Standard Operating Procedure for Development of 1H NMR Method in Analytical Method Development

Department	Analytical Method Development
SOP No.	SOP/AMD/111/2025
Supersedes	SOP/AMD/111/2022
Page No.	Page 1 of 14
Issue Date	19/05/2025
Effective Date	20/05/2025
Review Date	19/05/2026

1. Purpose

This SOP outlines the systematic procedure for developing and optimizing proton nuclear magnetic resonance (1H NMR) methods for structural elucidation, qualitative identification, and quantitative analysis of pharmaceutical substances and impurities.

2. Scope

This SOP applies to all 1H NMR method development activities for drug substances, intermediates, and impurities in the Analytical Method Development (AMD) laboratory. It includes method setup, parameter optimization, sample preparation, and interpretation guidelines.

3. Responsibilities

• NMR Analyst: Prepares samples, sets up instrument parameters, acquires spectra, and interprets results.
• Analytical Scientist: Assesses spectral quality, validates assignments, and supports quantification trials.
• QA Officer: Reviews and verifies method development documentation and reports.
• Head – AMD: Approves finalized methods and ensures regulatory compliance.

4. Accountability

The Head of Analytical Method Development is accountable for ensuring that all 1H NMR methods developed are scientifically valid, properly documented, and suitable for intended applications such as structure confirmation and impurity profiling.

5. Procedure

5.1 Sample Preparation

1. Weigh 10–20 mg of the test sample into a clean dry vial.
2. Add 0.6 mL of deuterated solvent (e.g., DMSO-d₆, CDCl₃, D₂O) depending on solubility and chemical compatibility.
3. Vortex or sonicate gently to ensure complete dissolution.
4. Transfer the solution to a clean 5 mm NMR tube using a dry Pasteur pipette.
5. Label the tube clearly with sample code and analyst initials.
6. Document preparation in Annexure-1: NMR Sample Preparation Log.

5.2 Instrument Configuration

1. Use a calibrated NMR spectrometer (400–600 MHz) equipped with appropriate probe and temperature regulation.
2. Set default acquisition parameters:
   • Pulse sequence: Standard 1D proton (zg)
   • Spectral width: ~12 ppm
   • Number of scans: 8–64 (depending on concentration and sensitivity)
   • Relaxation delay: ≥ 5 × T1 (typically 2–5 seconds)
   • Acquisition time: ~2–3 seconds
   • Receiver gain: Auto or set based on baseline noise
3. Lock, shim, and tune the instrument for each solvent/sample.
4. Record all settings in Annexure-2: Instrument Setup Log.

5.3 Spectral Acquisition

1. Acquire the 1H NMR spectrum using the parameters in Section 5.2.
2. Verify:
   • Solvent peak identification
   • Lock and shim stability
   • Line shape and signal-to-noise ratio
3. If required, increase number of scans to improve resolution or signal clarity.
4. Use baseline correction and phase adjustment functions post-acquisition.
5. Save raw data and processed files under assigned file code.
6. Log acquisition details in Annexure-3: Spectral Acquisition Log.

5.4 Peak Assignment and Analysis

1. Reference all chemical shifts to the internal solvent peak:
   • CDCl₃: 7.26 ppm
   • DMSO-d₆: 2.50 ppm
   • D₂O: Suppressed
2. Assign each proton signal by:
   • Chemical shift
   • Multiplicity (s, d, t, q, m)
   • Integration (relative number of protons)
   • Coupling constant (J value in Hz)
3. Confirm identity based on expected proton environment and splitting patterns.
4. Use spiking with known standards for confirmation if required.
5. Document peak assignments in Annexure-4: Chemical Shift Assignment Sheet.

5.5 Quantification (if applicable)

1. Use internal standard (e.g., maleic acid, TSP) of known concentration.
2. Ensure that the proton signal of interest does not overlap with impurities or solvent peaks.
3. Calculate concentration using the ratio of integration areas between analyte and internal standard.
4. Document calculation in Annexure-5: Quantification Summary Sheet.

5.6 Data Review and Reporting

1. Compile final method development report including:
   • Sample details
   • Spectral parameters
   • Annotated spectra
   • Peak table and assignment
   • Quantification (if performed)
2. Submit report to QA for review.
3. File raw data, processing files, and final report under controlled document system.

6. Abbreviations

• NMR: Nuclear Magnetic Resonance
• 1H: Proton
• CDCl₃: Deuterated Chloroform
• DMSO-d₆: Deuterated Dimethyl Sulfoxide
• TSP: Trimethylsilylpropanoic Acid

7. Documents

1. NMR Sample Preparation Log – Annexure-1
2. Instrument Setup Log – Annexure-2
3. Spectral Acquisition Log – Annexure-3
4. Chemical Shift Assignment Sheet – Annexure-4
5. Quantification Summary Sheet – Annexure-5

8. References

• ICH Q6A – Specifications: Test Procedures and Acceptance Criteria
• USP <761> – Nuclear Magnetic Resonance Spectroscopy
• Manufacturer’s NMR System User Manual

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: NMR Sample Preparation Log

Sample Name	Solvent	Concentration	Prepared By	Date
API-NMR-001	DMSO-d6	20 mg/mL	Rajesh Kumar	18/05/2025

Annexure-2: Instrument Setup Log

Spectrometer	Field Strength	Solvent	Pulse Program	Temperature
Bruker Avance III	400 MHz	DMSO-d6	zg	298 K

Annexure-3: Spectral Acquisition Log

Sample	No. of Scans	Relaxation Delay	Acq. Time	Comment
API-NMR-001	32	2 s	2.8 s	Good resolution

Annexure-4: Chemical Shift Assignment Sheet

δ (ppm)	Multiplicity	Integration	Assignment
7.26	s	1H	Aromatic proton
2.45	s	3H	Methyl group

Annexure-5: Quantification Summary Sheet

Analyte Signal	Standard Signal	Ratio	Calculated Conc. (mg/mL)
1.25	1.00	1.25	25.0

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Added quantification workflow and annexures	Annual Review