Laser Desorption Mass Spectrometry
Definition and meaning of Laser Desorption Mass Spectrometry in chemistry.
Laser desorption mass spectrometry (LDMS) is an analytical technique that uses laser radiation to directly desorb and ionize molecules from a solid sample surface, which are then separated and detected based on their mass-to-charge ratio.
In more detail
In LDMS, a focused laser beam (typically ultraviolet or infrared) strikes the sample surface, causing molecules to leave the solid phase (desorption) and become ionized in the process. The resulting gas-phase ions are accelerated into a mass analyzer where they are separated by their mass-to-charge ratio. This technique is particularly valuable for analyzing heat-sensitive or non-volatile compounds that cannot be easily vaporized or ionized by conventional methods. Because it is used without a matrix, LDMS works best on small to moderately sized molecules; very large biomolecules such as intact proteins tend to fragment excessively or ionize poorly without a matrix to cushion energy transfer, which is why matrix-assisted variants (MALDI) were developed for that size range. LDMS requires minimal or no sample preparation, making it useful for surface analysis of small organic molecules, lipids, and synthetic polymers.
Key facts
| Abbreviation | LDMS |
|---|---|
| Typical laser wavelength | Ultraviolet (UV) or infrared (IR) |
| Key advantage | Direct analysis of solid samples with minimal or no preparation |
| Field | Analytical Chemistry |
LDMS can be used to analyze small organic molecules and lipids directly from a polymer or tissue surface without chemical derivatization, allowing rapid on-surface molecular identification in materials science and forensic analysis.
Frequently asked questions
How does LDMS differ from MALDI?
MALDI (matrix-assisted laser desorption/ionization) uses a matrix compound to assist desorption and ionization, while direct LDMS desorbs and ionizes the sample without a matrix, allowing analysis of smaller molecules and materials that interact poorly with matrices.
What types of samples are suitable for LDMS?
LDMS works well with solid samples such as small organic molecules, lipids, polymers, minerals, and other compounds that are heat-sensitive or poorly ionizable by conventional electrospray or electron ionization methods. Very large biomolecules such as intact proteins are typically better suited to matrix-assisted methods like MALDI.