❖ Matrix absorbs the ultraviolet light (nitrogen laser light, wavelength 337 nm) and converts it
to heat energy.
❖ The analyte is embedded on the Target Plate.
❖After a laser pulse, the irradiated spot is rapidly heated and becomes vibrationally excited.
❖Matrix molecules energetically ablated from the surface of the sample.
❖During ablation, the analyte molecules are usually ionized by being protonated or
deprotonated with the nearby matrix molecules.

5. Types of MALDI Variation Commonly
Used
❖ Laser: ultraviolet (UV) lasers are by far the most
important light sources.
❖ Time Of Flight: ideally suited to the MALDI ionization
process since the pulsed laser takes individual 'shots'
rather than working in continuous operation.
❖ Atmospheric Pressure: is an ionization technique (ion
source) that operates at normal atmospheric
environment.

6. TOF analyser
❖ The mass analyser used for MALDI is TOF analyser.
❖ It allows accurate mass determination for high molecular
weight species
❖ It makes TOF ideal for biomolecules.
❖ The ions desorbed by the laser pulse for accelerated in
an electric field to a kinetic energy of several KeV.

7. TOF Analyser
Accelaration
distance
Field Free Drift Distance
Electrode with gridSample
holder Detector

8. TOF Analyser
❖ Flight tube length and flight time
❖ At the end of the tube, ions hit the detector. And
is measured electronically.
❖ Lighter ions are accelerated more than the heavier ions
and reach the detector first.
2 m nanoseconds

9. TOF analyser
❖ Kinetic energy of the drifting ions is defined as
❖ 𝐸 𝑘𝑖𝑛 =
1
2
. 𝑚. 𝑣2
= 𝑧. 𝑒. 𝑉
❖ The velocity can be defined as
❖ 𝑣 =
𝐿
𝑡
❖ Substituting the velocity in eq.
❖
𝑚
𝑧
=
2.𝑒.𝑉
𝐿2 𝑡2

10. Sample pre-treatment
❖ Sample excess matrix.
co-crystallised
Inert
Stable in
vacuum
Embed with
analyte
Destruction
Fragmentation
Co-desorption of the analyte

11. sample treatment
• Dried droplet method
Mix Dry

12. Sample treatment
• Fast evaporation method

13. Apllications of Maldi
❖ Used for the analysis of proteins and peptides .
changes in structure can also be identified.
❖ Vey low amount of sample . sample preparation is
easy and spectra is simple.
❖ Very fast separation method

14. ❖ https://youtu.be/0jeFpXHZ8W0