Principle of operation:- LAESI produces ions for MS analysis under normal atmospheric conditions for samples containing water, The principle of operation can be divided into two steps. 1)- Generation of analyze species:- When a MID-IR laser beam is applied to a target that contains a hydroxide group, the target will absorb energy from this laser beam leading to evaporation of moisture from the targeted area, and a small portion of the sample is ablated into the gas phase, and the plume-like environment is formed. 2)-Reacting analyte species with charged solvent species:- Now the ESI plays an imp role in this part, Electrospray ionization (ESI) source is located above the sample for post-ablation ionization. The jet of ablated material is intersected and ionized by a spray plume from the ESI source located above the sample. Sample get ionized and ionized molecules then transfer towards the mass detector.

1. Laser Ablation Electrospray Ionization
(LAESI)
Kute Raju Dattatray
Department of Analysis
(First year /1st semester)
Reg. No: PA/2022-05/087
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2. Sr.no CONTENT Page no
1 INTRODUCTION 3
2 DISCOVERY 4
3 PRINCIPLE OF OPERATION 5
4 SCHEMATIC REPRESENTATION 6
5 FLOWCHART 7
6 ADVANTAGES/LIMITATION 8
7 APPLICATION 9-12
8 ANIMATION VIDEO 13
9 REFRENCES 14
TABLE OF CONTENT
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3. ESI SOURCE
For ionization
ABLATION
The loss of material from a large
mass of surface as a result of the
action of the external force.
LASER
(Mid-IR 2940nm)
To generate gas phase particle.
LAESI
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4. 4

5. Principle of operation:-
LAESI produces ions for MS analysis under normal atmospheric conditions for samples containing water,
The principle of operation can be divided into two steps.
1)- Generation of analyze species:-
When a MID-IR laser beam is applied to a target that contains a hydroxide group, the target will absorb energy
from this laser beam leading to evaporation of moisture from the targeted area, and a small portion of the sample
is ablated into the gas phase, and the plume-like environment is formed.
2)-Reacting analyte species with charged solvent species:-
Now the ESI plays an imp role in this part, Electrospray ionization (ESI) source is located above the sample for
post-ablation ionization. The jet of ablated material is intersected and ionized by a spray plume from the ESI
source located above the sample.
Sample get ionized and ionized molecules then transfer towards the mass detector.
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6. Schematic representation of laser ablation electrospray ionization (LAESI)
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7. Sample put on sample
stage
IR beam was
bombarded on it
Sample absorb energy
and ablation occur
Ablation ejects mixture of
molecule from sample
Ionisation of sample molecule
Ionised molecules passed
to the MS
ESI source
We pass solvent of
interest through it
Extensive evaporation
is occurred
Intersection occur between ablated
sample and aerosol from ESI
Jet of aerosol was
formed
Flowchart of operational principle of LAESI
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8. Advantages:-
 This technique needs very little or no sample preparation.
 It has high sensitivity.
 This ionization technique does not need any kind of external matrix.
 This ionization technique can be carried out in natural and uneven biological surface.
 It allow direct analysis of sample in native atmospheric condition .
 Required significantly shorter analysis time.
Limitation:-
LAESI is a relatively new technique for those samples which contain water and are relatively stable. However, it has
limitations for those samples which have lower water content.
For example,
• this technique does not ionize dry skin, nails, teeth, and bone well; this is due to the low water content in these samples.
• It needs a relatively large sampling area compared to some other common ionization techniques.
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9. Applications:-
 LAESI help us in a broad variety of applications ranging from plant biology to clinical analysis.
 It is possible to performed in vivo spatial profiling (on leaf, stem, and root nodule ) of plant with the help of LAESI.
 For detection of mycotoxin produced by a variety of molds, particularly Aspergillus Often found in rotting apples.
 Proteins, lipids, and metabolites were Easily identified.
 LAESI can also go for direct analysis of bodily fluids like (urine, blood, and serum) respectively.
 LAESI-MS applicability was demonstrated in the analysis of tissue, food contaminants, synthetic materials, and
single cells analysis also.
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10.  This technique is able to performed in vivo spatial profiling on leaf, stem, and root of the plant.
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11.  Patulin is a toxin produced by a number of different moulds such as Penicillium and Aspergillus. It can be found in
damaged or mouldy fruits, particularly apples.
 Patulin was not detected in the control samples but was seen in all mold-infected fruits.
 With the used of LAESI we are easy to detect and quantify the limit of toxin in infected fruit.
Detection of toxin by LAESI
 For detection of mycotoxin produced by a variety of molds, particularly Aspergillus Often found in rotting apples
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12. a) Optical image of the
Soybean nodule with small
ablation hole of diameter 150
μm.
b) The intensities of m/z ratio
Red-1069.56 (Soyasaponin)
Green-616.178 (Heme).
c) Average mass spectrum from the
outer layer for 1-45 Laser pulse
[soyasaponin H]+ revealed high
abundance in the first 45 laser shots
after the laser was pulsed.
d) Average mass spectrum from 50-
90 Laser pulse
Within the same experimental run,
ions localized to the infection zone
[heme B]+ .
Molecular species tracked to the outer layer included :-
 (soyasaponin -- m/z 1069.551)
 (dihydroxy Methoxyflavone --m/z 285.071)
Within the infection zone several ions were localized,
 (Heme B+ -- m/z 616.179)
 (Adenosine -- m/z 268.104)
Here, LAESI localized specific ions to the different layers of soybean nodule and tracked them by observing
the ion intensity over the number of laser shots .
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14. Reference:-
1) Nemes P, Vertes A. Laser Ablation Electrospray Ionization Mass Spectrometry: Mechanisms,
Configurations and imaging Applications. Ambient Ionization Mass Spectrometry. London: Royal
Society of Chemistry. 2014 Nov 14:348-71.
2) Nemes P, Vertes A. Laser ablation electrospray ionization for atmospheric pressure, in vivo, and
imaging mass spectrometry. Analytical chemistry. 2007 Nov 1;79(21):8098-106.
3) Etalo DW, DeVos RC, Joosten MH, Hall RD. Spatially resolved plant metabolomics: some potentials
and limitations of laser-ablation electrospray ionization mass spectrometry metabolite imaging. Plant
physiology. 2015 Nov;169(3):1424-35.
4) Shrestha B,Vertes A. In situ metabolic profiling of single cells by laser ablation electrospray ionization
mass spectrometry. Analytical chemistry. 2009 Oct 15;81(20):8265-71.
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16. the ionization efficiency achieved by laser sources is low, as the majority of desorbed molecules generated by the
laser ablation process are neutrals Therefore, most laser-based ambient ionization MS techniques are coupled to a
secondary ionization source, such as ESI to enhance ionization efficiency and thus sensitivity.
LAESI utilizes a mid-IR laser to ablate a sample surface, generating a plume of mostly neutral molecules. As with
other ESI based methods, ionization is favored toward polar molecules. LAESI analysis of polar and less-polar
analytes including verapimil and arginine during the same experiment has been achieved by optimizing a solvent
gradient in the ESI source.
Polar molecule
Water (H2O) is polar,
Ammonia (NH3) is polar,
Sulfur dioxide (SO2) is polar,
Hydrogen sulfide (H2S) is polar.
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