determination is required.

3. Responsibilities

• Quality Control Analyst: To perform the pH test and record accurate results.
• QC Supervisor: To review and verify the accuracy and compliance of the recorded data.
• QA Officer: To ensure the procedure aligns with applicable guidelines and SOPs.

4. Accountability

The Head – Quality Control shall be accountable for the implementation and compliance of this SOP.

5. Procedure

5.1 Instrumentation

• Use a calibrated digital pH meter with electrode suitable for semi-solid samples.
• Ensure that the instrument is properly maintained and documented as per calibration SOP.

5.2 Reagents and Materials

• pH buffer solutions (pH 4.0, 7.0, and 9.2)
• Distilled or purified water
• Beakers and glass rods
• Clean spatula for sample transfer

5.3 Sample Preparation

1. Using a clean spatula, take about 1–2 g of the gel sample into a clean beaker.
2. Dilute with an appropriate quantity of purified water if required (as per test method).
3. Stir gently to homogenize the sample.

5.4 Calibration of pH Meter

1. Calibrate the pH meter with buffer solutions of pH 4.0, 7.0, and 9.2.
2. Record calibration details in the instrument logbook.

5.5 Measurement of pH

1. Rinse the electrode with distilled water before dipping into the sample.
2. Immerse the electrode into the prepared sample and allow the reading to stabilize.
3. Record the pH value once it stabilizes (within 30 seconds).
4. Rinse electrode again before storing in storage solution.

5.6 Acceptance Criteria

• pH value should be within the specified range for the gel product as per product specification (typically 4.5 to 7.5 depending on formulation).

5.7 Documentation

1. Record the result in the pH test logbook and on the Analytical Worksheet.
2. Attach a copy of calibration data and sampling sheet.
3. Submit all entries for review and final QA approval.

6. Abbreviations

• QA: Quality Assurance
• QC: Quality Control
• SOP: Standard Operating Procedure
• pH: Potential of Hydrogen

7. Documents

1. pH Test Logbook – Annexure-1
2. Analytical Worksheet – Annexure-2
3. Calibration Logbook – Annexure-3

8. References

• USP General Chapter <791> – pH
• ICH Q6A – Specifications: Test Procedures and Acceptance Criteria
• Internal Product Specifications

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: pH Test Logbook Format

Date	Product Name	Batch No.	Sample Location	Tested By	pH Value	Remarks
			Top
			Middle
			Bottom

Annexure-2: Analytical Worksheet Template

Product	Batch No.	Date	Sample Point	pH Measured	Analyst	Reviewed By

Annexure-3: Calibration Logbook Format

Date	Instrument ID	Buffer Used	Calibration Point	Result	Performed By	Reviewed By
		pH 4.0	4.00 ± 0.05
		pH 7.0	7.00 ± 0.05
		pH 9.2	9.20 ± 0.05

Revision History

Revision Date	Revision No.	Details	Reason	Approved By
13/05/2022	1.0	Initial version prepared	New SOP	QA Head
02/06/2025	2.0	Format updated, annexures added, calibration logbook included	Compliance with audit feedback	QA Head