Field desorption

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Field desorption

Field desorption (FD) is a method of ionization in mass spectrometry (MS) where a sample is ionized by placing it on a conductive surface that is then subjected to a high electric field. The high electric field causes the desorption and ionization of the sample molecules from the surface, allowing them to be analyzed by the mass spectrometer. FD is particularly useful for the analysis of high molecular weight and thermally labile molecules that are difficult to ionize by other methods.

The principle behind field desorption is based on the creation of a strong electric field at the surface of an emitter, typically made of a metal or graphite. The emitter is coated with the sample to be analyzed and is then placed in the vacuum system of the mass spectrometer. When a high voltage is applied to the emitter, the strong electric field that is generated causes the molecules of the sample to ionize and desorb from the surface. These ions are then accelerated into the mass analyzer of the spectrometer for detection and analysis.

Field desorption is particularly noted for its soft ionization capabilities, meaning it tends to produce ions without causing fragmentation of the molecules. This makes FD an invaluable technique for the analysis of large biomolecules, such as proteins, peptides, and polymers, where maintaining the integrity of the molecule is crucial for accurate analysis.

One of the limitations of field desorption is the requirement for the sample to be conductive or to be made conductive, often through the addition of a matrix or salt. Additionally, the technique requires a high degree of expertise to prepare the emitter and to optimize the conditions for ionization, which can limit its use in some laboratories.

Despite its limitations, field desorption has found applications in various fields, including biochemistry, polymer science, and pharmaceuticals, where it is used to analyze complex mixtures and to determine molecular weights and structures of large molecules.

Field desorption Resources
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