Gel Manufacturing: SOP for In-Process Control of pH and Viscosity – V 2.0

Standard Operating Procedure for In-Process Control of pH and Viscosity in Gel Manufacturing

Department	Gel Manufacturing
SOP No.	SOP/GM/173/2025
Supersedes	SOP/GM/173/2022
Page No.	Page 1 of 8
Issue Date	09/06/2025
Effective Date	11/06/2025
Review Date	09/06/2027

1. Purpose

To outline the procedure for in-process control (IPC) of pH and viscosity during various stages of gel manufacturing to ensure compliance with predefined product specifications.

2. Scope

This SOP applies to all gel formulations manufactured in the production facility where pH and viscosity are critical quality attributes (CQAs) impacting product performance and stability.

3. Responsibilities

Production Operator: Collects in-process samples and performs basic pH/viscosity checks.
QC Analyst: Conducts confirmation testing using calibrated instruments and records data.
Production Supervisor: Reviews IPC results and authorizes continuation

of batch.

QA Officer: Verifies that all IPC records comply with GMP and product specifications.

4. Accountability

The Head of Manufacturing is accountable for ensuring adherence to in-process control procedures for pH and viscosity and for timely corrective action in case of deviations.

5. Procedure

5.1 pH Monitoring

Use a calibrated pH meter with appropriate electrode as per SOP/QC/027/2025.
Calibrate the pH meter daily using standard buffers (pH 4.0, 7.0, and 9.2).
Draw sample from the bulk gel during pre-dispersion, post-dispersion, and final batch stage.
Measure pH at 25°C ± 2°C and record the value in Annexure-1.
Acceptable range is product-specific; refer to the batch manufacturing record (BMR).

5.2 Viscosity Monitoring

Use a calibrated Brookfield viscometer with appropriate spindle and RPM.
Take the sample in a clean beaker; maintain the required temperature (usually 25°C ± 1°C).
Immerse spindle vertically and run for 1 minute before taking reading.
Record the viscosity in cP (centipoise) and document in Annexure-1.
Compare against approved specification limits provided in the BMR.

5.3 Frequency of Testing

pH and viscosity shall be checked during:
- Initial raw material dispersion phase
- After addition of thickening agents
- At final mixing stage before filling
Additional checks should be conducted if any adjustment is made (e.g., neutralization, solvent addition).

5.4 Deviation Handling

If pH or viscosity is out of specification (OOS), immediately notify Production and QA.
Conduct root cause analysis and document as per deviation handling SOP/QA/019/2025.
Make permissible adjustments (e.g., pH correction with NaOH or citric acid) and re-test.
Document corrective actions in Annexure-2 and the BMR.

6. Abbreviations

IPC: In-Process Control
GMP: Good Manufacturing Practices
BMR: Batch Manufacturing Record
OOS: Out of Specification
CQA: Critical Quality Attribute

7. Documents

pH and Viscosity Monitoring Log – Annexure-1
OOS/Deviation Report – Annexure-2
Batch Manufacturing Record (BMR)

8. References

USP <791> – pH Measurement
USP <911> – Viscosity Determination
SOP/QC/027/2025 – Calibration of pH Meter
SOP/QA/019/2025 – Deviation Management

9. SOP Version

Version: 2.0

10. Approval Section

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

11. Annexures

Annexure-1: pH and Viscosity Monitoring Log

Date	Batch No.	Stage	pH	Viscosity (cP)	Performed By

Annexure-2: OOS/Deviation Record

Batch No.
Date
Parameter	pH / Viscosity
OOS Value
Root Cause Analysis
Corrective Action Taken
Reviewed By
Approved By

Revision History

Revision Date	Revision No.	Change Description	Reason	Approved By
12/04/2022	1.0	Initial issue	New SOP	QA Head
09/06/2025	2.0	Clarified pH/viscosity ranges and instruments	Annual update	QA Head