Standard Operating Procedure for Buffer Preparation for Purification Steps in Biosimilar Manufacturing

Department	Biosimilars
SOP No.	SOP/BS/176/2025
Supersedes	SOP/BS/176/2022
Page No.	Page 1 of 10
Issue Date	04/05/2025
Effective Date	06/05/2025
Review Date	04/05/2026

1. Purpose

To define the procedure for the GMP-compliant preparation, filtration, labeling, and storage of buffers used in downstream purification of biosimilar products including chromatography, viral filtration, and final formulation steps.

2. Scope

This SOP is applicable to all buffer solutions prepared within the biosimilar downstream process area for use in affinity, ion-exchange, hydrophobic interaction, SEC, and viral clearance steps.

3. Responsibilities

• Production: Prepare and filter buffers as per approved Buffer Preparation Sheets (BPS), record all entries in buffer logbook.
• QA: Verify pH, conductivity, labeling, and review all documentation.
• QC: Perform analytical release testing if required (e.g., microbial load, endotoxin).

4. Accountability

The Downstream Manufacturing Lead is accountable for ensuring the use of properly prepared and verified buffers in each batch operation.

5. Procedure

5.1 Pre-Preparation Checks

1. Verify that the buffer preparation tank, mixer, and pH/conductivity meters are cleaned and calibrated.
2. Ensure availability of approved Buffer Preparation Sheet (Annexure-1) and relevant MSDS documents.
3. Confirm material batch numbers and expiry dates for all buffer components.

5.2 Buffer Preparation Steps

1. Fill the preparation tank with pre-measured WFI or purified water as specified in the BPS.
2. Add buffer salts, acids, or bases in sequence under slow agitation using sanitized scoops or transfer lines.
3. Adjust pH to the specified value using 1 M NaOH or 1 M HCl as required.
4. Verify final conductivity and pH using calibrated meters and record results in Annexure-2.

5.3 Filtration and Transfer

1. Filter the buffer solution using 0.22 µm or 0.45 µm filters depending on usage (virus filtration/formulation vs general chromatography).
2. Transfer the filtered buffer into labeled stainless steel or single-use storage containers.
3. Attach tamper-evident seals post-filtration.

5.4 Labeling and Storage

1. Label the buffer container with the following:
   • Buffer Name
   • Batch No.
   • Date of Preparation
   • Prepared By
   • Expiry Date (as per BPS)
2. Store the buffer at the designated temperature (typically 2–8°C or room temperature) per stability data.

5.5 Documentation

1. Complete the Buffer Logbook entry with all preparation and filter details.
2. Attach filter integrity certificate if applicable.

6. Abbreviations

• BPS: Buffer Preparation Sheet
• WFI: Water for Injection
• pH: Potential of Hydrogen
• MSDS: Material Safety Data Sheet

7. Documents

1. Buffer Preparation Sheet – Annexure-1
2. pH and Conductivity Record – Annexure-2

8. References

• ICH Q7 – GMP for Active Pharmaceutical Ingredients
• USP <1227> – Validation of Compendial Procedures
• WHO TRS 999 – GMP for Biotherapeutic Products

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Buffer Preparation Sheet

Buffer Name	Components	Target pH	Conductivity (mS/cm)	Volume (L)	Expiry
Phosphate Buffer	KH₂PO₄, Na₂HPO₄	7.0	10.5	50	05/05/2025

Annexure-2: pH and Conductivity Record

Date	Buffer Name	pH	Conductivity	Tested By
04/05/2025	Phosphate Buffer	7.0	10.6 mS/cm	Sunita Reddy

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Integrated filtration and labeling instructions with annexures	Process harmonization