Standard Operating Procedure for Rheological Evaluation of Gel Formulations
| Department | Gel Manufacturing |
|---|---|
| SOP No. | SOP/GM/067/2025 |
| Supersedes | SOP/GM/067/2022 |
| Page No. | Page 1 of 12 |
| Issue Date | 02/06/2025 |
| Effective Date | 04/06/2025 |
| Review Date | 02/06/2026 |
1. Purpose
To outline the standardized methodology for evaluating the rheological properties of gel formulations, ensuring batch-to-batch consistency and performance attributes.
2. Scope
This SOP applies to the Quality Control Laboratory and R&D departments responsible for conducting rheological testing of in-process and finished gel formulations.
3. Responsibilities
- QC Analyst: Conduct
rheological testing and document data as per the method.
QC Supervisor: Review and approve test results.
QA Officer: Ensure SOP compliance and adherence to validation protocols.
4. Accountability
The Head of Quality Control is accountable for proper implementation and adherence to this SOP.
5. Procedure
5.1 Equipment
- Brookfield Viscometer or Equivalent Rheometer
- Temperature-controlled sample holder (if required)
- Calibrated stopwatch
- Disposable sample containers
5.2 Calibration and Verification
- Ensure that the viscometer/rheometer is calibrated as per the instrument SOP before testing.
- Verify spindle type and speed setting based on product rheological range.
- Document calibration log in equipment register.
5.3 Sample Preparation
- Collect representative samples (approx. 50 g) of gel from each batch.
- Ensure sample is homogeneous and free from air bubbles.
- If testing temperature-sensitive products, equilibrate to 25°C ± 2°C.
5.4 Test Parameters
- Viscosity Measurement: Measured in centipoise (cP) or Pa·s
- Thixotropy: Time-dependent shear thinning
- Yield Stress: Minimum stress required to initiate flow
- Flow Curve Analysis: Stress vs. shear rate profile
5.5 Test Execution
- Mount appropriate spindle and set speed (e.g., Spindle No. 6 at 10 RPM).
- Fill sample container up to indicated mark without disturbing gel structure.
- Start measurement and allow stabilization time of 30 seconds.
- Record viscosity values at predefined intervals (e.g., 10, 20, 30, 60 sec).
- Repeat at multiple speeds to determine thixotropic behavior if required.
5.6 Data Recording
All results should be entered into the Rheology Test Sheet (Annexure-1) along with sample details, instrument settings, and observations.
5.7 Acceptance Criteria
Compare results with specification limits as defined in the product specification file. Any deviation should be investigated and reported.
5.8 Precautions
- Do not reuse samples or spindles without proper cleaning.
- Ensure no entrapped air during filling as it affects reading accuracy.
6. Abbreviations
- SOP: Standard Operating Procedure
- QC: Quality Control
- RPM: Revolutions Per Minute
- cP: Centipoise
7. Documents
- Rheology Test Sheet – Annexure-1
- Viscometer Calibration Log – Annexure-2
8. References
- USP General Chapter 911 – Viscosity
- ICH Q6A Specifications Guidelines
- Instrument User Manual
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: Rheology Test Sheet
| Product Name | |
|---|---|
| Batch Number | |
| Date of Testing | |
| Spindle Used | |
| RPM | |
| Temperature | |
| Viscosity (cP) | |
| Thixotropy Observed | |
| Analyst Name/Sign |
Annexure-2: Viscometer Calibration Log
| Calibration Date | Standard Used | Expected Viscosity | Observed Viscosity | Status (Pass/Fail) | Remarks |
|---|---|---|---|---|---|
Revision History
| Revision Date | Revision No. | Details | Reason | Approved By |
|---|---|---|---|---|
| 08/05/2022 | 1.0 | Initial version | New SOP Release | QA Head |
| 02/06/2025 | 2.0 | Included new viscosity parameters | Periodic Review | QA Head |