Filter media MCQs With Answer

Filter media MCQs With Answer is an essential resource for B. Pharm students preparing for exams and practicals in pharmaceutical filtration. This guide covers filter types (membrane, depth, HEPA, pleated), key properties (pore size, porosity, tortuosity, flux), filtration mechanisms (straining, adsorption, diffusion, cake formation), validation methods (bubble point, pressure-hold, bacterial challenge) and practical considerations (chemical compatibility, fouling, cleaning, filter aids). Clear, focused MCQs with answers help reinforce theory and practical decision-making in sterile filtration, clarification, and viral removal. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. What is the primary function of filter media in pharmaceutical manufacturing?

• To remove particulates and microorganisms from liquids and gases
• To change the pH of the solution
• To increase the temperature of the product
• To act as a preservative

Correct Answer: To remove particulates and microorganisms from liquids and gases

Q2. Which filter pore size is commonly used for sterile filtration of parenteral solutions?

• 0.22 µm membrane filters
• 0.8 µm depth filters
• 5 µm cartridge filters
• 1.2 µm sand filters

Correct Answer: 0.22 µm membrane filters

Q3. What distinguishes an absolute filter rating from a nominal rating?

• Absolute filters remove nearly all particles of a specified size; nominal filters remove a proportion of such particles
• Nominal filters remove nearly all particles; absolute filters remove a proportion
• Absolute filters are always made of metal; nominal are polymeric
• Nominal filters are used only for air, absolute only for liquids

Correct Answer: Absolute filters remove nearly all particles of a specified size; nominal filters remove a proportion of such particles

Q4. Which capture mechanism predominates for very small particles much smaller than the membrane pore size?

• Diffusion (Brownian motion)
• Sieving/straining
• Inertial impaction
• Gravity settling

Correct Answer: Diffusion (Brownian motion)

Q5. What does a successful bubble point test indicate about a membrane filter?

• Filter integrity and maximum pore connectivity (no large defects)
• Chemical compatibility with solvents
• Mechanical tensile strength
• Microbial growth on the membrane

Correct Answer: Filter integrity and maximum pore connectivity (no large defects)

Q6. Which material is commonly used for depth filter media in pharmaceutical clarification?

• Cellulose fibers and filter aid matrix
• Thin PTFE membranes
• Glass microporous films only
• Ceramic ultrafiltration membranes exclusively

Correct Answer: Cellulose fibers and filter aid matrix

Q7. Which of the following is NOT a membrane filter material?

• Diatomaceous earth (filter aid)
• Cellulose acetate
• Polyethersulfone (PES)
• Polytetrafluoroethylene (PTFE)

Correct Answer: Diatomaceous earth (filter aid)

Q8. HEPA filters used in cleanrooms are typically rated to remove what fraction of 0.3 µm particles?

• 99.97%
• 50%
• 90%
• 10%

Correct Answer: 99.97%

Q9. Which integrity test is commonly used after sterilizing filtration to confirm the membrane remains intact?

• Bubble point test
• pH test of filtrate
• Colorimetric assay
• Thermal gravimetric analysis

Correct Answer: Bubble point test

Q10. What type of filtration is characterized by cake formation on the surface and subsequent cake resistance?

• Cake filtration (surface filtration)
• Depth filtration
• Membrane adsorption
• Crossflow ultrafiltration

Correct Answer: Cake filtration (surface filtration)

Q11. Darcy’s law in filtration relates which of the following?

• Fluid flux to pressure drop, viscosity, and permeability
• pH to solubility
• Temperature to membrane pore size
• Conductivity to particle count

Correct Answer: Fluid flux to pressure drop, viscosity, and permeability

Q12. What is the typical pore size range for microfiltration membranes?

• 0.1–10 µm
• 1–10 nm
• 0.001–0.1 µm
• 100–1000 µm

Correct Answer: 0.1–10 µm

Q13. Ultrafiltration membrane performance is commonly specified by which parameter?

• Molecular weight cutoff (MWCO)
• Pore diameter in µm only
• Electrical conductivity
• Glass transition temperature

Correct Answer: Molecular weight cutoff (MWCO)

Q14. What is the principal role of activated carbon as a filter medium?

• Adsorption of organic impurities, odor, and color
• Sterilization by pore removal of bacteria
• Mechanical removal of large particulates above 50 µm
• Providing structural support only

Correct Answer: Adsorption of organic impurities, odor, and color

Q15. In filtration terminology, what does ‘fouling’ refer to?

• Deposition of solids or macromolecules on/in filter causing flux decline
• Intentional coating to improve retention
• Sterilization of the membrane during use
• Cleaning the filter with solvent

Correct Answer: Deposition of solids or macromolecules on/in filter causing flux decline

Q16. Backwashing is an effective cleaning method for which type of filtration system?

• Sand and depth filter beds
• Disposable 0.22 µm membrane cartridges only
• Activated carbon in sealed cartridges that cannot be drained
• Pleated hospital HEPA housings

Correct Answer: Sand and depth filter beds

Q17. Which validation test demonstrates that a sterilizing-grade filter can retain bacteria?

• Bacterial challenge (bacterial retention) test
• Viscosity measurement
• pH stability test
• Color comparison test

Correct Answer: Bacterial challenge (bacterial retention) test

Q18. Filterability of a pharmaceutical solution is commonly assessed by measuring which of the following?

• Turbidity and particulate count
• Color only
• Osmolality alone
• Surface tension exclusively

Correct Answer: Turbidity and particulate count

Q19. Which membrane material is hydrophobic and often used for gas filtration and venting?

• PTFE (polytetrafluoroethylene)
• Cellulose acetate
• Polyethersulfone (PES)
• Hydrophilic nylon

Correct Answer: PTFE (polytetrafluoroethylene)

Q20. What is the main advantage of pleated cartridge filters compared to flat sheet elements?

• Increased surface area within the same housing volume
• Reduced chemical compatibility
• Lower mechanical strength
• Smaller overall area for filtration

Correct Answer: Increased surface area within the same housing volume

Q21. What does the ‘mean pore size’ of a filter describe?

• The average pore diameter within a distribution of pores
• The largest pore present only
• The smallest pore present only
• The total number of pores per cm2

Correct Answer: The average pore diameter within a distribution of pores

Q22. Which sterilization method can damage some polymeric membrane filters if not validated?

• Autoclaving (steam sterilization at high temperature and pressure)
• Using filtered air only
• Room-temperature UV exposure for 1 minute
• Drying under vacuum at ambient temperature

Correct Answer: Autoclaving (steam sterilization at high temperature and pressure)

Q23. During filtration, cake formation typically causes which change in system performance?

• An increase in differential pressure across the filter
• A decrease in solution viscosity
• A reduction in particle concentration upstream
• An immediate decrease in solute concentration downstream

Correct Answer: An increase in differential pressure across the filter

Q24. Which filter aid is commonly used to improve filtration of fine suspensions in the pharmaceutical industry?

• Diatomaceous earth (DE)
• Polyvinyl chloride powder
• Calcium carbonate blocks
• Granular activated aluminum

Correct Answer: Diatomaceous earth (DE)

Q25. If feed viscosity increases, how is the required filter area affected for the same production rate?

• Required filter area increases
• Required filter area decreases
• Required filter area remains unchanged
• Viscosity does not affect filter area

Correct Answer: Required filter area increases

Q26. Which filtration technique is typically used for virus removal from biological fluids?

• Nanofiltration (virus filtration)
• Standard 5 µm depth filtration
• Sand filtration
• Carbon adsorption only

Correct Answer: Nanofiltration (virus filtration)

Q27. What does LRV stand for in viral clearance studies?

• Log Reduction Value
• Linear Retention Variable
• Liquid Removal Volume
• Lowest Residual Viability

Correct Answer: Log Reduction Value

Q28. Which analytical method is commonly used to measure particle retention efficiency of filters?

• Laser particle counting
• Thin-layer chromatography
• Flame photometry
• Refractive index only

Correct Answer: Laser particle counting

Q29. A 0.45 µm membrane filter is typically used for which purpose in pharma processing?

• Clarification and bioburden control prior to sterile filtration
• Final sterilizing filtration for injectables
• Removing viruses from plasma
• Air filtration in cleanrooms

Correct Answer: Clarification and bioburden control prior to sterile filtration

Q30. For sterilizing a heat-sensitive protein solution, which filter selection is most appropriate?

• 0.22 µm sterilizing-grade membrane filter
• 5 µm depth filter
• Granular activated carbon bed
• 0.8 µm coarse cartridge

Correct Answer: 0.22 µm sterilizing-grade membrane filter

Q31. How is a ‘nominal’ pore size best described?

• An approximate size where a majority of particles are retained but not guaranteed
• An exact maximum pore diameter guaranteed by the manufacturer
• Only applicable to HEPA filters
• A measure of membrane thickness

Correct Answer: An approximate size where a majority of particles are retained but not guaranteed

Q32. What is the effect of turbulent flow near a membrane surface on fouling?

• It can reduce fouling by scouring the membrane surface
• It always increases fouling
• It has no impact on fouling
• It dissolves the membrane material

Correct Answer: It can reduce fouling by scouring the membrane surface

Q33. Which surface property of a filter media strongly affects protein adsorption?

• Hydrophobicity (surface hydrophobic character)
• Electrical conductivity
• Magnetic susceptibility
• Radioactivity

Correct Answer: Hydrophobicity (surface hydrophobic character)

Q34. Which method is commonly used to test HEPA filter integrity in cleanrooms?

• Aerosol challenge test (e.g., DOP/PAO) with photometer
• pH strip test
• Visual color inspection only
• Mass spectrometry for trace metals

Correct Answer: Aerosol challenge test (e.g., DOP/PAO) with photometer

Q35. What is the primary mechanism of particle removal in depth filtration?

• Entrapment within the porous filter matrix
• Complete surface cake formation only
• Evaporation of the carrier fluid
• Chemical reaction with the filter material

Correct Answer: Entrapment within the porous filter matrix

Q36. Which membrane material is often preferred for low protein-binding applications?

• Polyethersulfone (PES)
• Cellulose nitrate (high-binding)
• Raw PTFE without treatment (hydrophobic high-binding)
• Aluminum foil

Correct Answer: Polyethersulfone (PES)

Q37. What type of membrane is commonly used for vent filters on sterile vessels and autoclave ports?

• 0.22 µm hydrophobic membrane vents
• 5 µm hydrophilic membrane vents
• HEPA liquid filters
• Granular carbon vents

Correct Answer: 0.22 µm hydrophobic membrane vents

Q38. Filter flux is most correctly defined as which of the following?

• Flow rate per unit membrane area (e.g., L/m2·h)
• Total flow rate only (L/min)
• Pressure drop across the system only
• Concentration of particles in feed

Correct Answer: Flow rate per unit membrane area (e.g., L/m2·h)

Q39. Which strategy reduces microbial contamination risk during sterile filtration?

• Use a prefilter (e.g., 0.45 µm) followed by a 0.22 µm sterilizing-grade filter
• Filter only through a single coarse cartridge
• Bypass the filter when flow is slow
• Use only activated carbon without a membrane filter

Correct Answer: Use a prefilter (e.g., 0.45 µm) followed by a 0.22 µm sterilizing-grade filter

Q40. What is the main function of a prefilter upstream of a sterilizing membrane?

• Remove larger particles to protect and extend life of final membrane
• Adjust pH of feed
• Increase the temperature of feed
• Sterilize the solution by itself

Correct Answer: Remove larger particles to protect and extend life of final membrane

Q41. Which integrity test measures pressure decay to detect leaks in a filter assembly?

• Pressure hold (pressure decay) test
• UV absorbance test
• Mass balance test
• Visual dye penetration only

Correct Answer: Pressure hold (pressure decay) test

Q42. Which cleaning agent is commonly used to remove organic/protein fouling from filters?

• Sodium hydroxide (alkaline cleaning)
• Pure water only
• Neutral oil lubricants
• Hydrochloric acid for proteins

Correct Answer: Sodium hydroxide (alkaline cleaning)

Q43. Which of the following is NOT a benefit of pleating a filter element?

• Reduces the intrinsic pore size of the filter material
• Increases effective surface area
• Lowers pressure drop for a given flow
• Allows compact housing design with more media

Correct Answer: Reduces the intrinsic pore size of the filter material

Q44. Which filter media is least resistant to strong oxidizing agents?

• Cellulose-based filter media
• PTFE membrane
• Glass fiber
• Stainless steel sintered element

Correct Answer: Cellulose-based filter media

Q45. Which technique is effective for removing endotoxin (lipopolysaccharide) from an aqueous pharmaceutical solution?

• Ultrafiltration or specialized endotoxin-removal/adsorptive membranes
• Standard 0.45 µm filtration only
• HEPA air filtration
• Simple gravity settling

Correct Answer: Ultrafiltration or specialized endotoxin-removal/adsorptive membranes

Q46. What is the definition of ‘critical flux’ in membrane filtration?

• The flux below which fouling does not increase (negligible fouling)
• The maximum pressure a membrane can withstand
• The flux at which the membrane dissolves
• The time to first visible cake formation

Correct Answer: The flux below which fouling does not increase (negligible fouling)

Q47. Which material is commonly used for filter housings handling corrosive pharmaceutical solutions?

• Stainless steel (e.g., 316L)
• Untreated carbon steel
• Pure copper shells
• Wooden enclosures

Correct Answer: Stainless steel (e.g., 316L)

Q48. Viral removal by filtration typically uses nanofiltration membranes with approximate pore sizes in which range?

• ~15–50 nm (nanofiltration)
• 0.5–5 µm
• 0.1–1 mm
• 100–200 nm only

Correct Answer: ~15–50 nm (nanofiltration)

Q49. Which term describes the complexity or winding path that fluid takes through a porous filter media?

• Tortuosity
• Porosity only
• Pore pressure
• Hydrophobicity

Correct Answer: Tortuosity

Q50. Why is it important to sterilize and maintain cleanliness of filter housings and connections in aseptic processing?

• To prevent recontamination and maintain aseptic conditions during filtration
• To increase pore size of the filter
• To change the chemical composition of the media
• To add nutrients for microbial growth

Correct Answer: To prevent recontamination and maintain aseptic conditions during filtration

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com