specifications.

2. Scope

This SOP applies to Analytical Method Development and Quality Control personnel responsible for pH analysis of topical and transdermal semi-solid dosage forms during formulation development, stability testing, and batch release.

3. Responsibilities

• Analytical Scientist: Performs pH measurement using calibrated instruments and documents data.
• QC Analyst: Prepares sample dispersions and supports equipment maintenance.
• QA Executive: Verifies pH data and ensures adherence to protocol and specification limits.

4. Accountability

The Head of Analytical Method Development is accountable for the implementation, validation, and compliance of pH measurement methods for semi-solid dosage forms.

5. Procedure

5.1 Instrument and Materials

1. pH Meter (with temperature compensation)
2. Combination electrode suitable for semi-solid matrices (e.g., flat membrane or spear-type)
3. Standard pH buffers (pH 4.00, 7.00, 10.00)
4. Deionized water, beakers, spatula, watch glass

5.2 Calibration of pH Meter

1. Calibrate the pH meter daily using at least two standard buffers bracketing the expected sample pH.
2. Document calibration results and ensure slope is within 95%–105% range.

5.3 Sample Preparation

1. Weigh 1 g of semi-solid formulation into a clean 50 mL beaker.
2. Add 10 mL of deionized water or suitable diluent.
3. Stir gently with a glass rod or magnetic stirrer to form a uniform dispersion.
4. Allow the dispersion to equilibrate for 10 minutes at room temperature (25 ± 2°C).

5.4 pH Measurement

1. Rinse electrode with deionized water and blot gently with lint-free tissue.
2. Insert electrode into the dispersion ensuring good contact with the sample.
3. Allow reading to stabilize for 30–60 seconds.
4. Record pH value and repeat the test in duplicate.

5.5 Acceptance Criteria

• Typical acceptable pH range: 4.0 to 7.5 (unless otherwise specified by product requirements)
• Triplicate readings must not differ by more than ±0.1 units.

5.6 Precautions

1. Do not immerse electrode beyond recommended depth.
2. Use specific electrode designed for viscous or semi-solid matrices.
3. Do not allow sample to dry on electrode surface; rinse immediately after use.

5.7 Documentation

1. Record pH meter ID, buffer batch numbers, calibration results, and sample data in the pH Test Log.
2. Attach printouts or screenshots (if applicable) and analyst initials.

6. Abbreviations

• pH: Potential of Hydrogen
• QA: Quality Assurance
• AMD: Analytical Method Development
• RSD: Relative Standard Deviation

7. Documents

1. pH Test Log Sheet – Annexure-1
2. pH Meter Calibration Record – Annexure-2

8. References

• USP General Chapter <791>: pH
• ICH Q6A: Specifications – Test Procedures and Acceptance Criteria
• EP 2.2.3: Potentiometric Determination of pH

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Anjali Patil	Sachin Kale	Sunita Reddy
Designation	Analytical Chemist	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: pH Test Log Sheet

Batch No.	Formulation	Reading 1	Reading 2	Reading 3	Average	Status
SS-255-01	Hydrocortisone Cream 1%	6.25	6.26	6.24	6.25	Pass

Annexure-2: pH Meter Calibration Record

Date	pH Meter ID	Buffer Used	Measured Value	Status
21/05/2025	PHM-08	pH 4.00 / 7.00	4.01 / 6.99	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Clarified dispersion preparation and acceptance range	Annual SOP Review	Sunita Reddy
05/03/2022	1.0	Initial Release	New SOP	QA Head