Standard Operating Procedure for pH Testing of Cream Products

Department	Creams
SOP No.	SOP/CRM/123/2025
Supersedes	SOP/CRM/123/2022
Page No.	Page 1 of 5
Issue Date	21/01/2026
Effective Date	26/01/2026
Review Date	21/01/2027

1. Purpose

The purpose of this SOP is to define the procedure for testing the pH of cream products to ensure that they meet the required pH range for safety, stability, and product efficacy. Proper pH control ensures the quality and safety of the final cream product and prevents potential irritation or instability.

2. Scope

This SOP applies to all cream formulations produced in the facility, both during the manufacturing process and as part of the final product testing. It includes guidelines for sampling, pH testing, and documentation for quality control purposes.

3. Responsibilities

• Production Team: Responsible for collecting samples at specified stages of the production process (e.g., after mixing, before packaging) for pH testing and ensuring that samples are delivered to the QC laboratory.
• Quality Control (QC) Team: Responsible for performing the pH testing of cream formulations using calibrated pH meters and ensuring that the results meet the established specifications.
• Quality Assurance (QA) Team: Responsible for reviewing the pH test results to ensure compliance with GMP standards and verifying that all documentation is complete and accurate.

4. Accountability

The QC Manager is accountable for ensuring that pH testing is performed accurately and according to the procedure. The Production Supervisor is responsible for ensuring proper sampling at various stages of production. The QA Manager ensures overall compliance with regulatory standards and GMP guidelines.

5. Procedure

5.1 Pre-Test Preparation

1. Ensure that all necessary equipment and supplies are available and properly calibrated, including pH meters, buffers, and sample containers. Calibrate the pH meter using appropriate calibration standards (e.g., pH 4.0, 7.0, 10.0 buffers) according to the manufacturer’s instructions.
2. Review the product batch record to determine the appropriate stages of sampling for pH testing, ensuring that the sample is representative of the product.
3. Ensure that all testing is conducted in a clean and controlled environment to prevent cross-contamination of samples.

5.2 Sample Collection

1. Collect samples of the cream formulation from the designated points in the production process (e.g., after mixing, before filling). Ensure that the sample is taken using a clean, sterile tool to avoid contamination.
2. Label the sample with relevant information, including the batch number, sampling date, sampling point, and sample ID.
3. If necessary, dilute the sample with distilled water to ensure that the pH can be accurately measured. Ensure that the dilution ratio is noted in the testing log.

5.3 pH Testing Procedure

1. Ensure that the pH meter is calibrated before performing the test. If the pH meter requires manual calibration, follow the manufacturer’s instructions to ensure accurate results.
2. Place the electrode of the pH meter into the cream sample and stir gently to allow the electrode to measure the pH accurately. Avoid excessive stirring, as it may introduce air bubbles that could affect the measurement.
3. Record the pH value once it has stabilized. If the pH value fluctuates or does not stabilize, repeat the measurement to ensure accuracy.
4. If multiple samples are collected from different batches or stages, perform the same pH testing procedure for each sample and record the results separately in the testing log (Annexure-1).

5.4 Interpretation of Results

1. Compare the measured pH value with the acceptable pH range specified for the cream formulation. The typical pH range for most cream formulations is between 4.0 and 7.0, though the exact range may vary based on the product formulation.
2. If the pH value is within the specified range, mark the test as “Pass” in the pH testing log.
3. If the pH value falls outside of the acceptable range, mark the test as “Fail” and investigate the cause of the deviation. Common causes of pH deviations may include improper formulation or contamination during production.

5.5 Post-Test Activities

1. Record all pH testing results, including batch number, sample ID, test results, and any corrective actions taken in the pH Testing Log (Annexure-1).
2. If a sample fails the pH test, investigate the cause of the failure, which may include reviewing the formulation, ingredient sourcing, or production process. Document any corrective actions taken in the Deviation Log (Annexure-2).
3. If necessary, re-test the cream formulation after corrective actions have been implemented to ensure that the pH is within the acceptable range.

5.6 Documentation and Record-Keeping

1. Ensure that all pH testing records are complete, accurate, and stored securely. This includes the pH Testing Log (Annexure-1) and the Deviation Log (Annexure-2) for any failed tests.
2. Maintain all records for a minimum of two years or as per regulatory guidelines.
3. Ensure that records are reviewed by the QA team to verify compliance with GMP standards and regulatory requirements.

6. Abbreviations

• GMP: Good Manufacturing Practices
• QC: Quality Control
• QA: Quality Assurance
• PPE: Personal Protective Equipment

7. Documents

1. Annexure-1: pH Testing Log
2. Annexure-2: Deviation Log

8. References

• Good Manufacturing Practices (GMP) Guidelines – 21 CFR Part 211
• International Conference on Harmonisation (ICH) Q7 – Good Manufacturing Practice for Active Pharmaceutical Ingredients
• Manufacturer’s Manual for pH Meters

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: pH Testing Log

Batch Number	Sample ID	Sampling Date	pH Value	Operator
12345	S-001	21/01/2026	5.5	John Doe

Annexure-2: Deviation Log

Deviation Date	Batch Number	Deviation Description	Corrective Action Taken	Operator
21/01/2026	12345	pH value outside range	Adjusted formulation, re-tested	Jane Smith

Revision History:

Revision Date	Revision No.	Revision Details	Reason for Revision	Approved By
01/03/2024	1.0	Initial Version	New SOP Creation	QA Head
01/03/2025	2.0	Format Revision and Updates	Standardization of Document	QA Head