during batch release, stability studies, or regulatory submissions.

3. Responsibilities

• QC Analyst: Prepare samples and standards, perform HPLC runs, integrate peaks, and calculate impurity levels.
• QC Reviewer: Review chromatograms, retention times, and impurity limits compliance.
• QA Officer: Verify results and ensure traceability for regulatory audits and documentation.

4. Accountability

The QC Head is accountable for ensuring that impurity testing procedures are scientifically justified, properly documented, and in accordance with approved analytical methods.

5. Procedure

5.1 Reference Documents and Preparation

1. Refer to the approved analytical method or pharmacopoeial monograph for:
   • Mobile phase composition
   • Column specification
   • Detector wavelength
   • Injection volume and flow rate
2. Prepare impurity standards and working standards in accordance with method SOPs.

5.2 System Suitability

1. Inject system suitability solution or standard mixture containing known impurities.
2. Ensure:
   • Resolution between critical peaks ≥ 2.0
   • Retention time repeatability within ±2%
   • %RSD of impurity area for repeat injections ≤ 10%

5.3 Sample Injection and Data Acquisition

1. Inject test solution and record chromatograms under validated conditions.
2. Identify peaks based on relative retention time (RRT) compared to standard.
3. Integrate all peaks above 0.05% (unless otherwise justified in validation).

5.4 Quantification

1. Calculate individual impurity % using response factor or area normalization method as per method validation.
2. Total impurity = sum of all impurities above threshold level.
3. Compare with acceptance criteria from:
   • ICH Q3A/B
   • Regulatory filing (e.g., DMF)
   • In-house specifications

5.5 Reporting Format

1. Report impurity profiling in the Impurity Profiling Report Sheet (Annexure-1) with:
   • Impurity name/RRT
   • Retention time
   • Observed area
   • Calculated percentage
   • Limit
   • Status (Pass/Fail)

5.6 Investigation of Unidentified Peaks

1. Any unknown impurity above reporting threshold must be:
   • Assigned an RRT and tracked in stability studies
   • Subject to identification via MS/NMR if consistently observed
   • Considered for toxicological evaluation if >0.1%

6. Abbreviations

• API: Active Pharmaceutical Ingredient
• HPLC: High-Performance Liquid Chromatography
• RRT: Relative Retention Time
• RSD: Relative Standard Deviation
• DMF: Drug Master File
• ICH: International Council for Harmonisation

7. Documents

1. Impurity Profiling Report Sheet (Annexure-1)
2. System Suitability Checklist
3. Instrument Run Sequence

8. References

• ICH Q3A – Impurities in New Drug Substances
• ICH Q3B – Impurities in New Drug Products
• USP <621>, <466>, and applicable monographs

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Impurity Profiling Report Sheet

RRT	Retention Time	Peak Area	% Impurity	Limit	Status
0.72	5.23	10234	0.12%	NMT 0.15%	Pass
1.00	6.54	78543	0.88%	NMT 1.0%	Pass
1.35	8.40	17645	0.25%	NMT 0.2%	Fail

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
01/01/2022	1.0	Initial Issue	New SOP	QA Head
13/04/2025	2.0	Updated impurity calculation and unknown investigation	Audit Compliance	QA Head