Thermospray Method:

It depends on the thermal generation of a spray and separated heat treatment of that spray to yield desolvated ions. The HPLC effluent is fed into a micro furnace, a capillary tube maintained at up to 400 ^oC that protrudes into a region of reduced pressure. The heat creates a supersonic expanding aerosol jet containing a mist of fine droplets of solvent vapor and sample molecules. The droplets vaporize on their way downstream. The excess vapors are pumped away by an added mechanical pump directly coupled to the ion source. No external ionizing source is required to achieve molecular ions from many nonvolatile solutes at the sub-nanogram level. The ions of sample molecule are formed in the spray either by direct desorption or by chemical ionization when used with polar mobile phase containing appropriate buffer such as ammonium ethanoate. With weakly ionized mobile phase, a conventional electron beam is used to provide gas phase reagent ions for the chemical ionization of solute molecules. Chemical ionization (CI) spectra are typically accompanied by electron- impact spectra. The ions formed are led into a quadrupole or magnetic sector mass spectrometer as shown in Figure(a). An electron beam is used to enhance the production of ions by CI.