Procedure for pH Measurement of Solutions
1) Purpose
The purpose of this SOP is to outline the procedure for accurately measuring the pH of solutions used in pharmaceutical manufacturing to ensure consistency and quality.
2) Scope
This SOP applies to all solutions used within the manufacturing facility that require pH measurement.
3) Responsibilities
Quality Control (QC) Department: Responsible for conducting pH measurements and ensuring compliance with this SOP.
Production Department: Responsible for preparing solutions and providing samples for pH testing.
4) Procedure
4.1 Equipment Preparation:
4.1.1 Ensure the pH meter is calibrated using standard buffer solutions (pH 4.0, 7.0, and 10.0) before starting measurements.
4.1.2 Rinse the pH electrode with distilled water and gently blot dry with a lint-free tissue between measurements.
4.1.3 Place the electrode into the solution to be tested, ensuring it is fully submerged and stable.
4.2 pH Measurement Procedure:
4.2.1 Allow the pH reading to stabilize as per the manufacturer’s instructions (typically 30 seconds to 1 minute).
4.2.2 Record the pH value once the reading stabilizes.
4.2.3 Repeat the measurement at least three times for each sample to ensure accuracy and consistency.
4.2.4 If necessary, adjust the pH of the solution within specified limits using suitable acid or base solutions under controlled conditions.
4.3 Calibration Check:
4.3.1 Perform a calibration check of the pH meter at regular intervals during testing using fresh buffer solutions.
4.3.2 Document the calibration check results and take corrective actions if the pH meter does not meet acceptance criteria.
4.4 Acceptance Criteria:
4.4.1 The pH of the solution meets the specified range or target value as per product requirements.
4.4.2 pH meter calibration check is within acceptable limits (e.g., deviation from standard buffer solutions is within ±0.1 pH units).
4.5 Documentation:
4.5.1 Record all pH measurements, calibration checks, adjustments made (if any), and any deviations from expected values in the pH Measurement Record.
4.5.2 Review and approve the documentation by QC Manager.
5) Abbreviations, if any
QC: Quality Control
pH: Potential of Hydrogen
6) Documents, if any
pH Measurement Record
Calibration Record for pH Meter
Sampling Plan Document
7) Reference, if any
USP General Chapter <791> – pH
21 CFR Part 211 – Current Good Manufacturing Practice for Finished Pharmaceuticals
8) SOP Version
Version 1.0