Concentrators (aka nitrogen evaporators or nitrogen blowdown concentrators) are a valid alternative to rotary evaporation mainly in case of small volumes (under 50 mL) and a large quantity of samples.
Concentrators accelerate the evaporation by decreasing the partial vapor pressure of the solvent just above the surface of the liquid. Blowdown evaporators use a jet of gas to continually force off the layer of air that is saturated with vapor. By immediately removing molecules that enter the vapor state, the molecules do not have a chance to return to the liquid, which increases the evaporation rate. As said blowdown technique is very useful for small sample volumes because with larger samples nitrogen blowdown will take longer and semi-volatile compounds may be lost. Since the samples are immersed in a water bath, with programmable temperatures up to 100°C, the evaporation is further accelerated. LabTech offers 4 models, 3 of them automated and one manual, hosting different tube sizes to satisfy multiple needs.