validated analytical techniques to ensure batch consistency and product stability.

2. Scope

This SOP applies to the Analytical Method Development and Quality Control departments engaged in characterizing polymorphism in sterile APIs during drug development, validation, and commercial batch testing.

3. Responsibilities

• Analytical Scientist: Performs solid-state analysis and interprets results from orthogonal techniques.
• R&D Chemist: Prepares and isolates different polymorphic forms for reference and comparison.
• QA Executive: Reviews data and ensures documentation compliance with regulatory requirements.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring accurate and validated characterization of polymorphic forms and for establishing controls in product specifications.

5. Procedure

5.1 Sample Preparation

1. Handle sterile API in a clean environment using sterile tools to avoid contamination or hydration.
2. Dry samples under vacuum if moisture sensitivity is known.

5.2 Techniques Used for Polymorph Characterization

• Powder X-Ray Diffraction (PXRD): Primary technique for crystallinity and phase identification
• Differential Scanning Calorimetry (DSC): For melting point and thermal behavior analysis
• Fourier-Transform Infrared Spectroscopy (FTIR): For hydrogen bonding and functional group changes
• Thermogravimetric Analysis (TGA): To detect solvate/hydrate loss
• Microscopy (Polarized Light): For visual assessment of crystal habits

5.3 PXRD Procedure

1. Mount sample on PXRD holder using back-loading method to minimize preferred orientation.
2. Scan over 2θ range from 5° to 50° at a rate of 1°/min.
3. Compare diffractograms to internal polymorph library or reference standard.

5.4 DSC Procedure

1. Weigh 2–5 mg of sample in aluminum pan.
2. Scan from 25°C to 300°C at 10°C/min under nitrogen atmosphere.
3. Record onset and peak temperatures; compare to reference form.

5.5 FTIR Analysis

1. Use ATR or KBr pellet method based on material solubility and sensitivity.
2. Record spectra between 4000 and 400 cm⁻¹.
3. Focus on regions indicating conformational differences (e.g., 1600–1700 cm⁻¹ for C=O stretching).

5.6 Data Interpretation

• Each polymorph should display distinct PXRD patterns and melting points.
• Overlay analysis of spectra and thermal profiles must confirm form identity.
• Use software tools (e.g., Origin, MDI Jade) for PXRD pattern matching and peak indexing.

5.7 Validation Parameters

1. Specificity: Method must clearly distinguish known polymorphs.
2. Precision: Reproducibility of melting point, peak position (±0.1° 2θ), and enthalpy (±5%).
3. Robustness: Evaluate consistency with sample handling variations.
4. Stability: Confirm polymorphic integrity under ICH stability conditions (e.g., 40°C/75% RH).

6. Abbreviations

• PXRD: Powder X-Ray Diffraction
• DSC: Differential Scanning Calorimetry
• FTIR: Fourier Transform Infrared Spectroscopy
• TGA: Thermogravimetric Analysis
• API: Active Pharmaceutical Ingredient

7. Documents

1. Polymorph Characterization Log – Annexure-1
2. PXRD and DSC Overlay Report – Annexure-2
3. Validation and Reference Library Summary – Annexure-3

8. References

• ICH Q6A: Specifications: Test Procedures and Acceptance Criteria
• ICH Q3C: Impurities Guidelines
• USP <941>: X-ray Diffraction
• USP <891>: Thermal Analysis

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name	Vikram Sinha	Manasi Patil	Sunita Reddy
Designation	Solid-State Analyst	QA Reviewer	Head – AMD
Department	Analytical Method Development	QA	Analytical Method Development

11. Annexures

Annexure-1: Polymorph Characterization Log

Sample ID	Method	Form Identified	Melting Point (°C)	Status
POLY-280-01	PXRD	Form II	175.8	Pass

Annexure-2: PXRD and DSC Overlay Report

Includes diffractogram overlays and thermal analysis showing distinct melting behavior of Form I vs. Form II for the API.

Annexure-3: Validation and Reference Library Summary

Validated reference spectra and thermal data compiled for Forms I–IV of the API. Peak indexing and diffraction angles included for comparison during routine analysis.

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
21/05/2025	2.0	Included TGA and ATR-FTIR options, expanded validation criteria	Annual Review	Sunita Reddy
11/05/2022	1.0	Initial SOP Release	New SOP	QA Head