Fundamentals of Filtration

Filtration is a technique that utilizes a porous barrier to separate suspended or dissolved materials in solution based on size or molecular weight, eliminating the need for centrifugation, solvent phase changes or other product damaging methods. Application of positive or negative pressure differential across the selectively permeable barrier drives the separation in a sieve-like manner. Smaller constituents pass through the barrier with the solvent as filtrate while the larger solutes are retained. The type of filtration is based on the retentate and pore size. Spectrum offers a complete range of separation filters for macrofiltration, microfiltration and ultrafiltration applications.


Being the simplest and least expensive, macrofiltration is conventionally defined as the filtration of particles that are 5 µm or greater. Spectrum offers a large assortment of Spectra Mesh® screens in several polymer types with mesh opening sizes ranging from 5 µm to 1 mm to handle just about any macrofiltration need.
Laboratory Macrofiltration


Originally described as the separation of particles or microbes that could be seen with the aid of a microscope (cells, macrophage, large virus particles, cellular debris), microfiltration (MF) pertains to separations with the membrane pore size ranging from 0.05 to 0.5 µm in diameter. Spectrum offers three types of hollow fiber tangential flow MF membranes with pore sizes ranging from 20 nm to 0.5 µm and surface areas ranging from 6 sq. cm to 13.9 sq. m.
Laboratory Microfiltration     HF TFF Microfiltration


Since the "molecular shape" of dissolved solutes ranging from 1 to 1,000 kD significantly affects the retention characteristics, the pore rating for ultrafiltration (UF) membranes is indirectly determined as the nominal molecular weight cut off (MWCO) that is retained by approximately 95%. Spectrum offers low protein binding polysulfone hollow fiber membranes with 10 kD, 50 kD, 400 kD, 500 kD (20 nm) and 1,000 kD (0.05 µm) and surface areas ranging from 8 sq. cm to 5.1 sq. m.
HF TFF Ultrafiltration

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