Performance Qualification (PQ) of Weighing Balance in Pharma Industry
In the pharmaceutical industry, weighing balances play a critical role in ensuring accuracy and compliance during manufacturing and quality control processes. To maintain data integrity and regulatory compliance, balances must undergo qualification as per Good Manufacturing Practices (GMP). After IQ (Installation Qualification) and OQ (Operational Qualification), the final stage is PQ – Performance Qualification.
PQ verifies that the balance performs consistently and accurately under actual working conditions. Let’s explore how to perform PQ for a weighing balance.
What is Performance Qualification (PQ)?
Performance Qualification is the documented evidence that a weighing balance operates consistently and delivers accurate results during routine usage. PQ ensures that the balance is reliable not just in theory, but also in the real working environment.
Steps to Perform PQ for Weighing Balance
1. Preparation
Identify the balance (ID, model, capacity).
Ensure the environment is stable (no vibration, no air flow, proper temperature).
Use calibrated, certified standard weights (E2/F1 class as per balance resolution).
2. Repeatability Test
Place the same standard weight (e.g., 10 g) on the pan 10 times.
Record each reading.
Calculate the Standard Deviation (SD) and %RSD.
Acceptance: %RSD should meet balance specification (e.g., ≤0.1%).
3. Linearity Test
Use at least 5 different standard weights across the balance range (e.g., 10 g, 50 g, 100 g, 200 g).
Compare observed vs. actual values.
Acceptance: Deviation must be within ±0.1% or as per SOP.
4. Accuracy Test
Check low, medium, and high capacity weights.
Readings should be within acceptance tolerance.
5. Eccentricity (Corner Load) Test
Place a standard weight at the center and at four corners of the pan.
Variation between positions should not exceed defined limits.
Documentation
All results must be documented in the PQ report. Include:
Test method and procedure
Observed readings
Calculations (SD, %RSD, deviations)
Acceptance criteria comparison
Conclusion (Pass/Fail)
Example Acceptance Criteria
Repeatability: %RSD ≤ 0.1%
Linearity: Deviation within ±0.1%
Accuracy: ± tolerance per SOP
Eccentricity: Within manufacturer’s limits
Conclusion
Performance Qualification (PQ) of a weighing balance ensures the instrument is accurate, reliable, and compliant under routine conditions. It safeguards product quality, regulatory compliance, and patient safety. By performing PQ at defined intervals (e.g., annually) or after major maintenance, organizations can maintain confidence in their weighing processes.
👉 A well-documented PQ not only fulfills GMP requirements but also strengthens the company’s quality assurance system.