1 .Prefreezing
During the Prefreeze step, the sample is frozen so that all
the solvent (normally water ) turns to solid (ice).
2. Primary Drying (Sublimation)
In Primary Drying, the ice sublimates or turns directly to
vapour under low pressure (vacuum).
3. Secondary Drying (Desorption)
In secondary Drying the remaining water, not frozen but
bound by molecular bonding to the solute, is removed from the sample.