Particle Beam Interface:

It employs helium gas to nebulize the mobile phase, producing an aerosol from which the sample is evaporated at near ambient temperature and pressure. Thus, it consists of three sections; aerosol generator, desolvation chamber and two stages aerosol-beam pressure reducer. The mixture of He, solvent vapor and analyte molecules is accelerated into a low pressure two stage momentum separator where it expands supersonically. The two stage aerosol-beam separator consists of two nozzle and skimmer devices which reduce the pressure from an initial value close to atmospheric pressure in the desolvation chamber to a final value close to the pressure in the ion source. In the desolvation chamber maintained at room temperature, solvent evaporates. The separator allows solute particles from the initial aerosol to be preferentially transferred through the system while dispersion gas and solvent vapor are pumped away. After He and solvent are pumped off, the heavier analyte molecules pass directly through two skimmer plates and along a narrow probe into a heated ionization chamber where electron impact (EI) ionization occurs.