a Brookfield viscometer.

2. Scope

This SOP applies to the Analytical Method Development (AMD) department responsible for determining the viscosity of pharmaceutical semi-solid products during product development, technology transfer, and stability studies.

3. Responsibilities

• Analytical Scientist: Develops the viscosity method and performs measurements using the appropriate spindle and speed.
• QC Analyst: Assists in equipment calibration, sample handling, and result verification.
• QA Executive: Reviews method validation data and ensures documentation compliance.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring that the viscosity method is validated, scientifically justified, and suitable for regulatory and commercial use.

5. Procedure

5.1 Instrument and Accessories

1. Brookfield Viscometer (DV-E, DV1, or equivalent)
2. Appropriate spindles (e.g., LV series for low viscosity or RV for high viscosity)
3. Temperature-controlled water bath (if required)
4. Standard viscosity calibration fluids

5.2 Instrument Calibration

1. Calibrate viscometer annually or as per manufacturer’s guidelines using certified viscosity standards.
2. Record calibration data in the instrument log (Annexure-2).

5.3 Sample Preparation

1. Ensure the sample is free from air bubbles and at specified temperature (e.g., 25 ± 0.5°C).
2. Use a wide-mouth beaker and fill to appropriate depth to cover the spindle immersion mark.
3. Allow the sample to equilibrate in a temperature-controlled environment for 15 minutes.

5.4 Method Development Parameters

1. Identify the appropriate spindle and speed to give full-scale torque between 10% and 90%.
2. Record spindle type, rotational speed (RPM), and time of measurement (usually 30–60 seconds).
3. If thixotropic behavior is observed, use continuous ramping or hysteresis loop profiling.

5.5 Viscosity Measurement

1. Assemble the viscometer and select spindle based on expected viscosity range.
2. Immerse spindle into the sample without trapping air bubbles.
3. Start rotation and allow reading to stabilize before recording.
4. Record readings in centipoise (cP) or mPa·s.

5.6 Acceptance Criteria

• RSD of triplicate readings ≤ 3%
• Viscosity within predefined specification range, e.g., 10,000–50,000 cP

5.7 Method Validation Parameters

1. Precision: Evaluate intra- and inter-day RSD (≤ 3%)
2. Ruggedness: Compare results between analysts, instruments, and batches
3. Robustness: Assess impact of slight variations in temperature, speed, and spindle

6. Abbreviations

• cP: Centipoise
• RPM: Revolutions Per Minute
• RSD: Relative Standard Deviation
• QA: Quality Assurance

7. Documents

1. Viscosity Measurement Log – Annexure-1
2. Calibration Record – Annexure-2
3. Method Validation Report – Annexure-3

8. References

• USP <912>: Viscosity
• Brookfield Engineering Operating Manual
• ICH Q2(R1): Validation of Analytical Procedures

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Ritika Mehra	Ajay Deshmukh	Sunita Reddy
Designation	Analytical Scientist	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Viscosity Measurement Log

Sample ID	Spindle	Speed (RPM)	Reading 1 (cP)	Reading 2 (cP)	Reading 3 (cP)	Average	Status
VIS-256-01	Spindle #4	10	25300	25120	25250	25223	Pass

Annexure-2: Calibration Record

Date	Instrument ID	Standard Used	Expected cP	Observed cP	Status
21/05/2025	BV-01	Brookfield Std. Fluid	12,000	11,850	Pass

Annexure-3: Method Validation Report

The viscosity method for gel-based product G-256 was validated across 3 days. RSD values were ≤ 1.8%, linearity across torque range was r = 0.998. Method found robust across spindle variations and temperature changes from 24–26°C.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Updated to include RSD criteria and spindle selection rationale	Annual SOP Review	Sunita Reddy
05/03/2022	1.0	Initial SOP Release	New SOP	QA Head