Calibration of Brookfield Viscometer in Pharmaceuticals

1. Introduction

A Brookfield viscometer is widely used in pharmaceutical industries to measure the viscosity of semi-solids, creams, gels, and certain liquid formulations.
Regular calibration ensures accuracy, reproducibility, and compliance with GMP and pharmacopoeial requirements.

2. Objective

• To verify the accuracy of viscosity readings.

• To ensure instrument performance is within acceptable limits.

• To maintain traceability to certified standards.

3. Principle

Calibration involves comparing viscosity readings of certified viscosity standard fluids (traceable to NIST) with their known values at a controlled temperature.
If the observed values fall within the acceptable tolerance range specified by the manufacturer (usually ±1% for Brookfield), the viscometer is considered calibrated.

4. Equipment & Materials

• Brookfield viscometer (LV, RV, or appropriate model)

• Certified viscosity standard fluids (e.g., Brookfield Silicone Oil Standards)

• Temperature-controlled water bath

• Appropriate spindles for the instrument model

• Stopwatch (if needed for manual models)

5. Procedure

1. Preparation

   • Clean the spindle and sample chamber with a suitable solvent and dry completely.

   • Set the viscometer to the correct speed and spindle as per manufacturer’s instructions.

   • Maintain the test fluid at the specified calibration temperature (commonly 25 ± 0.1 °C).

2. Measurement

   • Immerse the spindle into the viscosity standard fluid up to the immersion groove.

   • Start the viscometer and allow readings to stabilize (as per instrument guidelines).

   • Record the viscosity reading.

3. Comparison

   • Compare the measured viscosity to the certified value of the standard at the same temperature.

   • Repeat for all required viscosity ranges using different standards.

4. Acceptance Criteria

   • Reading should be within ±1% of full-scale range (or as specified by the manufacturer).

   • If results are outside the limit, perform maintenance/servicing and recalibrate.

6. Calibration Frequency

• Before first use

• Annually (or as per SOP)

• After repairs, spindle replacement, or suspected malfunction

7. Documentation

• Viscometer ID and model

• Calibration date

• Standard fluid lot number and certified value

• Spindle number, speed, and temperature

• Observed viscosity and % deviation

• Pass/Fail status

• Signatures of analyst and reviewer

8. Regulatory References

• Brookfield Viscometer Operating Manual

• USP <912> Viscosity

• ISO 2555: Plastics — Resins in the Liquid State or as Emulsions or Dispersions — Determination of Apparent Viscosity Using a Rotational Viscometer