Question 1

What are the USP apparatus types used in dissolution testing?

Accepted Answer

USP defines several dissolution apparatus types. Apparatus 1 (Basket) and Apparatus 2 (Paddle) are the most commonly used for solid oral dosage forms. Apparatus 3 (Reciprocating Cylinder), Apparatus 4 (Flow-Through Cell), Apparatus 5 (Paddle Over Disk), Apparatus 6 (Cylinder), and Apparatus 7 (Reciprocating Holder) are used for specialized applications.

Question 2

How often should dissolution equipment be calibrated?

Accepted Answer

Dissolution equipment should be calibrated at a minimum annually, or whenever the instrument is moved, repaired, or when results are suspect. Many laboratories perform calibration semi-annually or quarterly depending on their quality system requirements and regulatory guidance.

Question 3

What is the difference between calibration and performance verification?

Accepted Answer

Calibration involves adjusting or confirming that an instrument measures within specified tolerances using traceable reference standards. Performance verification (PV) confirms the instrument performs as expected under defined conditions — for dissolution, this typically involves running USP Prednisone or Salicylic Acid tablets and confirming results fall within acceptance criteria.

Question 4

What are the mechanical calibration parameters for a dissolution tester?

Accepted Answer

Key mechanical calibration parameters include: vessel centering, vessel wobble, shaft wobble, paddle/basket height, rotation speed (RPM), temperature accuracy and uniformity, and vibration. All parameters must meet USP <711> tolerances.

Question 5

What causes high variability in dissolution results?

Accepted Answer

High variability can result from several sources: coning (tablet settling under the paddle), air bubbles on the dosage form, improper vessel centering, shaft wobble exceeding tolerance, temperature non-uniformity, sampling technique inconsistencies, or issues with the dosage form itself. Systematic troubleshooting should address mechanical parameters first before investigating formulation factors.

Question 6

How do I address coning in Apparatus 2 (Paddle) dissolution?

Accepted Answer

Coning occurs when undissolved particles accumulate in a cone shape beneath the paddle. Mitigation strategies include increasing paddle speed, using sinkers to keep the dosage form in the dissolution medium, switching to Apparatus 1 (Basket), or evaluating whether the paddle height is set correctly at 25 mm ± 2 mm from the vessel bottom.

Question 7

How should dissolution vessels be cleaned and maintained?

Accepted Answer

Dissolution vessels should be cleaned after each use with appropriate solvents and inspected for scratches, chips, or residue. Vessels should be inspected for volume accuracy periodically. Scratched or damaged vessels should be replaced, as surface irregularities can affect hydrodynamics and dissolution results.

Question 8

When should dissolution paddles and baskets be replaced?

Accepted Answer

Paddles and baskets should be inspected before each use for corrosion, deformation, or damage. Replace immediately if bent, corroded, or if the mesh on a basket is damaged. Even minor deformation can affect shaft wobble and hydrodynamics. Keep a log of usage and replace proactively based on your laboratory's preventive maintenance schedule.

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