Standard Operating Procedure for Conductivity Measurement in Process Solutions in API Manufacturing

Department	API Manufacturing
SOP No.	SOP/API/084/2025
Supersedes	SOP/API/084/2022
Page No.	Page 1 of 10
Issue Date	13/04/2025
Effective Date	15/04/2025
Review Date	13/04/2026

1. Purpose

To describe a standardized method for measuring the conductivity of process solutions in API manufacturing to monitor ionic strength, validate cleaning processes, and ensure consistency in intermediate reactions and aqueous washings.

2. Scope

This SOP applies to conductivity checks performed during aqueous extractions, reaction monitoring, washing of intermediates, and equipment cleaning verification in the API manufacturing facility.

3. Responsibilities

• Production Chemist/Operator: Collect and measure samples as per process instructions.
• QC Analyst: Verify conductivity meter calibration and review results.
• QA Officer: Audit logbooks and ensure compliance with procedural accuracy.

4. Accountability

The Production Head is accountable for operational control. The QC Head is responsible for analytical accuracy and data integrity.

5. Procedure

5.1 Instrument Calibration

1. Calibrate the conductivity meter using certified standard solutions (e.g., 84 µS/cm and 1413 µS/cm) as per manufacturer’s instructions.
2. Document calibration readings in the Conductivity Meter Calibration Log (Annexure-1).
3. Do not use equipment with expired calibration or with deviation in standard reading beyond ±2%.

5.2 Sample Collection

1. Collect process solution in clean, dry, and inert beakers or flasks.
2. If sampling from a reactor or tank, ensure sample represents bulk solution and not surface layer.
3. Allow solution to cool if collected from hot reaction mass (not above 40°C unless validated).

5.3 Measurement Technique

1. Rinse the conductivity probe with distilled water and pat dry with lint-free tissue.
2. Insert the probe into the sample ensuring full immersion of electrodes.
3. Allow the reading to stabilize (typically 30 seconds to 1 minute).
4. Record the value in µS/cm or mS/cm along with temperature (if auto-compensated).
5. Document the reading in the Conductivity Measurement Log (Annexure-2) and BMR.

5.4 Acceptance Criteria and Interpretation

1. Refer to the approved process or cleaning validation protocol for acceptance ranges (e.g., conductivity NMT 10 µS/cm for final rinse).
2. If outside limit, notify QA and repeat measurement using fresh sample.
3. Initiate deviation report if reading remains out of specification.

5.5 Post-Use Maintenance

1. After use, rinse the probe thoroughly with distilled water and store in 3M KCl or as recommended.
2. Turn off the instrument and cover the probe to avoid dust or drying.

6. Abbreviations

• SOP: Standard Operating Procedure
• QA: Quality Assurance
• QC: Quality Control
• BMR: Batch Manufacturing Record
• µS/cm: Microsiemens per centimeter
• mS/cm: Millisiemens per centimeter

7. Documents

1. Conductivity Meter Calibration Log (Annexure-1)
2. Conductivity Measurement Log (Annexure-2)
3. Batch Manufacturing Record

8. References

• ICH Q2(R1) – Validation of Analytical Procedures
• 21 CFR Part 211 – US FDA cGMP
• WHO TRS 986 – Good Manufacturing Practices

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Conductivity Meter Calibration Log

Date	Meter ID	Standard Used	Expected Value	Observed Value	Calibrated By	Remarks
13/04/2025	CD-01	1413 µS/cm	1413	1410		Within range

Annexure-2: Conductivity Measurement Log

Date	Batch No.	Process Stage	Conductivity (µS/cm)	Temperature (°C)	Measured By	Remarks
13/04/2025	API-20250413	Post-Wash	8.7	28		Within limit

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
01/01/2022	1.0	Initial Release	New Instrument Control SOP	QA Head
13/04/2025	2.0	Added interpretation and deviation handling steps	Audit Compliance	QA Head