Filtration in Pharmaceutical Processing PDF

Clarification and Filtration Dr.Hasanain Aljobori b.pharma,m.pharma 1  Definitions Clarification: a process that involves the removal or separation of a solid from a liquid, or a fluid from anoth...

Clarification and Filtration Dr.Hasanain Aljobori b.pharma,m.pharma 1  Definitions Clarification: a process that involves the removal or separation of a solid from a liquid, or a fluid from another fluid. The term “fluid” involves both liquids and gases. Clarification can be achieved using either filtration or centrifugation techniques. Filtration is mainly required to remove unwanted solid particles from a liquid product or air and Centrifugation is normally used to separate fluid from another fluid or to collect the solid as the product College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Definitions Filtration: the process in which particles are separated from a liquid by passing the liquid through a permeable material. Filtration The permeable medium is a porous material that separates particles from the liquid passing through it and it is Residue known as a filter. Thus, filtration is a unit operation in which a mixture of solids and liquid, the feed, suspension, dispersion, Filter influent, or slurry, is forced through a porous medium Filtrate (filter), where the solids are deposited or entrapped. The solids retained on a filter are known as the residue. The solids form a cake on the surface of the medium, College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester Application of Filtration in Pharmaceutical Processing Clarification of products to improve their appearance, i.e. to give them “sparkle” or “brightness”. Removal of potential irritants, e.g. from eye- drop preparation or solution applied to mucous membranes. Recovery of desired solid material from a suspension or slurry, e.g. to obtain a drug or excipient after a crystallization process. Production of water of appropriate quality or pharmaceutical uses such as Nanopure® water. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester Application of Filtration in Pharmaceutical Processing To meet the sterility specification (removal of microorganisms) required for some products using sterile filtration or aseptic filtration Sterilization of solution and vehicle of suspension that are chemically or physically unstable under heating conditions. Detection of microorganisms present in liquids by analyzing a suitable filter on which the bacteria are retained. To assess the efficiency of preservatives added to the pharmaceutical product. Recently, techniques such as nanofiltration, ultrafiltration, and microfiltration have been used to recover colloidal delivery systems from mother liquor. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Mechanisms of Filtration Four different mechanisms of filtration according to how the suspended material is trapped by the filter medium: Surface straining/ sieving: any particle that is larger than the pores of the medium deposits on the surface, and stays there until it is removed. Particles that are smaller in size than the pores pass quickly through the medium. Filtration occurs on the surface of the filter so-called membrane filter. Because filtration occurs on the surface, there is a tendency for them to become blocked unless the filter is carefully designed. Used where the contaminant level is low or small volumes need to be filtered. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Mechanisms of Filtration Depth straining: Similar to the previous mechanism in which it is governed by the particle size or shape. However, the filter medium here is thick in comparison with the pore diameter particles will travel along the pore until they reach a point where the pore narrows down to a size too small for the particle to go any further so they become trapped. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Mechanisms of Filtration Depth filtration (impingement): The particles become entrapped in the depth of the medium, even though they are smaller in diameter, and possibly much smaller than the pore at that point. They become attached to the pore wall, or to another particle already held through van der Waals and other surface forces (entanglement). College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Mechanisms of Filtration Cake Filtration (auto filtration): Cake filtration (which is a development of surface filtration) begins with the formation of a layer of particles on the surface of the filter medium, with larger pores bridged by a group of smaller particles. On this layer, a cake of particles accumulates to act as the filter medium for subsequent filtration. Cake filtration in which solid recovery is the goal. These definitions emphasize that the mechanisms of filtration may result in the trapping of far smaller particles than might be expected from the size of the pores in the medium. The actual mechanism or combination of mechanisms in any specific instance is dependent on the characteristics of both the medium and the suspension being filtered. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Filtration Equipment Equipment can be classified according to: The end product desired (filtrate or cake solids). Method of operation (batch or continuous) Type of operation (non-sterile, sterile filtration, centrifugation filtration) The driving force (gravity, vacuum, pressure, and centrifugation). This is the most important classification. 10 College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester  Filter Selection Once the purpose of the process has been determined, the selection of the filter medium can be made. For example: for sterilizing filtration (purpose), a 0.2 µm pore size is used; for clarification (purpose), a plate and frame filter or woven-fiber filter may be used. In general, a pore size smaller than the smallest particle to be removed is selected. The filter medium should be compatible with the liquid or gas to be filtered. It is advisable to check the chemical compatibility charts provided by the vendors for the selection of filter type. Filtration surface area is calculated after the filter media, pore size, required flow rate, and pressure differentials are established. College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester 11  Filter Selection For a liquid having a viscosity significantly different from that of water (1 cp), the clean water flow rate is divided by the viscosity of the liquid in centipoises to obtain the approximate initial flow rate for the liquid in question. The broad span of pharmaceutical requirements cannot be met by a single type of filter. The industrial pharmacist must achieve a balance between 1- filter media and 2- equipment capabilities, 3- slurry characteristics, and 4- quality specifications for the final product. The choice is usually a batch pressure filter, which uses either surface or depth filtration principles. 12 College of Pharmacy- Industrial Pharmacy I - 4th stage- Second Semester