The Loss on Drying (LOD) test is a classic analytical technique used to determine the amount of volatile matter—including water and residual solvents—present in a sample. Unlike more specific tests (like Karl Fischer titration, which only measures water), LOD measures any mass lost when a sample is heated or dried under specific conditions.
Test Principle & Procedure
The principle is simple: Thermogravimetric analysis. You measure the mass of a sample before and after a drying process; the difference is the " Loss on Drying," typically expressed as a percentage.
Standard Procedure (e.g., USP<731>):
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Applicable Industries
LOD is a foundational quality control test across several sectors:
- Pharmaceuticals: Ensuring active ingredients (APIs) and excipients meet stability and dosage standards.
- Food & Agriculture: Measuring moisture in grains, flour, and dried spices to prevent spoilage and ensure "fair weight" in trade.
- Chemicals: Testing polymers, resins, and fine chemicals for residual solvents.
- Cosmetics: Controlling the consistency and shelf-life of powders and creams.
Standards & Referencing Documents
Global regulatory bodies provide strict guidelines to ensure reproducibility:
Authority | Reference | Focus |
| USP (United States Pharmacopeia) | Chapter <731> | Gold standard for pharma; defines "dry to constant weight." |
| EP (European Pharmacopoeia) | Chapter 2.2.32 | Similar to USP; used across Europe for drug substances. |
| ASTM International | ASTM E1868 | Standard for LOD by Thermogravimetry (industrial/chemical). |
| ASTM International | ASTM E1131 | Compositional analysis of solids/liquids by Thermogravimetry. |
| AOAC International | Official Methods | Specific procedures for various food products (e.g., meat, dairy). |
| ISO | ISO 11465 | Soil quality and moisture content determination. |