Understanding the factors influencing filtration MCQs with answer is essential for B.Pharm students preparing for exams and practical labs. This concise introduction explains key filtration factors—transmembrane pressure, membrane pore size, fluid viscosity, temperature, particle size, cake formation, fouling mechanisms, and filter media selection—that determine filtration efficiency, flux, and product sterility. Emphasis on membrane filtration, depth filters, filter aids (e.g., diatomaceous earth), Darcy’s law, and integrity/validation tests prepares students for formulation, sterile processing, and quality control. SEO-rich keywords like filtration factors, membrane pore size, filter fouling, transmembrane pressure, and sterilizing filtration are integrated to boost relevance for pharmacy curricula. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which parameter most directly drives solvent flow through a membrane during pressure-driven filtration?
- Membrane pore size
- Transmembrane pressure
- Particle size
- Filter aid concentration
Correct Answer: Transmembrane pressure
Q2. In Darcy’s law for filtration J = ΔP / μR, what does μ represent?
- Membrane pore size
- Viscosity of the fluid
- Transmembrane pressure
- Filter resistance
Correct Answer: Viscosity of the fluid
Q3. Which is the primary effect of increasing fluid temperature on filtration rate, assuming other factors constant?
- Increase viscosity and reduce flux
- Decrease viscosity and increase flux
- Increase pore size of membrane
- No change in filtration rate
Correct Answer: Decrease viscosity and increase flux
Q4. What is the typical pore size used for sterilizing-grade membrane filters in pharmaceutical sterilizing filtration?
- 0.45 μm
- 0.22 μm
- 1.2 μm
- 10 μm
Correct Answer: 0.22 μm
Q5. Which fouling mechanism creates a layer of retained material on the upstream surface of the filter?
- Pore blocking
- Gel polarization
- Cake formation
- Shear thinning
Correct Answer: Cake formation
Q6. Which filter type is characterized by depth and tortuous pathways capturing particles throughout the medium?
- Membrane (surface) filter
- Depth filter
- Centrifugal filter
- Crossflow membrane
Correct Answer: Depth filter
Q7. Cross-flow filtration primarily reduces which problem compared with dead-end filtration?
- Membrane chemical compatibility
- Transmembrane pressure variability
- Cake buildup and rapid flux decline
- Pore size distribution
Correct Answer: Cake buildup and rapid flux decline
Q8. Which factor determines whether a particle will be retained by a given membrane filter?
- Pore size relative to particle size
- Operating room humidity
- Filter color
- Filter packaging type
Correct Answer: Pore size relative to particle size
Q9. What is the effect of increasing feed flow velocity in cross-flow filtration on concentration polarization?
- Increases polarization
- Decreases polarization
- No effect on polarization
- Destroys membrane pores
Correct Answer: Decreases polarization
Q10. Which pharmaceutical practice commonly requires filter integrity testing after sterilizing filtration?
- Tablet coating
- Parenteral sterile solution production
- Granulation drying
- Capsule filling
Correct Answer: Parenteral sterile solution production
Q11. The resistance-in-series model expresses total resistance as membrane resistance plus cake resistance. Which operating change primarily reduces cake resistance?
- Reducing feed concentration
- Using a thicker membrane
- Reducing transmembrane pressure
- Increasing membrane pore size beyond particle size
Correct Answer: Reducing feed concentration
Q12. Which of the following is a common filter aid used to improve filtration rate and clarity?
- Sodium chloride
- Diatomaceous earth (celite)
- Sucrose
- Magnesium stearate
Correct Answer: Diatomaceous earth (celite)
Q13. For membrane filtration, what does MWCO (molecular weight cut-off) describe?
- Pore size in micrometers
- Molecular weight at which 90% of solute is retained
- Maximum working pressure
- Membrane thickness
Correct Answer: Molecular weight at which 90% of solute is retained
Q14. Which integrity test assesses the largest pore size or defects in a sterilizing-grade membrane by measuring the pressure required to force air through a wetted filter?
- Bacterial challenge test
- Bubble point test
- Viscosity test
- Permeate conductivity test
Correct Answer: Bubble point test
Q15. Which parameter will most likely increase fouling by adsorption of proteins to the membrane surface?
- Low protein concentration
- High ionic strength and protein affinity for membrane material
- High flow shear stress only
- Using a larger pore-size membrane
Correct Answer: High ionic strength and protein affinity for membrane material
Q16. During filtration, what is concentration polarization?
- Accumulation of retained solute near the membrane surface
- Even distribution of particles in feed
- Membrane swelling in solvent
- Instantaneous membrane failure
Correct Answer: Accumulation of retained solute near the membrane surface
Q17. Which operational change can help control concentration polarization in membrane processes?
- Lowering cross-flow velocity
- Increasing cross-flow velocity
- Eliminating transmembrane pressure
- Decreasing feed temperature drastically
Correct Answer: Increasing cross-flow velocity
Q18. What is the likely result of using a filter pore size that is larger than the majority of particles in suspension?
- Improved retention and sterility
- Poor retention and possible product contamination
- Increased cake formation only
- Membrane integrity improvement
Correct Answer: Poor retention and possible product contamination
Q19. In depth filtration using filter aids, what is the purpose of pre-coating?
- To increase membrane pore size
- To form a cake layer that protects the filter and improves clarity
- To sterilize the feed stream
- To dissolve particulates
Correct Answer: To form a cake layer that protects the filter and improves clarity
Q20. Which factor does NOT directly affect filtration flux according to resistance models?
- Feed viscosity
- Membrane resistance
- Color of the feed vessel
- Transmembrane pressure
Correct Answer: Color of the feed vessel
Q21. What is the primary advantage of sterilizing filtration over heat sterilization for heat-labile drugs?
- Lower operational cost always
- Preserves drug stability by avoiding heat exposure
- Produces larger particle sizes
- Removes all dissolved ions
Correct Answer: Preserves drug stability by avoiding heat exposure
Q22. Which term describes the pressure difference across the membrane in filtration?
- Hydraulic head
- Transmembrane pressure (TMP)
- Osmotic pressure only
- Capillary pressure
Correct Answer: Transmembrane pressure (TMP)
Q23. For colloidal suspensions, which interaction often influences filterability and fouling?
- Gravitational attraction
- Electrostatic (zeta potential) interactions
- Color attraction
- Optical refraction
Correct Answer: Electrostatic (zeta potential) interactions
Q24. Which cleaning strategy is commonly used to restore membrane performance after fouling?
- Backflushing and chemical cleaning
- Increasing feed concentration
- Reducing cross-flow velocity permanently
- Applying static pressure only
Correct Answer: Backflushing and chemical cleaning
Q25. Which filtration method is most appropriate for removing bacteria from a sterile parenteral solution while preserving active ingredients?
- Steam sterilization at 121°C
- 0.22 μm membrane filtration (sterile filtration)
- Microcentrifugation only
- Freeze-thaw cycles
Correct Answer: 0.22 μm membrane filtration (sterile filtration)
Q26. How does increasing feed solids concentration generally affect filtration performance?
- Improves flux and reduces cake formation
- Has no effect on flux
- Increases cake resistance and reduces flux
- Reduces membrane pore size permanently
Correct Answer: Increases cake resistance and reduces flux
Q27. Which property of a membrane is most directly related to its selectivity for macromolecules?
- Surface color
- Pore size distribution and MWCO
- Operating pressure only
- Membrane tensile strength
Correct Answer: Pore size distribution and MWCO
Q28. What is the likely outcome if transmembrane pressure is increased beyond optimal values in compressible cakes?
- Cake becomes more porous and flux rises
- Cake compresses, resistance increases, and flux may drop
- Membrane dissolves
- Particle size decreases
Correct Answer: Cake compresses, resistance increases, and flux may drop
Q29. Which analytical test directly demonstrates bacterial retention capability of a sterilizing filter?
- Bubble point test
- Bacterial challenge/retention test
- pH measurement
- Viscometry
Correct Answer: Bacterial challenge/retention test
Q30. Which membrane material is commonly used for aqueous pharmaceutical sterilizing filters due to low protein binding?
- Polypropylene
- Polytetrafluoroethylene (PTFE)
- Polyethersulfone (PES)
- Cellulose nitrate only
Correct Answer: Polyethersulfone (PES)
Q31. In dead-end filtration, what primarily causes faster flux decline compared to cross-flow?
- Lower feed concentration
- Pore enlargement
- Direct build-up of cake on filter surface
- Excessive cross-flow cleaning
Correct Answer: Direct build-up of cake on filter surface
Q32. Which phenomenon reduces observable permeate flux although membrane pores are not permanently blocked?
- Pore enlargement
- Concentration polarization
- Membrane mechanical fracture
- Permeate recirculation
Correct Answer: Concentration polarization
Q33. What factor should be checked for solvent compatibility with filter membranes?
- Membrane color code
- Solvent-membrane chemical compatibility chart and swelling behavior
- Membrane pore size only
- Feed viscosity only
Correct Answer: Solvent-membrane chemical compatibility chart and swelling behavior
Q34. Which of the following increases the likelihood of pore blocking rather than cake formation?
- Large particles much bigger than pore size
- Particles smaller than pores that enter and block pores
- Low feed concentration with high cross-flow
- Use of filter aid pre-coat
Correct Answer: Particles smaller than pores that enter and block pores
Q35. Which measurement is commonly used to monitor membrane performance over time in filtration processes?
- Permeate flux (flow per unit area)
- Membrane color change
- Feed tank volume only
- Ambient sound level
Correct Answer: Permeate flux (flow per unit area)
Q36. Which operational control helps minimize irreversible fouling of membranes in protein processing?
- Higher operating temperature that denatures proteins
- Optimized pH, frequent backflush, and appropriate cross-flow shear
- Maximizing TMP without cleaning
- Eliminating cross-flow altogether
Correct Answer: Optimized pH, frequent backflush, and appropriate cross-flow shear
Q37. What is the role of a filter housing design in pharmaceutical filtration?
- Only to hold the filter without affecting flow
- To ensure uniform flow distribution, minimize dead zones, and maintain sterility
- To increase the color of filtrate
- To change feed viscosity
Correct Answer: To ensure uniform flow distribution, minimize dead zones, and maintain sterility
Q38. Which of the following is a sign that a filter has reached end of life during a batch filtration?
- Permeate clarity improves
- Sharp decline in flux and rising differential pressure
- Bubble point increases above specification
- Membrane color turns transparent
Correct Answer: Sharp decline in flux and rising differential pressure
Q39. Which property of particles most strongly affects their ability to form a compressible cake?
- Particle color
- Particle compressibility and morphology (shape and deformability)
- Ambient light intensity
- Electrical wiring of equipment
Correct Answer: Particle compressibility and morphology (shape and deformability)
Q40. For viscous solutions, which approach can help increase filtration rate without changing membrane area?
- Decrease temperature to increase viscosity
- Increase temperature moderately to lower viscosity
- Use a smaller pore-size membrane
- Stop agitation entirely
Correct Answer: Increase temperature moderately to lower viscosity
Q41. What is the main advantage of using a graded porosity depth filter?
- Uniform pore size throughout the depth
- Progressive particle capture reduces surface blinding and increases capacity
- Only removes dissolved solutes
- Always sterilizes the product
Correct Answer: Progressive particle capture reduces surface blinding and increases capacity
Q42. Which factor is most important when selecting a membrane for organic solvent filtration?
- Membrane thickness only
- Chemical compatibility of membrane polymer with the solvent
- Color of the membrane housing
- Bubble point test value in water only
Correct Answer: Chemical compatibility of membrane polymer with the solvent
Q43. What does a declining bubble point value on a wetted filter typically indicate?
- Membrane pores are enlarging or integrity is compromised
- Perfect membrane integrity
- Feed viscosity has decreased
- Filter aid concentration increased
Correct Answer: Membrane pores are enlarging or integrity is compromised
Q44. Which practice reduces airborne contamination risk during sterile filtration transfers?
- Performing transfers in open air
- Using closed systems and aseptic connections under laminar flow or isolators
- Skipping filter integrity testing
- Warming product to high temperatures
Correct Answer: Using closed systems and aseptic connections under laminar flow or isolators
Q45. In membrane filtration, what does the term ‘flux decline’ refer to?
- Increase in permeate flow over time
- Decrease in permeate flow per unit membrane area over time
- Change in membrane color
- Instant rupture of membrane
Correct Answer: Decrease in permeate flow per unit membrane area over time
Q46. Which is a common method to evaluate filterability of a suspension in pharmaceutical development?
- Measuring filtration time or flux for a fixed volume under set pressure
- Measuring pH only
- Counting color units
- Estimating ambient humidity
Correct Answer: Measuring filtration time or flux for a fixed volume under set pressure
Q47. Why are hydrophilic membrane surfaces often preferred for aqueous sterile filtration?
- They repel water and block flow
- They wet easily, allowing consistent flow and reduced bubble formation
- They dissolve in aqueous media
- They increase protein adsorption dramatically
Correct Answer: They wet easily, allowing consistent flow and reduced bubble formation
Q48. Which of the following best describes a retention curve for a membrane?
- Plot of membrane color vs. time
- Fraction of particles retained versus particle size or molecular weight
- Plot of feed temperature only
- Graph of company sales
Correct Answer: Fraction of particles retained versus particle size or molecular weight
Q49. When filtering alcoholic solutions, which risk must be considered regarding membrane selection?
- Alcohol always increases flux regardless of membrane
- Chemical incompatibility and potential membrane swelling or degradation
- Alcohol sterilizes the membrane automatically
- Bubble point testing is unnecessary
Correct Answer: Chemical incompatibility and potential membrane swelling or degradation
Q50. Which combination of factors typically yields the highest initial permeate flux in a pressure-driven membrane process?
- Low TMP, high viscosity, small membrane area
- High TMP, low viscosity, large membrane area with minimal fouling
- High feed solids, compressible cake, low cross-flow
- Clogged pores and low transmembrane pressure
Correct Answer: High TMP, low viscosity, large membrane area with minimal fouling
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