product release and development characterization.

3. Responsibilities

• QC Analysts: Perform rheological tests as per the defined protocol.
• QA Personnel: Verify results, review documentation, and ensure compliance with specifications.
• Formulation Scientists: Design rheological study methods and analyze data trends.

4. Accountability

Department Head – Gel Manufacturing and Head – Quality Control shall be accountable for implementation, review, and periodic training related to rheological evaluation procedures.

5. Procedure

5.1 Instrumentation and Calibration

1. Use a Brookfield Viscometer or Rheometer with appropriate spindles and temperature control system.
2. Ensure instrument calibration is within valid range using certified calibration fluids (Annexure-1).

5.2 Sample Preparation

1. Gently homogenize the gel sample using a sterile spatula to ensure uniformity before testing.
2. Fill the sample container without entrapping air bubbles.

5.3 Testing Conditions

1. Set the test temperature (e.g., 25°C ± 1°C) using the instrument’s temperature control.
2. Select the appropriate spindle (e.g., Spindle No. 64) and RPM as per the test protocol.

5.4 Parameters to Measure

1. Viscosity: Record in centipoise (cP) at various RPMs.
2. Flow Behavior: Assess thixotropy, pseudoplasticity, or Newtonian behavior.
3. Yield Stress: Use stress-controlled measurements if applicable.

5.5 Data Recording and Interpretation

1. Record time, temperature, RPM, spindle type, and viscosity in a Rheology Logbook (Annexure-2).
2. Plot flow curves to assess structural breakdown and recovery trends.
3. Compare with product specification range approved in the Master Formula Record (MFR).

5.6 Cleaning and Maintenance

1. Clean the spindle and sample holder with 70% IPA or a validated cleaning agent.
2. Log the cleaning details in the Instrument Usage Log (Annexure-3).

6. Abbreviations

• SOP: Standard Operating Procedure
• QC: Quality Control
• QA: Quality Assurance
• MFR: Master Formula Record

7. Documents

1. Rheological Instrument Calibration Record – Annexure-1
2. Rheology Test Logbook – Annexure-2
3. Instrument Cleaning and Maintenance Log – Annexure-3

8. References

• USP <1092> – The Rheological Properties of Semisolids
• ICH Q6A – Specifications: Test Procedures and Acceptance Criteria for New Drug Substances and Products

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation	Jr. Production Chemist	QA Executive	Head – Manufacturing
Department	Gel Manufacturing	Quality Assurance	Manufacturing

11. Annexures

Annexure-1: Rheological Instrument Calibration Record

Fluid Used	Expected Viscosity	Observed Viscosity	Status
Calibration Fluid A	1000 cP	995 cP	Pass

Annexure-2: Rheology Test Logbook

Date	Sample Code	Viscosity	Spindle	RPM	Remarks
01/06/2025	GLP-017	12500 cP	64	20	Within Spec

Annexure-3: Instrument Cleaning and Maintenance Log

Date	Cleaning Agent	Performed By	Remarks
01/06/2025	70% IPA	Technician A	Cleaned post-test

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
01/06/2022	1.0	Initial Issue	New SOP	QA Head
02/06/2025	2.0	Updated with flow behavior analysis	Annual Review	QA Head