Top 27+ Dissolution Test Interview Questions With Answers | USP & GMP Guide

Preparing for pharmaceutical interviews? Dissolution testing is one of the most frequently asked topics for QA, QC, Production, and Validation roles. This comprehensive guide covers USP dissolution apparatus, sink conditions, RPM, Q value, acceptance criteria, IVIVC, and method validation, all aligned with USP, ICH, and GMP expectations.

1. What Is a Dissolution Test in Pharmaceuticals?

Answer:
A dissolution test measures the rate and extent to which the active pharmaceutical ingredient (API) is released from a solid dosage form (tablet or capsule) into a dissolution medium under standardised conditions.

2. Why Is Dissolution Testing Important?

Answer:
Dissolution testing:

• Ensures batch-to-batch consistency
• Predicts drug bioavailability
• Acts as a critical quality attribute (CQA)
• Is mandatory for regulatory approval

3. What Apparatuses Are Used for Dissolution Testing?

Answer:
USP-recommended dissolution apparatus include:

• Apparatus 1: Basket
• Apparatus 2: Paddle
• Apparatus 3: Reciprocating Cylinder
• Apparatus 4: Flow-Through Cell
• Apparatus 5–7: Specialised applications

4. Which Is the Most Commonly Used Dissolution Apparatus?

Answer:

• USP Apparatus 2 (Paddle): Most common for tablets
• USP Apparatus 1 (Basket): Commonly used for capsules

5. What Is the Typical Dissolution Medium Volume?

Answer:
Generally, 500 mL to 1000 mL, with 900 mL being the most commonly used volume as per USP monographs.

6. What Are Sink Conditions in Dissolution Testing?

Answer:
Sink conditions exist when the dissolution medium volume is at least three times the volume required to form a saturated solution of the drug substance.

7. Factors Affecting Dissolution Rate

Answer:

• Drug surface area
• Agitation speed (RPM)
• Solubility of API
• pH and composition of medium
• Temperature
• Excipients

8. What Is the Standard Temperature for Dissolution Testing?

Answer:
37 ± 0.5°C, which simulates human physiological temperature.

9. How Are Samples Collected During Dissolution Testing?

Answer:
Samples are withdrawn at predefined time points, filtered, and analysed using UV spectrophotometry or HPLC.

10. What Is the Significance of RPM in Dissolution?

Answer:
RPM (revolutions per minute) controls the agitation speed, influencing hydrodynamic conditions and drug release rate.

11. What Is the Q Value in Dissolution Testing?

Answer:
The Q value is the specified percentage of the drug that must dissolve within a defined time (e.g., Q = 80% in 30 minutes).

12. How Is a Dissolution Medium Prepared?

Answer:
The medium (e.g., 0.1 N HCl, phosphate buffer) is:

• Prepared using purified water
• Adjusted to the required pH
• Degassed
• Equilibrated to 37°C

13. Why Is the Degassing of Dissolution Medium Important?

Answer:
Dissolved air can form bubbles on tablets or apparatus, causing poor reproducibility and inaccurate results.

14. Common Dissolution Media Used in Pharma

Answer:

• 0.1 N HCl
• Simulated Gastric Fluid (SGF)
• Simulated Intestinal Fluid (SIF)
• Phosphate buffer (pH 6.8 / 7.4)
• Purified water

15. Role of Surfactants in Dissolution Testing

Answer:
Surfactants such as Sodium Lauryl Sulfate (SLS) improve solubility of poorly soluble drugs, ensuring sink conditions.

16. What Is a Discriminatory Dissolution Method?

Answer:
A method sensitive enough to detect changes in formulation or manufacturing parameters that may affect in vivo drug performance.

17. Single-Point vs Multi-Point Dissolution Testing

Answer:

• Single-point: Drug release at one time (e.g., 30 min)
• Multi-point: Drug release profile over multiple time points

18. Calibration Requirements for Dissolution Apparatus

Answer:
Calibration is performed using USP Performance Verification Test (PVT) with calibrator tablets to ensure accuracy and precision.

19. Acceptance Criteria for Dissolution Testing

Answer (USP):

• Stage 1 (S1): 6 units ≥ Q + 5%
• Stage 2 (S2): 12 units, average ≥ Q, none < Q − 15%

20. How Are Dissolution Results Analysed?

Answer:
Percent drug release is plotted against time and compared with reference or innovator products.

21. Common Problems in Dissolution Testing

Answer:

• Coning
• Air bubble formation
• Incorrect RPM
• Non-sink conditions
• pH drift or evaporation

22. What Is Dissolution Profile Comparison (f2 Test)?

Answer:
An f2 similarity factor between 50 and 100 indicates comparable dissolution profiles, used for generic drug approval.

23. What Is IVIVC in Dissolution?

Answer:
IVIVC (In Vitro–In Vivo Correlation) links dissolution data with in vivo performance, supporting formulation development and biowaivers.

24. Difference Between Dissolution and Disintegration

Answer:

• Disintegration: Tablet breaks into particles
• Dissolution: API dissolves into the solution

25. How Is a Dissolution Method Validated?

Answer:
As per ICH guidelines, validation includes:

• Specificity
• Linearity
• Accuracy
• Precision
• Robustness
• Solution stability

26. What Are S1, S2, and S3 in Dissolution Testing?

Answer:

• S1: 6 units ≥ Q + 5%
• S2: 12 units; average ≥ Q; none < Q − 15%
• S3: 24 units; ≤ 2 units < Q − 15%, none < Q − 25%

27. Why is 900 mL of Media Commonly Used in Dissolution Tests?

Answer:
900 mL helps maintain sink conditions, minimises solubility variability, and better simulates in vivo dilution, producing consistent results.

28. What are “Q” and “Q + 5%” in Dissolution?

Answer:

• Q: Specified % of drug to be released
• Q + 5%: Stricter Stage-1 acceptance criterion
  Example: If Q = 80%, then Q + 5% = 85%

Conclusion

Dissolution testing is a critical quality control tool in the pharmaceutical industry. Mastering these dissolution test interview questions and answers will help you excel in QA, QC, Production, Validation, and regulatory interviews, while ensuring compliance with USP, ICH, FDA, and GMP standards.

Related:

Pharmaceutical Analysis

Further reading:

• Dissolution and Drug Release Tests