Page 8 - Shimadzu-MassSpectrometerCatalog

Mass spectrometers must first ionize sample molecules.

Many type of ionization have been developed.
Electron ionization (EI) ionizes samples using accelerated thermal electrons,
70 eV. EI is generally used for samples, whose molecular weight is less than
High Polarity
1000. It is typically used in combination with a gas chromatograph to ana- LCMS
lyze highly volatile molecules or gases.
Electrospray ionization (ESI) ionizes samples in solution by spraying them. It Middle Polarity
is mainly used in combination with liquid chromatographs.
GCMSS MALDI
Matrix Assisted Laser Desorption/Ionization (MALDI) desorbs sample mole-
Low Polarity
cules by laser energy and ionizes those by transferring charge from matrix
100 1000 5000 10000 100000
ions. MALDI can apply wide range of samples by changing matrix reagents,
Molecular Weight
hence, this ionization method apply to synthetic polymer and complicated
samples.

ESI (Electrospray Ionization) ESI From column

ESI probe
A sample solution is introduced to capillary applying high electric
(1) Capillary
voltage and sprayed at the edge of capillary. Droplets of sample
solutions are charged and sample molecules are ionized in liquid (2) (2) Nebulizer gas
phase. (1) (3) Dry gas
ESI is best suited to ionizing medium-to-high polarity substances,
(4) DL (desolvation line)
peptides, proteins, and oligonucleotides.
(3) (4)

DUIS (ESI+APCI) DUIS From column

ESI probe
The DUIS-2020 is a dual ion source that ionizes samples using both
(1) Nebulizer gas
ESI and APCI (atmospheric pressure chemical ionization) modes.
This is best suited to ionizing low-to-medium polarity substances. (1) (2) Corona needle
(3) Dry gas
(4) DL (desolvation line)
(2) (3) (4)

MALDI : Sample molecules
: Matrix
(Matrix Assisted Laser : Positive ions
: Negative Ions
Desorption/Ionization)
Laser
After applying the sample and matrices solution on a sample target Vacuum
and dry up, laser irradiates to sample spot. The sample and matrix
molecules are desorbed and ionized, rapidly.
Sample
MALDI enables to ionize high molecular weight compounds, such
Sample target Sample target
as proteins and polymers without dissociation.

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