Filter selection compatibility

Filter Selection. A variety of product- and process-related factors govern filter selection. Considerations include the characteristics of the fluid to be filtered, ie, its chemical composition and compatibility with the filtration system (inclusive of the membrane, filter hardware, piping, etc), the level of bioburden present, specifications on effluent quality, the volume of product to be filtered, flow rate, and temperature. 

Among the more important factors that must be taken into consideration when choosing a filter for a particular application are the size, shape, and hardness of the particles to be removed, the quantity of those particles, the nature and volume of the fluid to be filtered, the rate at which the fluid flows, whether the flow is steady, variable, and/or intermittent, the system pressme and whether that pressme is steady or variable, the available differential pressme, the compatibility of the medium with the fluid, the fluid temperatme, the properties of the fluid, the space available for particle collection, and the degree of filtration required. Let s examine how some of these factors affect filter selection. 

The main principles of instrument design are summarized in Table 10.23. In filtration, e.g. for gravimetric analysis, selection of filter material (Table 10.22) requires careful consideration in terms of application, strength, collection efficiency, compatibility with pump, water uptake, etc. Humidity-controlled balance rooms, iTiicrobalances and careful handling techniques may be required. 

The formulator must be aware of the potential for binding when filtering protein solutions. Because of the cost of most protein materials, a membrane should be used that minimizes protein adsorption to the membrane surface. Typical filter media that minimize this binding include hydrophilic polyvinylidene difluoride and hydroxyl-modified hydrophilic polyamide membranes [17a]. Filter suppliers will evaluate the compatibility of the drug product with their membrane media and also validate bacterial retention of the selected membrane. 

This mass separator is a new type, especially accommodated to be compatible with the 2V2-D geometries available in this fabrication process. The synchronous ion shield (SIS) analyzer selects the mass, for which the filter is transparent, by a traveling high frequency rectangular pulse stream (rise and fall time <1 ns) of a swept frequency (0-270 MHz), which is supplied to a comb shaped electrode arrangement. 

The selection of materials for the ink should take into consideration the compatibility of each ink component with the construction materials it meets. These materials can be very different, starting from metallic parts (orifice plate, sensors, fittings, filters, etc.) which may degrade upon contact with a high or low pH medium and plastic... 

The most important consideration in the selection of the filter is the compatibility of the hlter materials of constmction with the solvent. The solvents used in pharmaceutical processes can be very aggressive. They include acetone, methanol, ethanol, isopropyl alcohol (IPA), acetonitrile, dimethyl acetamide, dimethyl formamide (DMF), ethyl acetate, tetrahydrofuran (THF), methyl isobutyl ketone (MIBK), and methyl ethyl ketone (MEK). Filters with PTFE membranes and polypropylene supports are used in most applications. 

Proper selection of the filter medium is more of an art than a science. The filter cutoff must be chosen to capture the smallest particles of interest. Other factors that must be considered are the type of filter (bulk or surface), the required flow rate, and the size of the membrane. These parameters are not independent and the best choice will usually involve trade-offs. Finally, the material from which the filter is made must be considered. It must be selected for compatibility with the intended postfiltration processing. Glass-fiber filters, for example, often have very high blanks for common ions such as chloride and sodium. 

Membrane filtration application to biopharmaceutical product development is extremely important since sterile protein-peptide products can only be prepared via sterile filtration and gamma radiation steam cannot be used under pressure. There are several excellent works in the field of sterile membrane filtration.34-36 The filter media most often tested for protein formulations with minimum adsorption and maximum compatibility are mixed esters of cellulose acetate, cellulose nitrate, polysulfone, and nylon 66. Membrane filters must be tested for compatibility with the active drug substance and selected for formulations if they have the lowest adsorption and maximum compatibility with the product. 

Finally, Chapter 12 describes initial studies on biological applications of porous SiC. Free-standing porous membranes are explored as particle-size-selective semi-permeable membranes for filtering of macro (bio-) molecules. SiC s hardness makes it chemically inert and bio-compatible... 

In selecting a membrane material, its pH compatibility and wettability should be considered. Some hydrophobic membranes require prewetting with a low-surface-tension solvent such as alcohol, whereas cartridges containing membranes are often presterilized using gamma irradiation. Such filter systems do not require assembly and steam sterilization. 

Check for chemical compatibility with the filters used in the system before selecting a sanitizing agent... 

The need for chemical compatibility and removal of particulates by filtering are fundamental requirements that should be anticipated during the module design process. A large body of information is available to guide proper materials selection, and there are many adequate filter means commercially available. 

The GC detector is the last major instrument component to discuss. The GC detector appears in Fig. 4.7 as the box to which the column outlet is connected. Evolution in GC detector technology has been as great as any other component of the gas chromatograph during the past 40 years. Among all GC detectors, the photoionization (PID), electrolytic conductivity (EICD), electron-capture (ECD), and mass selective detector (MSD) (or quadrupole mass filter) have been the most important to TEQA. The fact that an environmental contaminant can be measured in some cases down to concentration levels of parts per trillion (ppt) is a direct tribute to the success of these very sensitive GC detectors and to advances in electronic amplifier design. GC detectors manufactured during the packed column era were found to be compatible with WCOTs. In some cases, makeup gas must be introduced, such as for the ECD. Before we discuss these GC detectors and their importance to TEQA, let us list the most common commercially available GC detectors and then classify these detectors from several points of view. 

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