Active Pharmaceutical Ingredients (APIs), excipients, and finished pharmaceutical products. It ensures compliance with regulatory guidelines and accurate assessment of moisture content or volatile impurities.

2. Scope

This SOP applies to all solid and semi-solid materials analyzed in the AMD laboratory using gravimetric LOD methods under vacuum or conventional ovens, including hygroscopic and thermolabile compounds.

3. Responsibilities

• Analytical Scientist: Performs method development, conducts trials under specified conditions, and documents data.
• Reviewer: Confirms LOD calculation accuracy and method suitability.
• QA: Reviews and approves LOD method validation report and ensures retention of original records.
• Head – AMD: Oversees the method approval and ensures integration with development dossiers.

4. Accountability

The Head of the AMD department is accountable for ensuring validated LOD methods are available for internal analysis and regulatory submission, and meet pharmacopeial and ICH requirements.

5. Procedure

5.1 Pre-Development Considerations

1. Review literature or pharmacopoeial monographs to understand:
   • Nature of sample (e.g., hygroscopic, volatile, thermolabile)
   • Recommended drying temperature and time
2. Record strategy in Annexure-1: LOD Method Development Plan.

5.2 Equipment Qualification

1. Ensure that the oven (vacuum or convection) is:
   • Calibrated for temperature uniformity
   • Fitted with a certified thermometer or temperature sensor
2. Verify that weighing balances are qualified and within calibration.

5.3 Sample Preparation

1. Weigh 1.0 to 2.0 g of accurately sampled material into a clean, pre-dried, and pre-weighed LOD bottle.
2. Spread uniformly across the base of the bottle.
3. Record gross weight in Annexure-2: LOD Observation Sheet.

5.4 Drying Procedure

1. Place the bottle with open lid in the oven:
   • Temperature: 105°C (default unless otherwise justified)
   • Time: 3 hours (or until constant weight)
   • For vacuum ovens, apply vacuum up to 25 mmHg and heat at 60°C
2. After drying, close the lid and transfer immediately to a desiccator to cool for 30 minutes.
3. Weigh and calculate loss.

5.5 Calculation

LOD (%) = ((Initial Weight - Final Weight) / Initial Weight) × 100

1. Repeat test in duplicate and calculate mean LOD %.
2. Document data in Annexure-2: LOD Observation Sheet.

5.6 Method Optimization

1. Conduct trials at different:
   • Drying temperatures (e.g., 80°C, 105°C)
   • Drying durations (1h, 2h, 3h)
   • Sample weights (1g, 2g)
2. Assess impact on results and endpoint reproducibility.
3. Document all optimization trials in Annexure-3: LOD Optimization Log.

5.7 Method Validation

1. Validation as per ICH Q2(R1):
2. Precision: Six replicates – %RSD ≤ 2%
3. Robustness: Test with minor variations in temperature or time
4. Specificity: Demonstrate that weight loss is solely due to moisture or volatiles
5. Linearity and Accuracy: Not typically applicable for LOD methods
6. Summarize validation results in Annexure-4: Validation Summary Report.

6. Abbreviations

• LOD: Loss on Drying
• AMD: Analytical Method Development
• QA: Quality Assurance
• SOP: Standard Operating Procedure
• ICH: International Council for Harmonisation

7. Documents

1. LOD Method Development Plan – Annexure-1
2. LOD Observation Sheet – Annexure-2
3. LOD Optimization Log – Annexure-3
4. Validation Summary Report – Annexure-4

8. References

• USP <731> – Loss on Drying
• ICH Q2(R1) – Validation of Analytical Procedures
• Ph. Eur., IP – General Tests for LOD
• 21 CFR Part 211 – Laboratory Controls

9. SOP Version

Version: 2.0

10. Approval Section

	Prepared By	Checked By	Approved By
Signature
Date
Name
Designation
Department

11. Annexures

Annexure-1: LOD Method Development Plan

Sample Name	Trial Temp (°C)	Trial Duration (h)	Remarks	Prepared By
API-C	105	3	Stable	Sunita Reddy

Annexure-2: LOD Observation Sheet

Date	Sample	Initial Wt (g)	Final Wt (g)	LOD (%)	Analyst
03/05/2025	API-C	1.002	0.978	2.39	Ajay Mehra

Annexure-3: LOD Optimization Log

Trial No.	Temp (°C)	Time (h)	LOD (%)	Conclusion
1	80	2	1.82	Underestimated
2	105	3	2.39	Optimal

Annexure-4: Validation Summary Report

Parameter	Acceptance Criteria	Result	Status
Precision	RSD ≤ 2%	1.3%	Pass
Specificity	No interference	Confirmed	Pass

Revision History:

Revision Date	Revision No.	Details	Reason	Approved By
04/05/2025	2.0	Added optimization protocol and robustness trial requirements	Audit Compliance