Standard Operating Procedure for Calibration of pH and DO Sensors in Bioreactor Operations for Biosimilars
| Department | Biosimilars |
|---|---|
| SOP No. | SOP/BS/095/2025 |
| Supersedes | SOP/BS/095/2022 |
| Page No. | Page 1 of 11 |
| Issue Date | 04/05/2025 |
| Effective Date | 06/05/2025 |
| Review Date | 04/05/2026 |
1. Purpose
To outline the standardized procedure for calibration of pH and dissolved oxygen (DO) sensors used in bioreactor operations for biosimilar production. This ensures sensors function accurately to support optimal cell culture conditions.
2. Scope
This SOP applies to all in-situ and ex-situ pH and DO sensors used in small-scale and large-scale bioreactors in the biosimilars department.
3. Responsibilities
- Engineering: Perform sensor calibration, maintain calibration records, and ensure periodic servicing.
- Production: Verify calibrated status of sensors before every batch run.
- QA: Review calibration records and ensure SOP compliance during audits.
4. Accountability
The Engineering Manager is accountable for ensuring the calibration of pH and DO sensors is performed on schedule and meets compliance with regulatory standards.
5. Procedure
5.1 General Guidelines
- Calibrate all sensors before batch initiation and post-cleaning (CIP/SIP cycles).
- Use only traceable, certified calibration solutions and gases.
- Label sensors with calibration date, due date, and initials.
5.2 pH Sensor Calibration
- Remove sensor from bioreactor if offline or perform in-situ if reactor allows.
- Rinse sensor with distilled water and blot dry with lint-free tissue.
- Immerse sensor in pH 7.00 buffer solution; allow to stabilize and set as first calibration point.
- Rinse and then immerse in pH 4.01 or 10.01 buffer as the second calibration point (as per product requirement).
- Verify slope (acceptable range: 95%–105%) and offset (±30 mV).
- Document values in Annexure-1: pH Calibration Log.
5.3 DO Sensor Calibration
- Perform a 2-point calibration:
- Zero Calibration:
- Immerse sensor in nitrogen-sparged water or sodium sulfite solution.
- Set the output as 0% DO.
- Span Calibration:
- Expose sensor to air-saturated WFI or sparge with pure air.
- Set output as 100% DO.
- Stabilize readings before accepting each point. Acceptable sensor response time: ≤90 seconds.
- Record calibration values in Annexure-2: DO Calibration Log.
5.4 Post-Calibration Checks
- Verify calibration by checking pH and DO response in standard solutions or bioreactor media.
- Recalibrate if deviation exceeds acceptable limits.
6. Abbreviations
- DO: Dissolved Oxygen
- CIP: Clean-In-Place
- SIP: Sterilize-In-Place
- QA: Quality Assurance
7. Documents
- pH Sensor Calibration Log – Annexure-1
- DO Sensor Calibration Log – Annexure-2
8. References
- USP <1058> – Analytical Instrument Qualification
- ICH Q10 – Pharmaceutical Quality System
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 Sensor Calibration Log
| Date | Sensor ID | pH Buffers Used | Offset (mV) | Slope (%) | Calibrated By |
|---|---|---|---|---|---|
| 04/05/2025 | PH-BIO-21 | 4.01 & 7.00 | 5.2 | 98.6 | Sunita Reddy |
Annexure-2: DO Sensor Calibration Log
| Date | Sensor ID | Zero Method | Span Method | Response Time (sec) | Calibrated By |
|---|---|---|---|---|---|
| 04/05/2025 | DO-BIO-09 | Na₂SO₃ | Air-Saturated WFI | 82 | Rajesh Kumar |
Revision History:
| Revision Date | Revision No. | Revision Details | Reason for Revision | Approved By |
|---|---|---|---|---|
| 04/05/2025 | 2.0 | Added post-calibration verification and response time criteria | GMP update |