Coating technology and fluidized bed coating MCQs With Answer

Introduction: Coating Technology and Fluidized Bed Coating MCQs With Answer is designed for M.Pharm students preparing for advanced exams and practical applications in pharmaceutical manufacturing. This collection focuses on principles, equipment, process parameters, formulation components, common defects and troubleshooting methods specific to tablet and particle coating — with emphasis on fluidized bed techniques such as Wurster (bottom-spray), top-spray and tangential-spray systems. Questions cover polymer selection, plasticizers, solvents, spray physics, thermal balance, scale-up considerations, PAT tools, and safety/environmental aspects. Practicing these targeted MCQs will deepen conceptual understanding and improve problem-solving skills needed for designing robust coating processes and ensuring product quality.

Q1. What is the primary advantage of using a fluidized bed Wurster (bottom-spray) coater over a conventional pan coater for coating small particles?

• Better mixing of large tablets
• Uniform coating on small particles and pellets with controlled layer thickness
• Lower initial equipment cost
• Higher solvent retention in product

Correct Answer: Uniform coating on small particles and pellets with controlled layer thickness

Q2. Which parameter most directly controls droplet size during atomization in a spray coating process?

• Bed temperature
• Nozzle atomization pressure (or air pressure)
• Coating polymer molecular weight
• Tablet hardness

Correct Answer: Nozzle atomization pressure (or air pressure)

Q3. Which polymer is commonly used for enteric coating in aqueous systems for delayed release?

• Hydroxypropyl methylcellulose (HPMC)
• Methacrylic acid copolymer (Eudragit L/F type)
• Polyethylene glycol (PEG 4000)
• Povidone (PVP K30)

Correct Answer: Methacrylic acid copolymer (Eudragit L/F type)

Q4. During fluidized bed coating, which measured parameter best indicates whether the spray rate is appropriate relative to drying capacity?

• Drug assay of cores
• Inlet air temperature alone
• Product bed temperature (outlet or product temperature) and moisture content trend
• Particle size distribution

Correct Answer: Product bed temperature (outlet or product temperature) and moisture content trend

Q5. Which coating defect is characterized by formation of small craters and uneven surface texture often due to rapid solvent evaporation?

• Peeling
• Orange peel
• Bridging
• Pitting

Correct Answer: Orange peel

Q6. In a Wurster bottom-spray coater, what is the function of the draft tube?

• To increase spray pressure
• To provide a controlled upward air stream creating a core (wurzter) region for targeted coating
• To filter solvent vapors
• To reduce product temperature by cooling

Correct Answer: To provide a controlled upward air stream creating a core (wurzter) region for targeted coating

Q7. Which excipient is commonly used as a plasticizer in film coating formulations to improve film flexibility?

• Talc
• Triethyl citrate
• Calcium carbonate
• Microcrystalline cellulose

Correct Answer: Triethyl citrate

Q8. What is the main safety concern when using organic solvents in coating processes at manufacturing scale?

• Excessive tablet hardness
• Explosion and fire hazards due to flammable solvent vapors
• Increase in dissolution rate
• Decreased coating adhesion

Correct Answer: Explosion and fire hazards due to flammable solvent vapors

Q9. Which of the following best describes coating efficiency?

• Fraction of sprayed solids actually deposited on cores compared to total solids sprayed
• Time required to complete coating cycle
• Amount of solvent evaporated per hour
• Tablet friability after coating

Correct Answer: Fraction of sprayed solids actually deposited on cores compared to total solids sprayed

Q10. Which process analytical technology (PAT) tool is commonly used for in-line monitoring of coating uniformity and film thickness in fluidized bed coating?

• Near infrared spectroscopy (NIR)
• High-performance liquid chromatography (HPLC)
• Gas chromatography (GC)
• Optical microscopy off-line only

Correct Answer: Near infrared spectroscopy (NIR)

Q11. What is the likely cause of tablet coating peeling or lifting soon after application?

• Over-plasticization of the film
• Poor surface wetting due to inadequate binder or contamination on tablet surface
• Excessive atomization pressure producing fine droplets
• Using non-volatile plasticizers

Correct Answer: Poor surface wetting due to inadequate binder or contamination on tablet surface

Q12. In scale-up of fluidized bed coating, which dimensionless parameter helps to maintain similar fluidization regimes between lab and production scales?

• Reynolds number or superficial gas velocity normalized to particle terminal velocity (i.e., scaled fluidization number)
• Tablet hardness
• Viscosity in cP only
• Batch weight in kilograms

Correct Answer: Reynolds number or superficial gas velocity normalized to particle terminal velocity (i.e., scaled fluidization number)

Q13. For taste-masking of bitter API using fluidized bed coating on beads, which approach is most appropriate?

• Immediate release HPMC coating with no binder
• Multi-layer approach: drug-loaded core coated with a sustained or barrier polymer film (e.g., ethylcellulose) followed by functional coating
• Coating with pure pigment suspension
• Increase core porosity without coating

Correct Answer: Multi-layer approach: drug-loaded core coated with a sustained or barrier polymer film (e.g., ethylcellulose) followed by functional coating

Q14. Which operating change would most effectively reduce agglomeration during spray coating in a fluidized bed?

• Decrease atomization pressure to produce larger droplets
• Increase spray rate dramatically
• Lower inlet air temperature to allow slower drying
• Optimize spray rate and increase inlet air temperature to improve drying rate while keeping droplet size small

Correct Answer: Optimize spray rate and increase inlet air temperature to improve drying rate while keeping droplet size small

Q15. Which statement about solvent evaporation during coating is correct?

• Evaporation consumes no latent heat and does not affect product temperature
• Evaporation is endothermic, so excessive evaporation can cool the product bed and slow drying
• Evaporation is exothermic and always increases product temperature
• Evaporation rate is independent of inlet air humidity

Correct Answer: Evaporation is endothermic, so excessive evaporation can cool the product bed and slow drying

Q16. Which defect results when coating solution fills tablet tablet-to-tablet gaps and solidifies, causing tablets to stick together?

• Peeling
• Coning
• Picking and sticking (agglomeration)
• Orange peel

Correct Answer: Picking and sticking (agglomeration)

Q17. In polymer selection for controlled-release coating, which property of the polymer is most critical?

• UV absorbance spectrum
• Permeability to water and drug (rate-controlling characteristics)
• Melting point only
• Color of the polymer

Correct Answer: Permeability to water and drug (rate-controlling characteristics)

Q18. Which of the following is a common measure used to specify weight gain during coating?

• Coating viscosity in cP
• Percentage weight gain relative to core weight (e.g., 3% w/w)
• Spray nozzle orifice diameter in mm
• Inlet air temperature in °C

Correct Answer: Percentage weight gain relative to core weight (e.g., 3% w/w)

Q19. What is the principal reason for adding anti-tack agents such as talc to coating formulations?

• To act as a primary binder
• To reduce surface tackiness and prevent tablet-to-tablet sticking
• To increase spray density
• To raise the melting point of the film

Correct Answer: To reduce surface tackiness and prevent tablet-to-tablet sticking

Q20. In fluidized bed nozzle design, why is controlling droplet momentum important for coating quality?

• High droplet momentum always improves film smoothness regardless of other conditions
• Droplet momentum affects impact, spread and rebound on particles; inappropriate momentum causes poor adhesion, erosion or agglomeration
• Droplet momentum only affects color distribution
• Droplet momentum is irrelevant when using aqueous coatings

Correct Answer: Droplet momentum affects impact, spread and rebound on particles; inappropriate momentum causes poor adhesion, erosion or agglomeration

Download