Millipore Separation and Purification Technologies

Millipore Separation and Purification Technologies Millipore technology provides products, systems and application techniques for the analysis and purification of fluids by filtration through microporous and ultrafiltration membranes . Millipore microporous membrane and depth filtration has long been an integral and critical step in industrial processing. In pharmaceutical manufacturing, membrane and depth filters remove particles, viruses, colloids, bacteria, and other types of cellular organisms from solutions throughout the process, from the purification of central system water to final product sterilization. Microporous membranes may be operated on normal flow (dead-ended) or tangential flow (cross-flow) filters for a broad range of solid/liquid or solid/gas separations. Millipore membrane filtration is also widely used as an analytical tool for the collection, identification and measurement of particles and microorganisms. Millipore ultrafiltration membranes are operated in tangential flow filters and are used for molecular and viral separations. They are used to concentrate and purify a wide variety of biological and chemical process fluids, to concentrate and purify or remove viruses and other colloid suspensions, and to remove very fine particulate contamination for fluid clarification.

Microfiltration
Microfiltration is the process of removing contaminants in the 0.025 to 10.0 µm range from fluids by passage through a microporous medium such as a membrane filter. Although micron-sized particles can be removed by use of non-membrane or depth materials such as those found in fibrous media, only a membrane filter, having a precisely defined pore size, can ensure quantitative retention.

The retention boundary defined by a membrane filter can also be used as an analytical tool to validate the integrity and efficiency of a system. For example, in addition to clarifying or sterilizing filtration, fluids containing bacteria can be filtered to trap microorganisms on the membrane surface for subsequent culture and analysis.

Membrane filters can be used for final filtration or prefiltration, whereas a depth filter is generally used in clarifying applications where quantitative retention is not required, or as a prefilter to prolong the life of a downstream membrane.

Membrane and depth filters offer certain advantages and limitations, and can complement each other when used together in a microfiltration process system.

In all filtration applications, the permeability of a filter medium can be affected by the chemical, molecular or electrostatic properties of the filtrate.


Ultrafiltration
Ultrafiltration is the process of separating extremely small particles and dissolved molecules from fluids. The primary basis for separation is molecular size although secondary factors such as molecule shape and charge can play a role. Materials ranging in size from 1,000 to 1,000,000 molecular weight are retained by ultrafilter membranes, while salts and water will pass through. Colloidal and particulate matter can also be retained.

Ultrafiltration membranes are used to purify and collect both material passing through the filter and material retained by the filter. Materials smaller than the pore size rating pass through the filter and can be depyrogenated, clarified and separated from high molecular weight contaminants. Materials larger than the pore size rating are retained by the filter and can be concentrated or separated from low molecular weight contaminants.

Ultrafiltration membranes are usually operated in a tangential flow mode—feed material sweeps tangentially across the upstream surface of the membrane as filtration occurs— thereby maximizing flux rates and filter life. These systems offer the advantage of long life because ultrafilter membranes can be repeatedly regenerated with strong cleaning agents.

Microporous membranes can also be operated in a tangential flow mode. This provides the ability to purify and concentrate particulate materials, such as bacteria, yeast, and animal cells where large molecules must pass through the filter.


Chromatography
Millipore now also offers liquid chromatography for pharmaceutical and biotech applications, for the purification of proteins, enzymes, peptides and other biologics and synthesized organic molecules.
 
Millipore has an extensive product range, through media, columns and systems for LPLC and HPLC, from laboratory to process scale, offering a single source for all the key elements of chromatographic processes.


Depth, Surface, and Membrane Filters
For most high volume filtration applications, the properties of membrane and depth filters are clearly complementary. Depth filtration allows the removal of a bulk of particles economically. Surface filtration combines relatively high dirt-holding capacity with clearly defined retention characteristics. Membrane filtration permits complete removal of particles and micro organisms above a certain size as qualified by preestablished specifications and testing regimen. By using a depth filter for upstream processing and a membrane filter for final filtration, it is possible to get an optimum combination of retention efficiency, high dirt capacity and processing economies.


Depth Filter
Structure
Depth filters have a fibrous, granular or sintered matrix that produces a random porous structure. Particles become trapped in the tortuous network of flow channels. The principle retention mechanisms are random adsorption and mechanical entrapment throughout the depth of the matrix.

Construction
Filtration media may be wound cotton, polypropylene, rayon cellulose, fiberglass, sintered metal, porcelain or diatomaceous earth.

Performance
Depth filters characteristically exhibit high dirt-holding capacity and will also retain a large percentage of contaminants smaller than their pore size rating. They are generally less expensive than membrane filters.


Surface Filter
Structure
Surface filters have a multilayer filter medium constructed of glass or polymeric microfibers. Particles larger than the spaces within the filter matrix are retained, primarily on the surface. Smaller particles tend to be trapped within the matrix, giving the surface filter properties of both a membrane and a depth filter.

Construction
Typically, surface filters are constructed of polypropylene, cellulose/resin bonded paper , or fiberglass/paper.

Performance
Due to their multiple layers of pleated media, surface filters exhibit a high dirt-holding capacity. As a result of their “controlled” pore structure, they provide more predictable retention than depth filters. They are generally less expensive than membrane filters.


Membrane Screen Filters
Structure
Membrane filters may be thought of as a geometrically regular porous matrix. Particles are retained on the surface or within a given fraction of the membrane's thickness, primarily by a size exclusion (sieving) mechanism. All particles and microorganisms larger than the pore size will be retained.

Construction
For critical submicronic and macromolecular separations, these filters are constructed of cast polymeric membranes.

Performance
Predetermined, controllable pore size limits the largest particle than can pass through a membrane filter. Retention efficiency is independent of flow rate and pressure differential. Membrane filters exhibit low hold-up volume and are non-fiber releasing.