Calibration of Centrifuge Apparatus in Pharmaceuticals

1. Introduction

A centrifuge is used to separate substances of different densities under high-speed rotation. In pharmaceutical laboratories, it plays a critical role in sample preparation, microbial assays, plasma separation, and stability studies.
Calibration ensures that the centrifuge operates at accurate speed (RPM), relative centrifugal force (RCF), and timer settings, ensuring consistency and reliability in results.

2. Objective

• To verify the accuracy of centrifuge operational parameters.

• To comply with GMP, GLP, and pharmacopeial requirements.

• To ensure reliability in analytical and microbiological test results.

3. Parameters for Calibration

1. Rotor Speed (RPM) – checked using a tachometer.

2. Relative Centrifugal Force (RCF) – calculated from RPM and rotor radius.

   RCF=1.118×10−5×r×(RPM)2RCF = 1.118 \times 10^{-5} \times r \times (RPM)^2RCF=1.118×10−5×r×(RPM)2

   where r = rotor radius in cm.

3. Timer Accuracy – checked using a calibrated stopwatch.

4. Temperature (if refrigerated) – verified with a calibrated thermometer or temperature probe.

5. Imbalance detection (if applicable) – verified by loading uneven weights.

4. Equipment Required

• Calibrated digital tachometer (non-contact or contact type)

• Calibrated stopwatch

• Calibrated thermometer (for refrigerated centrifuges)

• Balance (for imbalance test)

• Manufacturer’s rotor radius specification

5. Calibration Procedure

A. Speed Verification

1. Run the centrifuge at the set RPM (e.g., 3000 RPM).

2. Use a tachometer to measure the actual rotor speed.

3. Record readings at various set speeds (low, medium, high).

4. Acceptable tolerance: ±5% or as per manufacturer/ISO guidelines.

B. Timer Verification

1. Set the centrifuge timer (e.g., 10 minutes).

2. Use a calibrated stopwatch to measure actual run time.

3. Tolerance: ±1% or as per SOP.

C. Temperature Verification (for refrigerated units)

1. Set desired temperature (e.g., 4°C).

2. Allow stabilization for at least 15 minutes.

3. Measure using a calibrated probe or thermometer.

4. Tolerance: ±2°C or as per manufacturer.

D. Imbalance Detection Check (if feature available)

1. Load uneven weights into opposite rotor positions.

2. Confirm automatic stop or imbalance alarm.

6. Calibration Frequency

• Initial: Before first use.

• Routine: Quarterly or as per SOP.

• After: Any repair or suspected malfunction.

7. Documentation

• Equipment ID, make, and model

• Date of calibration

• Measured vs. set values for RPM, time, and temperature

• % deviation and pass/fail status

• Analyst and reviewer signatures

8. References

• WHO Good Laboratory Practices

• USP <1058> Analytical Instrument Qualification

• Manufacturer’s operating manual

• ISO 13065 – Laboratory centrifuges — Methods for determination of performance

Example Statement

“The laboratory centrifuge (ID: CF-003) achieved 2995 RPM at a set speed of 3000 RPM (±0.17%), timer accuracy within ±0.5%, and temperature deviation within ±1.2°C. The unit meets GMP calibration requirements.”