Chemical Compatibility
Many of the membranes manufactured by Millipore are used in drug preparation, specifically parenteral (injected) drugs, and are subject to very high quality standards. Even if the monoclonal antibody is going to be used in a diagnostic kit, it must be a pure, consistently reproducible preparation.
Because of these high standards, Millipore and other membrane manufacturers must demonstrate that their filters are not introducing anything into the filtration stream. Extractables and endotoxins are typically measured. Most Millipore filters carry a USP class VI certification, assurance that these filters are compatible with biological systems.
Sample Stream Compatibility
Filter material must be compatible with the chemical nature of the sample stream under the conditions that the filtration will be performed. This will minimize the risk of structural failure during filtration.Membranes used in the filtration of organic solvents must be resistant to those solvents. If the membrane dissolves in the filtration process, that membrane will be totally useless in filtering those solvents.
When selecting a filter, determine if constituents in the sample will chemically attack the filter. If the filter undergoes chemical degradation, it may release foulants into the sample stream.
The same is true of an aqueous stream. Care must be taken that the filter not be damaged by the aqueous stream. Most membrane polymers are resistant to standard water. Issues arise when the pH of the water is incorrect, or when additives chemically attack the polmer.
Determine if the filter is sensitive to extremes of pH and compatible with specific acids and bases. Chemical attack at extremes of pH may take time to appear and could be problematic well before filtration is completed.
Determine if constituents in the sample will dissolve the filter material. Different from chemical degradation, this risk relates primarily to organic solvents that are capable of solubilizing the polymer from which the filter is made. Some polymers exhibit better solvent resistance than others. The chemical compatibility chart provides general guidelines on the use of specific solvents. Some solvents may be incapable of dissolving the filter, but could be absorbed into the polymer matrix causing it to swell over time and altering the effective pore size of the filter and changing its performance.
Although chemical compatibility usually deals with the liquid phase of the sample, dissolved solutes may interact with the membrane in an undesirable manner. The solute of interest should not be adsorbed onto the surface of the filter. Most polymers used to make filters are highly adsorptive for biomolecules and will bind them out of the sample stream until the polymer surface is saturated. If a low binding surface is required, this property should be specified during the selection process.
In venting applications, hydrophobicity of a filter is used to allow release of air bubbles from a liquid stream. The sample stream should not contain detergents or solvents that will wet out the surface of the filter.
Sterilization
When other companies put Millipore membranes into the medical devices that they manufacture, sterilization of the entire device is part of their standard process. So, Millipore membranes must also be able to maintain their integrity in a variety of sterilization processes [ II.A.8 ] that use ethylene oxide, gamma radiation, and autoclaving.More Information
For more information on the chemical compatibility of filters and filtration components, see: