for in-process and final pH checks in gel formulation and production units.

3. Responsibilities

• Production Chemist: Performs calibration and routine maintenance.
• QA Executive: Verifies calibration records and ensures compliance.
• Engineering Technician: Supports troubleshooting and annual maintenance.

4. Accountability

Head – Manufacturing

5. Procedure

5.1 Equipment and Reagents Required

1. pH meter (calibrated internally)
2. Standard buffer solutions (pH 4.01, 7.00, and 9.20)
3. Distilled or deionized water
4. Cleaning tissue or lint-free cloth

5.2 Calibration Procedure

1. Switch on the pH meter and allow stabilization for 10 minutes.
2. Rinse electrode with distilled water and gently blot dry.
3. Immerse electrode into pH 7.00 buffer. Wait until reading stabilizes and press ‘calibrate.’
4. Repeat with pH 4.01 and pH 9.20 buffers (as applicable for the product range).
5. Calibration is considered successful if error is within ±0.05 pH units.
6. Record calibration data in the pH Meter Calibration Log (Annexure-1).

5.3 Maintenance Procedure

1. Clean electrode daily with distilled water and once a week with electrode cleaning solution.
2. Store the electrode in recommended storage solution when not in use.
3. Check for cracks, dried gel, or discoloration before each use.
4. Replace electrodes as per manufacturer recommendation or if faulty response is detected.

5.4 Troubleshooting

1. If drift is observed in readings, clean and re-calibrate the electrode.
2. If unstable readings persist, check for loose cables and power supply.
3. Escalate unresolved issues to Engineering or QA.

6. Abbreviations

• QA: Quality Assurance
• GMP: Good Manufacturing Practice
• pH: Potential of Hydrogen

7. Documents

1. pH Meter Calibration Log – Annexure-1
2. Maintenance Checklist – Annexure-2
3. Deviation Report (if calibration fails)

8. References

• Manufacturer’s Manual of pH Meter
• ICH Q2(R1): Validation of Analytical Procedures
• GMP Guidelines – Schedule M

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 Meter Calibration Log

Date	Time	Buffer Used	Observed Reading	Corrected?	Performed By	Remarks

Annexure-2: Maintenance Checklist

Date	Cleaning Performed	Electrode Condition	Storage Checked	Performed By	Remarks

Revision History

Revision Date	Revision No.	Change Description	Reason	Approved By
12/02/2022	1.0	Initial issue	New SOP	QA Head
09/06/2025	2.0	Updated calibration intervals and troubleshooting guidance	Annual review	QA Head