Filtration, Solid phase extraction

Filtration is accelerated either with pressure or with the aid of vacuum. The vacuum regulation and ultimate vacuum requirements are generally low. If it is filtered at 80 mbar, 92% of the atmospheric pressure is available as the driving force for filtration. Excess vacuum (e. g., from rotary vane pumps) can even cause evaporation of solvents instead of just liquid flow.

Process requirements

very modest ultimate vacuum, no more than average requirements
adequate vacuum flow rate, depending on the filter size, leak rate, condition of the filter cake, and whether a filtration manifold may be used to operate more than one filter at a time
simple, manual vacuum regulation

Demands made of the vacuum pump

single- or two-stage diaphragm pumps with as much as 70 or 7 mbar ultimate vacuum are ideal
excellent chemical and condensate compatibility for filtration or extraction of samples containing solvents
pump protection from particles and droplets of liquid with a suction-side separator (AK)
an exhaust condenser to minimize pollution of the environment and laboratory air from solvent vapors
chemistry pumping units that are equipped with electronic vacuum controllers shut off pump when filtration is complete