Applications of filtration MCQs With Answer is an essential resource for B. Pharm students preparing for exams and practicals. This concise, keyword-rich introduction covers pharmaceutical filtration concepts, filter types, membrane sterilization, depth vs surface filtration, cake formation, filter aids, validation and integrity testing. It highlights applications such as product clarification, sterile filtration, concentrate recovery, and clarification of suspensions in drug manufacturing. Focused on pharmaceutical processes and regulatory expectations, these filtration MCQs help reinforce theory and practical decision-making in formulation and production. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. What is the primary mechanism of surface filtration used in membrane filters?
- Adsorption of solutes onto filter media surfaces
- Size exclusion where particles are retained on the membrane surface
- Chemical reaction between filter and particles
- Gravity settling within the filter pores
Correct Answer: Size exclusion where particles are retained on the membrane surface
Q2. Which pore size is commonly used for sterilizing-grade membrane filtration in sterile pharmaceutical processes?
- 10 µm
- 1.2 µm
- 0.45 µm
- 0.22 µm
Correct Answer: 0.22 µm
Q3. Which filtration type is most suitable for removing high loads of suspended solids prior to final polishing?
- Sterile membrane filtration
- Depth filtration using filter aids
- Nanofiltration
- Reverse osmosis
Correct Answer: Depth filtration using filter aids
Q4. Darcy’s law in filtration relates which of the following parameters?
- Filter pore size and microbial retention
- Pressure drop, fluid viscosity, flow rate, and cake resistance
- Temperature and chemical compatibility
- Filter area and membrane pore distribution
Correct Answer: Pressure drop, fluid viscosity, flow rate, and cake resistance
Q5. What is the primary purpose of using filter aids such as diatomaceous earth in pharmaceutical filtration?
- To chemically react with active ingredient
- To increase cake permeability and improve flow
- To sterilize the filtrate
- To reduce product solubility
Correct Answer: To increase cake permeability and improve flow
Q6. Which equipment is commonly used for continuous vacuum filtration of large-volume slurries in industry?
- Nutsche filter
- Rotary vacuum drum filter
- Plate and frame filter press
- Membrane ultrafiltration skid
Correct Answer: Rotary vacuum drum filter
Q7. What distinguishes depth filtration from surface filtration?
- Depth filtration uses membrane pores smaller than retained particles
- Depth filtration traps contaminants throughout a thick medium rather than only on the surface
- Surface filtration always uses activated carbon
- Surface filtration is only for gaseous streams
Correct Answer: Depth filtration traps contaminants throughout a thick medium rather than only on the surface
Q8. Which test is commonly used to verify integrity of hydrophobic or hydrophilic membrane filters after sterilizing filtration?
- pH test
- Bubble point or pressure-hold test
- Spectrophotometric assay
- Viscosity measurement
Correct Answer: Bubble point or pressure-hold test
Q9. In cake filtration, what effect does finer particle size have on cake resistance?
- Decreases cake resistance
- No effect on cake resistance
- Increases cake resistance due to smaller voids
- Transforms the cake into a membrane
Correct Answer: Increases cake resistance due to smaller voids
Q10. Which membrane process is most appropriate for concentration and desalting of macromolecules like proteins?
- Microfiltration
- Ultrafiltration
- Nanofiltration
- Reverse osmosis
Correct Answer: Ultrafiltration
Q11. What is the primary role of a prefilter or coarse filter in a pharmaceutical filtration train?
- To sterilize the product
- To reduce particle load and protect downstream fine filters
- To remove endotoxins selectively
- To adjust pH before final filtration
Correct Answer: To reduce particle load and protect downstream fine filters
Q12. Which of the following is a common filter aid used to improve clarification and prevent blinding?
- Polyethylene glycol
- Diatomaceous earth (kieselguhr)
- Sodium chloride
- Activated aluminum
Correct Answer: Diatomaceous earth (kieselguhr)
Q13. Which filtration parameter is most directly increased by increasing transmembrane pressure in membrane filtration (until fouling limits)?
- Permeate flux
- Membrane pore size
- Membrane thickness
- Product viscosity
Correct Answer: Permeate flux
Q14. What is the main advantage of tangential (crossflow) filtration compared to direct dead-end filtration?
- Lower initial cost always
- Reduced fouling by sweeping particles along the membrane surface
- Complete retention of all solutes regardless of size
- Does not require cleaning procedures
Correct Answer: Reduced fouling by sweeping particles along the membrane surface
Q15. Which filtration method is preferred for removing pyrogens (endotoxins) from water for injection?
- 0.22 µm sterile filtration alone
- Reverse osmosis followed by ultrafiltration and validated endotoxin removal
- Gravity filtration through cotton
- Activated carbon only
Correct Answer: Reverse osmosis followed by ultrafiltration and validated endotoxin removal
Q16. In the context of pharmaceutical filtration, what is “filter blinding”?
- When filter media becomes transparent under pressure
- When particles clog filter pores leading to reduced flow
- When filters remove only dissolved molecules
- When filters are sterilized improperly
Correct Answer: When particles clog filter pores leading to reduced flow
Q17. Which material is commonly used for sterile membrane filters due to chemical compatibility and low extractables?
- Cellulose acetate
- Glass fiber
- Polyvinylidene fluoride (PVDF)
- Metal mesh
Correct Answer: Polyvinylidene fluoride (PVDF)
Q18. What is a Nutsche filter primarily used for in pharmaceutical manufacturing?
- Continuous large-volume liquid clarification
- Batch filtration, cake washing and drying under controlled conditions
- Gas filtration in HVAC systems
- Membrane sterilization of final product
Correct Answer: Batch filtration, cake washing and drying under controlled conditions
Q19. Which of the following best describes “constant pressure” filtration?
- Pressure is fixed and flow rate declines as cake builds
- Flow rate is kept constant while pressure increases
- Both pressure and flow are kept constant
- Pressure decreases over time to maintain constant cake thickness
Correct Answer: Pressure is fixed and flow rate declines as cake builds
Q20. What is the purpose of a filterability test in process development?
- To measure chemical reactivity of filter materials
- To evaluate how easily a product stream can be filtered and predict equipment sizing
- To sterilize samples for microbiology
- To determine pH drift during filtration
Correct Answer: To evaluate how easily a product stream can be filtered and predict equipment sizing
Q21. Which filtration unit operation is best for concentrating macromolecules while allowing small salts to pass?
- Microfiltration
- Ultrafiltration
- Depth filtration
- Gravity filtration
Correct Answer: Ultrafiltration
Q22. Which factor does NOT directly influence cake resistance during filtration?
- Particle size distribution
- Compressibility of the cake
- Viscosity of the filtrate
- Color of the slurry
Correct Answer: Color of the slurry
Q23. What is “sterile filtration validation” expected to demonstrate?
- That the filter changes permeate chemistry
- That the filtration process consistently produces sterile product and filters perform as intended
- That filters are cheaper than autoclaving
- That no integrity testing is required post-filtration
Correct Answer: That the filtration process consistently produces sterile product and filters perform as intended
Q24. Which integrity test is more suitable for detecting gross defects in membrane filters at the end of filtration?
- pH measurement
- Bubble point test or pressure-hold test
- Conductivity measurement
- Thermogravimetric analysis
Correct Answer: Bubble point test or pressure-hold test
Q25. What is the usual objective of washing a cake on a Nutsche filter after filtration?
- To increase cake dryness by thermal conduction
- To remove mother liquor and impurities while retaining solids
- To sterilize the solids using solvents
- To dissolve the cake back into solution
Correct Answer: To remove mother liquor and impurities while retaining solids
Q26. Which of the following describes membrane fouling?
- Permanent chemical alteration of the membrane base material only
- Accumulation of particles, colloids or macromolecules on or within the membrane that reduces performance
- Increase in membrane pore size over time
- Complete dissolution of membrane into the permeate
Correct Answer: Accumulation of particles, colloids or macromolecules on or within the membrane that reduces performance
Q27. What is one regulatory expectation related to filtration in aseptic drug production?
- Filters need only be visually inspected
- Filter selection, validation, and routine integrity testing must be documented
- Filters may be reused indefinitely without records
- Bioburden control is not required if filters are 0.22 µm
Correct Answer: Filter selection, validation, and routine integrity testing must be documented
Q28. Which filtration process is effective for removing viruses from biological preparations?
- Microfiltration with 1–10 µm pores
- Ultrafiltration or virus-retentive nanofiltration specifically designed for virus removal
- Gravity filtration through cotton
- Activated carbon adsorption only
Correct Answer: Ultrafiltration or virus-retentive nanofiltration specifically designed for virus removal
Q29. How does cake washing efficiency depend on cake properties?
- Less dependent; washing always achieves 100% impurity removal
- Higher porosity and lower compressibility generally improve washing efficiency
- Only particle color matters for washing
- Washing efficiency is governed solely by wash solvent pH
Correct Answer: Higher porosity and lower compressibility generally improve washing efficiency
Q30. Which parameter is most important when selecting filter media for solvent filtration in API processing?
- Media color
- Chemical compatibility with the solvent and API
- Filter manufacturer’s logo
- Height of the filter housing
Correct Answer: Chemical compatibility with the solvent and API
Q31. What is the function of a sintered metal filter in pharmaceutical processes?
- To control pH of solutions
- To provide robust, cleanable filtration for gases and aggressive liquids at elevated temperatures
- To sterilize using gamma radiation
- To act as a primary sterile membrane for 0.22 µm retention
Correct Answer: To provide robust, cleanable filtration for gases and aggressive liquids at elevated temperatures
Q32. Which measure helps to reduce irreversible membrane fouling during a batch filtration run?
- Increasing feed temperature without limits
- Optimizing crossflow velocity and periodic backflushing or cleaning-in-place (CIP)
- Never cleaning the membrane to preserve sterility
- Using larger pore membranes for final sterile filtration
Correct Answer: Optimizing crossflow velocity and periodic backflushing or cleaning-in-place (CIP)
Q33. What is a key advantage of using a plate and frame filter press?
- Ideal for very low viscosity gases
- High solids recovery and ability to wash and dry cakes in batch operations
- Continuous self-cleaning operation without downtime
- Complete sterilization of filtrate by default
Correct Answer: High solids recovery and ability to wash and dry cakes in batch operations
Q34. Which test can be used to assess bacterial retention performance of a sterilizing filter during validation?
- Bubble point only
- Microbial challenge test using a defined microorganism (e.g., Brevundimonas diminuta)
- pH challenge test
- Spectral absorbance test
Correct Answer: Microbial challenge test using a defined microorganism (e.g., Brevundimonas diminuta)
Q35. For sterile filtration of protein solutions, which concern must be carefully managed?
- Protein adsorption to membrane reducing yield
- Increase in protein molecular weight during filtration
- Spontaneous generation of solvents
- Conversion of proteins to sugars
Correct Answer: Protein adsorption to membrane reducing yield
Q36. What is “cake compressibility” and why is it important?
- It is a measure of how easily the cake dissolves in solvent; irrelevant to filtration
- It describes how cake permeability decreases under pressure, affecting flow and washing
- It measures filter media tensile strength
- It is the color change of cake under light
Correct Answer: It describes how cake permeability decreases under pressure, affecting flow and washing
Q37. Which filtration method is most appropriate to remove submicron particles from process water?
- Gravity filtration through sand only
- Microfiltration using membrane filters
- Rotary vacuum filtration designed for solids
- Activated carbon polishing only
Correct Answer: Microfiltration using membrane filters
Q38. Why is extractables and leachables testing relevant for filter selection in pharmaceuticals?
- To ensure filters are colored correctly
- To verify that materials do not leach chemicals into the drug product that could affect safety or efficacy
- To confirm the filter will change the API structure intentionally
- To avoid the need for filter validation
Correct Answer: To verify that materials do not leach chemicals into the drug product that could affect safety or efficacy
Q39. In membrane filtration, what does “flux” refer to?
- The total volume retained by the membrane
- The volumetric flow rate of permeate per unit membrane area
- The electrical conductivity of the permeate
- The number of particles passing through per minute
Correct Answer: The volumetric flow rate of permeate per unit membrane area
Q40. Which practice is essential to maintain aseptic conditions during sterile filtration operations?
- Skipping prefilter steps to speed production
- Using validated sterile connectors, aseptic techniques, and in-process environmental control
- Opening final filter housings in non-controlled rooms
- Not performing integrity tests after production
Correct Answer: Using validated sterile connectors, aseptic techniques, and in-process environmental control
Q41. What is the typical application of nanofiltration in pharmaceutical water treatment?
- Sterile filtration of cell cultures
- Partial softening and removal of divalent ions and small organic molecules while allowing monovalent salts to pass partially
- Retention of viruses only
- Primary clarification of crude suspensions
Correct Answer: Partial softening and removal of divalent ions and small organic molecules while allowing monovalent salts to pass partially
Q42. How does temperature generally affect filtration viscosity and flux?
- Higher temperature increases viscosity and reduces flux
- Higher temperature decreases viscosity and can increase flux, but may affect stability
- Temperature has no effect on filtration
- Only freezing temperatures are relevant
Correct Answer: Higher temperature decreases viscosity and can increase flux, but may affect stability
Q43. What is a common indicator that a membrane filter has become fouled during a filtration run?
- Increase in permeate color without flux change
- Decline in permeate flux or increase in transmembrane pressure to maintain flux
- Decrease in feed viscosity only
- Instant sterilization of product
Correct Answer: Decline in permeate flux or increase in transmembrane pressure to maintain flux
Q44. Which cleaning strategy is commonly used for membrane systems to restore performance?
- Soaking in compatible chemical detergents followed by rinsing and sanitization (CIP)
- Always replacing the entire membrane after each batch
- Heating membranes to 300 °C
- Using only distilled water at ambient temperature without chemicals
Correct Answer: Soaking in compatible chemical detergents followed by rinsing and sanitization (CIP)
Q45. What role does filter housing design play in pharmaceutical filtration?
- Only aesthetics; it has no process impact
- Impacts flow distribution, cleaning ability, sterilization compatibility and material compatibility
- Allows filters to change pore size dynamically
- Makes filters replaceable without validation
Correct Answer: Impacts flow distribution, cleaning ability, sterilization compatibility and material compatibility
Q46. Which parameter is most crucial when scaling up a filtration process from lab to production?
- Brand of filter paper used in the lab
- Maintaining similar shear rates, fluxes, and cake characteristics to ensure comparable performance
- Color of the production vessel
- Replacing all membrane materials with metal sheets
Correct Answer: Maintaining similar shear rates, fluxes, and cake characteristics to ensure comparable performance
Q47. Why is bioburden control important before sterile filtration?
- Because sterile filters remove all chemical impurities
- Lowering bioburden reduces the microbial challenge to the filter and supports aseptic process control and product safety
- Bioburden does not matter if filter is 0.22 µm
- To increase the rate of fouling intentionally
Correct Answer: Lowering bioburden reduces the microbial challenge to the filter and supports aseptic process control and product safety
Q48. Which of the following is a key advantage of using single-use (disposable) filtration assemblies in biotech manufacturing?
- Unlimited reuse without validation
- Reduced cleaning and sterilization requirements and lower cross-contamination risk
- Always lower material costs long-term
- They remove the need for integrity testing
Correct Answer: Reduced cleaning and sterilization requirements and lower cross-contamination risk
Q49. What is the typical outcome when a filter cake is highly compressible under applied pressure?
- Permeability increases significantly
- Permeability decreases, leading to lower flow and potential process issues
- Cake becomes hydrophobic and floats
- Filter pore size increases automatically
Correct Answer: Permeability decreases, leading to lower flow and potential process issues
Q50. During sterile filtration, why is in-process temperature and pH monitoring important?
- They are irrelevant to filtration performance
- Temperature and pH can influence membrane performance, product stability, and microbial survival, so monitoring ensures consistent sterility and product quality
- To ensure the filter changes color
- Only temperature matters, pH never affects filtration
Correct Answer: Temperature and pH can influence membrane performance, product stability, and microbial survival, so monitoring ensures consistent sterility and product quality
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