pharmaceutical ingredients (API) or excipients, thus preserving the integrity of the analytical results.

2. Scope

This SOP applies to all filter compatibility assessments performed for analytical methods developed or validated within the Analytical Method Development (AMD) department for pharmaceutical formulations and API samples.

3. Responsibilities

• Analytical Scientist: Responsible for planning and executing the filter compatibility study.
• QA Reviewer: Ensures that the filter study design and outcomes meet compliance and documentation standards.
• Section Head – AMD: Reviews and approves the filter compatibility study report.

4. Accountability

The Head of Analytical Method Development shall ensure that all filter compatibility studies are performed per this SOP and documented according to current regulatory expectations (e.g., FDA, ICH, WHO, CDSCO).

5. Procedure

5.1 Selection of Filters

1. Identify filters based on chemical compatibility with diluent or sample matrix (e.g., Nylon, PVDF, PTFE, PES, RC).
2. Select at least two different filter types and one unfiltered control for comparative analysis.
3. Ensure filters have a pore size of 0.22 µm or 0.45 µm as appropriate to the method.

5.2 Preparation of Test Solutions

1. Prepare standard solution of the target analyte in diluent as per method SOP.
2. Divide into three aliquots:
   • One to be filtered through Filter A
   • One through Filter B
   • One unfiltered as control
3. Filter the respective aliquots through the filters under identical conditions.

5.3 Chromatographic Evaluation

1. Inject each aliquot in triplicate into the chromatographic system (e.g., HPLC).
2. Compare the chromatograms for retention time, peak shape, area, and recovery percentage.
3. Evaluate any changes in signal-to-noise ratio or baseline drift.

5.4 Data Analysis and Interpretation

1. Calculate the percentage recovery for Filter A and Filter B against the unfiltered control.
2. Acceptable recovery range: 98%–102% of unfiltered sample.
3. Document and justify the selected filter based on recovery, peak shape, and absence of interference.

5.5 Documentation

1. Use Annexure-1: Filter Compatibility Worksheet to record results, chromatograms, and observations.
2. Attach instrument printouts, integration data, and chromatographic conditions as part of the report.
3. Ensure the study is reviewed and approved before finalizing method validation.

6. Abbreviations

• HPLC: High Performance Liquid Chromatography
• PVDF: Polyvinylidene Difluoride
• PTFE: Polytetrafluoroethylene
• PES: Polyethersulfone
• RC: Regenerated Cellulose
• QA: Quality Assurance

7. Documents

1. Annexure-1: Filter Compatibility Worksheet
2. Annexure-2: Recovery Calculation Template
3. Annexure-3: Filter Certificate of Analysis

8. References

• ICH Q2(R1): Validation of Analytical Procedures
• FDA Guidance for Industry – Analytical Procedures and Methods Validation
• USP General Chapter <1058> Analytical Instrument Qualification

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Manoj Kumar	Deepa Ghosh	Dr. A. N. Sharma
Designation	Method Development Scientist	QA Officer	Head – AMD
Department	Analytical Method Development	Quality Assurance	Analytical Method Development

11. Annexures

Annexure-1: Filter Compatibility Worksheet

Sample	Filter Type	Peak Area	% Recovery	Comment
Standard	Unfiltered	10520	100%	Control
Standard	Filter A (PTFE)	10480	99.6%	Accepted
Standard	Filter B (Nylon)	10510	99.9%	Accepted

Annexure-2: Recovery Calculation Template

% Recovery = (Peak Area of Filtered Sample / Peak Area of Unfiltered Sample) × 100

Annexure-3: Filter Certificate of Analysis

Attach manufacturer’s CoA for each filter used in the study including material compatibility, pore size, and batch number.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
01/06/2025	2.0	Expanded scope and included annexure templates	Annual SOP review	Dr. A. N. Sharma
20/04/2022	1.0	Initial Release	New SOP	QA Head