Field desorption

BY ABDUL QAYOOM MUGHERIABDUL QAYOOM MUGHERI

Mphil scholarMphil scholar

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Introduction Experimental techniques

Ionization sources Mechanism Comparison FD and FI

Advantages ApplicationsConclusionAcknowledgment

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Field desorption has been considered as offspring of field ionization and thus the principles governing the ion formation have traditionally been treated in more or less similar way.

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DesorptionRemoval of a substance from a surface on which it is adsorbed

FD was developed by H.D.Beckey in 1969.

A term used to describe the formation of ions in the gas phase from a material deposited on a solid surface (known as an 'emitter') in the presence of a high electrical field. 

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The development of the experimental techniques of field desorption- MS Various types of emitter different sample loading techniques are also.

Automatic FD emitter heating devices and laser assisted.

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•Suitable for high molecular mass and/or thermally labile substances such as polymers, peptides, carbohydrates and organic or inorganic salts.

•A solution of the sample is applied to the emitter before it is introduced into the ion source.

•The emitter is mounted on the tip of the axial sample introduction probe.

Field Desorption analyses feature the following:

Field Ionization – gas is passed over ionization source

Field Desorption – dipped in solution containing sample and placed back in spectrometer

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Field ionization (FI) is a method that uses very strong electric fields to produce ions from gas-phase molecules.

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FI FD

Sample is heated in a vacuum so as to volatize it onto an ionization surface.FI is suited for use with volatile, thermally stable compounds.

The sample is placed directly on to the surface before ionization.FD is used for nonvolatile compounds or thermally labile substances.

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FD is perfectly suited for the analysis of synthetic polymers or man made polymer.

examples . Poly siloxane,poly phospazene,Backelite,Nylon etc.

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It was the major advance development of field desorption Mass spectrometry. It was introduced by H. B. Linden in 2000.

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Liquid injection FD ionization a new tool for soft ionization of sample include non polar H/Cs.

FD M-S is used to investigate almost any major class of organic and in-organic.

the main targets are substances which cann,t be evaporized undecomposed prior to ionization.

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FD MASS SPECTROMETRY APPLIED TO COAL RESEARCH

The fossil fuel research program has greatly benefited from the availability of on-site.

The applications include (a)differentiating coal types (b) analyzing coal tars, (c) determining the fate of a nitrogen-containing donor solvent in coal (d) identifying species responsible for catalyst deactivation.

Many earlier applications of FD to analysis the polar and nonvolatile analytes such as polymers and biological molecules.

FD can produce simple mass spectra with molecular information from hydrocarbons and other particular analytes.

It is important in pharmaceutical,biochemistry and medicine.

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1. Low Typically less than 1000 Da.in FI

2. . Low-moderate, depends on the sample. Typically less than about 2,000 to 3,000 Da.in FD

3. Some examples have been recorded from ions with masses beyond 10,000 Da

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FD was virtually unique in being able to ionize non volatile polar organic and inorganic molecules.

Simple mass spectra,typically molecular like ion species per compound.

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1. Field desorption mass spectrometry by laszlo prokri

2.  Beckey H.D. Field ionization mass spectrometry. Research/Development, 1969, 20(11), 26

3.  HB Linden, Liquid injection field desorption ionization: a new tool for soft ionization of samples including air sensitive catalysts and non-polar hydrocarbons, Eur. J. Mass Spectrum. 2004, 10, 459-468

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thankful to Almighty Allah Who provided me this fabulous opportunity.

I am grateful to Prof:Dr. Shahabuddin Memon for his precious unassuming efforts and I am thankful to my classmates for wonder Co-operation.

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