Thermospray

Thermospray is a form of atmospheric pressure ionization in mass spectrometry. It transfers ions from the liquid phase to the gas phase for analysis. It is particularly useful in liquid chromatography-mass spectrometry.

Thermospray was originally developed for coupling liquid chromatography to mass spectrometry (LC-MS). Thermospray may be defined as the controlled partial vaporization of a liquid as it flows through a heated capillary tube. The nebulization is accomplished by pumping a liquid sample at moderately high pressure through an electrothermally heated capillary tube. When sufficient power is coupled to the flowing sample stream, a partially vaporized mixture is produced consisting of some fraction of vaporized sample and some remaining liquid sample. Upon exiting the heated capillary, the rapidly expanding sample vapor converts the remaining liquid stream to an aerosol. The vapour so produced acts as a nebulizing ‘gas’ and aids the breakup of the liquid stream into droplets, in a process similar to pneumatic nebulization. Thus, conceptually this can be thought of as a pneumatic process where the expanding solvent vapor is used as a nebulization gas. The solution leaves the tube as a supersonic jet or spray of very small droplets in solvent vapor. Qualitatively, the aerosols appear dense with a moderately narrow particle size distribution.