fingerprint and functional group regions.

2. Scope

This SOP is applicable to all FTIR-based identity and fingerprint tests performed in the Analytical Method Development (AMD) laboratory using the KBr pellet method for APIs, intermediates, and excipients.

3. Responsibilities

• Analytical Chemist: Prepares KBr pellets, performs spectrum acquisition, and evaluates pellet quality.
• Method Reviewer: Assesses pellet consistency and verifies optimization logs.
• QA Officer: Confirms compliance with GMP and regulatory expectations for spectral accuracy and reproducibility.
• Head – AMD: Ensures approval of optimization data and authorizes use in validated procedures.

4. Accountability

The Head of Analytical Method Development is accountable for maintaining the consistency, reproducibility, and regulatory compliance of FTIR results derived using the KBr pellet method.

5. Procedure

5.1 Reagents and Equipment

1. Potassium Bromide (IR Grade): Use only spectroscopic-grade KBr, stored in a desiccator.
2. Pellet Press: Hydraulic press with 10 mm die and polished stainless steel components.
3. Mortar and Pestle: Agate or borosilicate for sample-KBr mixing.
4. Desiccator: Silica-gel packed vacuum desiccator for pellet storage.

5.2 Drying of KBr and Samples

1. Place sufficient quantity (~5 g) of KBr in a clean porcelain crucible.
2. Dry at 105°C in a hot air oven for 2 hours.
3. Cool in a desiccator for 30 minutes before use.
4. For moisture-sensitive APIs, dry sample as per stability profile and document in Annexure-1: Drying Record.

5.3 Sample-to-KBr Ratio Optimization

1. Weigh sample and KBr in different proportions:
   • Option 1: 1 mg sample + 100 mg KBr (1% w/w)
   • Option 2: 2 mg sample + 200 mg KBr (1% w/w)
   • Option 3: 2 mg sample + 100 mg KBr (2% w/w)
2. Grind each mixture for 2–3 minutes in agate mortar until homogeneous and free-flowing.
3. Press pellets under 10-ton pressure for 1–2 minutes using hydraulic press.
4. Document pressure, ratio, and clarity outcome in Annexure-2: Optimization Matrix.

5.4 Evaluation of Pellet Quality

1. Pellet should be transparent and free from cracks or surface irregularities.
2. Visually inspect clarity against white paper background.
3. Poorly prepared pellets will scatter IR radiation and distort spectra.
4. Log observations in Annexure-3: Pellet Clarity Evaluation Log.

5.5 FTIR Scanning and Spectrum Quality

1. Collect background using blank KBr pellet before each scan.
2. Scan the sample pellet using:
   • Range: 4000–400 cm^-1
   • Resolution: 4 cm^-1
   • Scans: 32–64
3. Evaluate signal-to-noise ratio, peak sharpness, and fingerprint region clarity.
4. Compare spectra from each pellet type to identify the most reproducible and high-quality spectrum.
5. Record FTIR scan comparison in Annexure-4: Spectral Quality Comparison.

5.6 Finalization of Optimized Method

1. Choose the sample-to-KBr ratio and compression conditions that yield:
   • High peak intensity
   • Clear baseline
   • Minimal spectral noise
2. Fix this ratio as the standard for subsequent method development and validation.
3. Document optimization summary in Annexure-5: Method Finalization Sheet.

6. Abbreviations

• FTIR: Fourier Transform Infrared
• KBr: Potassium Bromide
• SOP: Standard Operating Procedure
• API: Active Pharmaceutical Ingredient
• w/w: Weight/Weight
• cm^-1: Wavenumber

7. Documents

1. Drying Record – Annexure-1
2. Optimization Matrix – Annexure-2
3. Pellet Clarity Evaluation Log – Annexure-3
4. Spectral Quality Comparison – Annexure-4
5. Method Finalization Sheet – Annexure-5

8. References

• ICH Q2(R1) – Validation of Analytical Procedures
• USP <197K> – Infrared Spectrophotometry
• FTIR Instrument User Manual
• Pharmaceutical Spectroscopy Reference Books

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: Drying Record

Material	Drying Temp (°C)	Duration (min)	Start Time	End Time	Remarks
KBr	105	120	10:00	12:00	Dried

Annexure-2: Optimization Matrix

Sample (mg)	KBr (mg)	Ratio (%)	Pressure (tons)	Pellet Status
1	100	1%	10	Clear
2	100	2%	10	Hazy

Annexure-3: Pellet Clarity Evaluation Log

Sample ID	Visual Clarity	Cracks Observed	Acceptable (Y/N)
KBR-098-01	Transparent	No	Y

Annexure-4: Spectral Quality Comparison

Sample ID	Signal-to-Noise Ratio	Peak Shape	Baseline Stability	Conclusion
KBR-098-01	High	Sharp	Stable	Best

Annexure-5: Method Finalization Sheet

Final Ratio (Sample:KBr)	Pressure (tons)	Scan Settings	Approved By
1:100	10	4000–400 cm-1, 4 cm-1, 64 scans

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Added annexures for pellet clarity and spectral quality evaluation	Annual SOP Review