In addition to the chemical reagents used to manufacture pharmaceutical active ingredients, the solvents used during synthesis must be filtered before being transferred to the reactor. Water and other utility fluids are also subject to filtration operations upstream of the API production line.
Filtration of raw materials and solvents
This pre-filtration of chemical reagents and solvents used during synthesis takes place during transfer from storage tanks to the reactor.
The filters used must be able to withstand the temperature and pressure conditions present throughout the API production line.
They must also comply with French, European and international regulatory requirements.
Finally, it is essential to select filter housings and filter elements that are compatible with all the chemicals and solvents used. In some cases, for instance, it may be impossible to use standard stainless-steel filter housings.
Filtration of utilities
Utilities refer to the fluids required for the operation of the industrial facility: water, steam (high and low pressure), nitrogen and compressed air.
Liquid water
The European Pharmacopoeia defines three levels of water purification, distinguished mainly by their increasing microbiological purity: purified water, highly purified water and water for injectable preparation. The type of water to be produced and used therefore depends on the specific applications.
The filtration processes implemented to produce pharmaceutical-grade water operate on two levels:
- Particulate filtration, which removes insoluble particles
- Microbiological filtration, which controls biological loads (bacteria, endotoxins, etc.)
The filter housings and filter elements (cartridge filters, filter bags, etc.) must therefore meet different technical and legal requirements depending on the intended type of filtration.
The filter elements must also be able to be replaced regularly during production cycles.
Finally, as water demand is typically high and storage capacity limited within facilities, the flow rates to be filtered are often significant, reaching several m³/h.
Steam
The piping, tanks and equipment used in API manufacturing are often sterilised in place using steam.
This steam must be filtered to remove particles that could contaminate pharmaceutical products and damage the filters present in the API production chain.
Typically, sintered stainless-steel filtration elements are used, offering high thermal and mechanical resistance as well as high porosity, with absolute filtration thresholds down to the micron level.
Other gas
The gases used in the pharmaceutical industry must also be filtered — both to protect processing equipment in the production chain (such as control valves), and to prevent any bacterial contamination via these gases.
To meet the first objective, absolute-rated filters with thresholds in the micron range are used. These exploit the Brownian motion of gas particles, increasing the likelihood of particle capture.
To address the second objective, filtration membranes validated for bacterial retention are employed. These are also hydrophobic, helping to prevent gas humidification caused by condensation.
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