Interpret a mass-loss test as its stated loss before calling the entire result water, especially when a formulation contains other volatile components.
Identify the Material Response
Mettler Toledo explains that loss on drying measures evaporated volatile matter and may include constituents besides water. It therefore need not equal a water-specific result. Primary reference: loss on drying and volatile matter.
Review a Hypothetical Comparison
Imagine a fictional 100 g sample loses 5 g in an identified drying method, while a separately validated water determination reports 3 g water on the same initial-mass basis. The numerical difference is 2 g. That discrepancy opens questions about method scope, composition and comparability; it does not prove that exactly 2 g of one particular solvent evaporated.
Keep the Evidence with the Decision
State the temperature/time or endpoint method identity and the mass reference. List known volatile constituents as relevant questions, not guessed corrections. Retain water-assay preparation and matrix suitability beside the comparison. Ask whether the two tests used representative samples and whether reactions or other method effects could also affect the measured difference.
Do not subtract an assumed solvent percentage from every drying result without validated evidence. Conversely, do not reject a useful process loss measurement merely because it is not a water assay; label the quantity correctly for its purpose. The fictional results supply no assay recovery, specification or drying acceptance threshold. They support a method-scope discussion before a powder characterization claim is used in a filling enquiry.
Can a mass-loss result be interpreted as water for the stated formulation?
This blank worksheet is for your own project. It contains no H M machine trial result.
| Review field | Reference or result | Responsible person |
|---|---|---|
| Mass-loss method and endpoint | To complete | To complete |
| Initial mass and reported basis | To complete | To complete |
| Water-assay matrix/preparation | To complete | To complete |
| Other constituents and comparability | To complete | To complete |
Customer Questions
Is every gram lost in drying necessarily water?
No. Other volatile matter may contribute.
Does the fictional 2 g difference identify a solvent?
No. Additional chemical and method evidence is required.
Can loss on drying still be useful?
Yes, when its measured quantity is labelled accurately.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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