Method and apparatus for desolvating flowing liquid

摘要

Methods and apparatus for desolvating flowing liquid streams while retaining temporal resolution of dissolved substrates are disclosed. A novel small-scale self-regulating spray dryer preserves temporal resolution while desolvating a liquid chromatography eluent stream and depositing the solute onto an optical surface for infrared spectrographic analysis. The liquid eluent is pumped through a heated nebulizer to create a high-speed jet of solute containing liquid and solvent vapor. This jet is directed circumferentially inside a hot cylindrical cavity. Centrifugal force causes the larger liquid droplets to travel along the outer diameter of the cavity. The cavity surface is heated to cause the droplets to film boil. Film boiling reduces droplet contact with the cavity surface thereby retaining the solute in the droplets. The solute temperature is limited by controlling the pressure into which the solvent evaporates from the droplets. When the droplets are sufficiently small, Stokes drag from the exiting solvent vapor carries the droplets out through the center of the cylindrical cavity. After exiting, the superheated solvent vapor further dries the droplets. Solvent vapor is removed by condensation onto a cooled surface. A freezing point reducing agent may be added to improve removal of solvent condensate. Stokes drag from a non-condensable gas maintains the dried droplets in suspension. This suspension travels through an orifice that focuses the impaction of the dried droplets onto the optical surface for infrared analysis. The deposition surface is in an evacuated chamber and is temperature controlled to freeze liquid solutes yet allowing sublimation of residual solvent.