Sterile filtration other filters

The essential method to obtain sterile air, whether packed-bed or cartridge filters are used, is to reduce the humidity of the air after compression so that the filter material always remains dry. The unsterilized compressed air must never reach 100% relative humidity. Larger plants install instrumentation with alarms set at about 85% relative humidity. Careful selection of the cartridge design or the design of packed-bed filters will result in units that can operate in excess of three years without replacement of filter media. If a fiber material is used in a packed-bed type filter, the finer the fiber diameter the shallower the bed depth needs to be for efficient filtration. Other filter media are less common and tend to have special problems and/or shorter life. The bed depth of filters is only 10 to 18 inches for fibers of less than 10 microns. These filters run clean for 2 weeks or longer before being resterilized. 

Injections and infusion fluids must be manufactured in a manner that will minimize or eliminate extraneous particulate matter. Parenteral solutions are generally filtered through 0.22 pm membrane filters to achieve sterility and remove particulate matter. Prefiltration through a coarser filter is often necessary to maintain adequate flow rates, or to prevent clogging of the filters during large-scale manufacturing. A talc or carbon filtration aid (or other filter aids) may also be necessary. If talc is used, it should be pretreated with a dilute acid solution to remove surface alkali and metals. 

Membrane polymeric materials for separation applications are made of polyamide, polypropylene, polyvinylidene fluoride, polysulfone, polyethersulfone, cellulose acetate, cellulose diacetate, polystyrene resins cross-linked with divinylbenzene, and others (see Section 2.9) [59-61], The use of polyamide membrane filters is suggested for particle-removing filtration of water, aqueous solutions and solvents, as well as for the sterile filtration of liquids. The polysulfone and polyethersulfone membranes are widely applied in the biotechnological and pharmaceutical industries for the purification of enzymes and peptides. Cellulose acetate membrane filters are hydrophilic, and consequently, are suitable as a filtering membrane for aqueous and alcoholic media. 

Sterilization and Particle Removal (Pharmaceuticals). A great many of the drugs and solutions produced by the pharmaceutical industry or made up in the hospital pharmacy have to be both sterile and relatively free of particulate mat-ter-especially if the product is to be injected into the bloodstream. For drugs and other products that will not withstand heat, sterilizing filtration is the only alternative. Tissue culture media, parenteral solutions, vaccines, human plasma fractions, antibiotics, diagnostic injectables are all sterilized by membrane filters. 

MF is also used to remove microorganisms and particulates from air and other gases used in the pharmaceutical industry. Some specific applications include vent filters filtration of compressed air used in sterilizers, filtration of air or nitrogen used for solution transfers or at filing lines, and filtration of air or nitrogen used in fermentors. 

There are certain things that must be done by filter users as part of validation before using a particular type of Tiller other tests have to be done before and/or after use of each individual filter and yet other indicators ought to be monitored throughout use of Individual filters. The distinction between validation and routine monitoring is less clear for sterile filtration than for any other sterilization process. 

Owing to the potential additional risks of the filtration method as compared with other sterilization processes, a double filter layer or second filtration via a further sterilized microorganism-retaining filter immediately prior to filling may be advisable. The final sterile filtration should be carried out as dose as possible to the filling point... 

Analytical and industrial filter papers are usually made from cotton, dissolving pulps, glass microfibers or other artificial fibers. They possess a uniform stock distribution and, thus, a homogeneous pore size. Analytical filters are acid washed and are made without paper making additives. Filter layers with a basis weight of up to about 750 g m are produced to withstand special stress, e. g., in the beverage industry. Filter layers of this type, that are also used for sterilization filtration, must comply with food laws. For industrial use, the paper and filter layers may also be impregnated with melamine-urea resins or similar compounds. 

In 1916 the sterile filter sheet became available for sterilizing filtration for the beverage and dairy industries. Other applications were soon found for this material, including vaccines, cosmetics, sugar, ink, film and paint processing. Today, however, asbestos is no longer used in the manufacture of filter sheets because of its toxicity. Considerable research has resulted in the availabihty of asbestos-free filter sheets that utihze cellulose fibres and mixtures of natural (uncalcined) kieselguhr and perlite. Other types of sheet also incorporate an advanced resin system. 

Although organic substrates such as carboxylic acids are thermally stable and may be sterilized with the basal media, many others including, for example, carbohydrates, esters, or amides are better prepared as concentrated stock solutions, sterilized by filtration through 0.22 pm filters and added to the sterile basal medium. 

The vast majority of Washington wine is filtered through nonasbestos filter pads. In preparing the wine for bottling, the S02 levels employed will vary depending upon whether or not the winery utilizes membrane filtration and/or some other form of wine sterilization. One major winery bottles its wine at 35 mg/L free S02 with the addition of200 mg/L of sorbate followed by a membrane filtration. Many of the small wineries lack a source of steam or... 

One of the most important sensors needed is one that reliably monitors cell density. An IR fiber-optic cell density probe has been used for this because it can directly monitor cell growth (without dilution) in high-cell-density bacterial fermentations. The ability to do an online sample filtration through the use of hollow fibers or rotating filters has made possible continuous, online measurement of glucose, lactate, and other metabolites. However, glucose, nitrogen substrate, and phosphate sensors that can withstand repeated system sterilization are still needed. 

Sterile filter compatibility testing. It should be demonstrated that filters of the same surface area as for commercial batches are compatible with the formulation being filtered [16]. The filter should not induce significant degradation of the active product or leach out undesirable substances. The retention of active material inside the filter, in other words the loss on filtration, should be quantified and assessed statistically. 

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