Standard Operating Procedure for Moisture Content Analysis by Loss on Drying (LOD) in API Manufacturing
| Department | API Manufacturing |
|---|---|
| SOP No. | SOP/API/066/2025 |
| Supersedes | SOP/API/066/2022 |
| Page No. | Page 1 of 10 |
| Issue Date | 13/04/2025 |
| Effective Date | 15/04/2025 |
| Review Date | 13/04/2026 |
1. Purpose
To provide a standardized procedure for determining the moisture content in API or intermediate products using the Loss on Drying (LOD) technique to ensure product stability and compliance with specified limits.
2. Scope
This SOP applies to all APIs and intermediates in-process or finished, for which moisture determination is required by LOD method in the Quality Control (QC) laboratory.
3. Responsibilities
- QC Analyst: Perform the LOD test and document results.
- QC Supervisor: Review test data and ensure it meets specifications.
- QA Department: Audit test records and ensure SOP compliance.
4. Accountability
The QC Head is accountable for the accurate execution and reporting of LOD testing. QA Head is responsible for verifying compliance with regulatory standards.
5. Procedure
5.1 Instrument and Materials
- Use calibrated LOD oven or LOD balance capable of maintaining temperature range of 105±2°C unless otherwise specified in monograph.
- Use pre-weighed and clean LOD containers with tight-fitting lids or covers.
- Use desiccator with fresh desiccant for post-drying cooling.
5.2 Sample Preparation
- Weigh 1–2 g of sample (as specified) accurately into a pre-weighed container.
- Record initial weight (W₁) of the container with sample.
5.3 Drying Procedure
- Place the sample container (without cover) in a hot air oven set to 105°C or as specified.
- Dry for a specified time period (e.g., 3 hours or until constant weight is achieved).
- After drying, place the container with lid in a desiccator and allow to cool for 30 minutes.
- Weigh the cooled container and record the final weight (W₂).
5.4 Calculation
- Calculate LOD using the formula:
LOD (%) = ((W₁ – W₂) / Sample Weight) × 100 - Record the value in “LOD Test Log” (Annexure-1).
- Compare the result against the specified limit in BMR or pharmacopeia.
5.5 Acceptance Criteria
- LOD result should meet specification defined in product monograph (e.g., NMT 1.0% w/w).
- If OOS (Out of Specification), inform QC Supervisor and QA for investigation.
5.6 Cleaning and Maintenance
- Clean sample holders and containers after use.
- Ensure oven is cleaned weekly and calibrated as per equipment SOP.
- Maintain cleaning log and calibration records.
6. Abbreviations
- SOP: Standard Operating Procedure
- LOD: Loss on Drying
- QC: Quality Control
- QA: Quality Assurance
- OOS: Out of Specification
7. Documents
- LOD Test Log (Annexure-1)
- Equipment Calibration Record
- Cleaning Log
8. References
- USP <731> Loss on Drying
- ICH Q6A – Specifications
- Internal QC Guidelines
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 Test Log
| Date | Batch No. | Sample Weight (g) | W₁ (g) | W₂ (g) | LOD (%) | Analyst |
|---|---|---|---|---|---|---|
| 13/04/2025 | API-20250413 | 1.00 | 4.00 | 3.98 | 2.00 |
Revision History:
| Revision Date | Revision No. | Details | Reason | Approved By |
|---|---|---|---|---|
| 01/01/2022 | 1.0 | Initial SOP Release | Standard Method Implementation | QA Head |
| 13/04/2025 | 2.0 | Updated with Desiccation, Cleaning, and OOS Procedure | Audit Recommendation | QA Head |