Why Is Nitrogen Used in LC-MS? Is It for Maintaining the Vacuum of the Mass Spectrometer?
In liquid chromatography–mass spectrometry (LC-MS), nitrogen is primarily used as a nebulizing and auxiliary gas during the electrospray ionization (ESI) process to facilitate the formation of an aerosol. Its role involves several critical functions:
Nebulization Assistance
In the ESI source, the sample solution is expelled through a fine nozzle under high pressure to generate microdroplets. Nitrogen acts as a shearing gas that aids in producing smaller droplets, thereby enhancing ionization efficiency.
Evaporation Enhancement
The flow of nitrogen accelerates the evaporation of solvent from the droplets, reducing their size and ultimately enabling the ionization of analyte molecules for introduction into the mass analyzer.
Drying and Desolvation
Nitrogen helps remove solvent from the aerosolized droplets, preventing aggregation or deposition of the analyte and ensuring cleaner and more efficient transfer of the sample into the mass spectrometer.
Inert Atmosphere
As an inert gas, nitrogen contributes to sample stability by minimizing oxidative or other undesirable chemical reactions during the electrospray process.
Regarding vacuum maintenance, nitrogen is not primarily used for this purpose in LC-MS systems. The high-vacuum environment required in the mass spectrometer is maintained by vacuum pumps. Instead, nitrogen mainly supports the ionization and transfer of analytes before they enter the vacuum region of the instrument.
MtoZ Biolabs, an integrated chromatography and mass spectrometry (MS) services provider.
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