the presence of other expected components such as impurities, degradants, and excipients.

2. Scope

This SOP is applicable to all analytical methods developed and validated for the assessment of drug substances, drug products, excipients, and cleaning samples within the Analytical Method Development (AMD) department.

3. Responsibilities

• Analytical Scientist: Designs and performs specificity studies including interference checks.
• Validation Analyst: Conducts injections of blank, placebo, standard, sample, and degraded solutions.
• QA Officer: Reviews data, chromatograms, and overlay results for compliance with regulatory expectations.
• Head – AMD: Approves the final validation report and ensures regulatory alignment.

4. Accountability

The Head of AMD is accountable for ensuring that all validated methods are proven to be specific as per ICH Q2(R2) and internal quality systems.

5. Procedure

5.1 Preparation of Samples

1. Prepare the following for testing:
   • Blank (diluent)
   • Placebo (formulation without API)
   • Standard solution
   • Test sample
   • Spiked sample (API + placebo)
   • Forced degradation sample (acid/base/oxidation/heat/light)

5.2 Chromatographic Evaluation

1. Inject each sample individually and obtain chromatograms.
2. Overlay chromatograms of standard, placebo, blank, and degraded samples.
3. Check for:
   • No co-eluting peaks at retention time (RT) of analyte
   • No significant peak in blank and placebo
   • Proper resolution between API and degradants (Rs ≥ 2.0)

5.3 Peak Purity Assessment

1. Use PDA detection to calculate:
   • Purity angle
   • Purity threshold
2. If purity angle < purity threshold, consider the peak specific.

5.4 Documentation and Acceptance Criteria

1. Record all injections, system suitability, and chromatographic overlays in Annexure-1: Specificity Validation Report.
2. Acceptance criteria:
   • No interference at RT of analyte from blank, placebo, or degradants
   • Peak purity confirmed
   • API and impurity peaks resolved (Rs ≥ 2.0)

6. Abbreviations

• API: Active Pharmaceutical Ingredient
• PDA: Photodiode Array Detector
• RT: Retention Time
• Rs: Resolution
• ICH: International Council for Harmonisation

7. Documents

1. Specificity Validation Report – Annexure-1

8. References

• ICH Q2(R2) – Validation of Analytical Procedures
• FDA Guidance – Analytical Method Validation
• Internal Validation SOP – Method Specificity

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Specificity Validation Report

Sample Type	RT (min)	Co-elution Observed	Purity Angle	Purity Threshold	Conclusion
Standard	5.72	No	0.221	0.318	Pass
Placebo	—	No	—	—	No Interference
Degraded Sample	5.74	No	0.229	0.336	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Updated PDA usage and resolution acceptance criteria	Regulatory harmonization