Definition

Loss on Drying is a back-weighing application used to determine the amount of volatile matter (such as water or solvents) present in tablets, capsules, or bulky materials.

Common Methods

In a Desiccator: Drying over Phosphorus pentoxide at atmospheric pressure.

“In Vacuo”: Drying over Phosphorus pentoxide at a specific pressure (1.5 kPa to 2.5 kPa).

In an Oven: Carried out within a specified temperature range prescribed in a monograph.

General Procedure Highlights

Sample Weight: Generally 1 to 2 g unless specified otherwise by a monograph.

Sample Depth: About 5 mm, or not more than 10 mm for low bulk density materials.

Constant Weight: Drying continues until two consecutive weighings do not differ by more than 0.50 mg/g (USP) or 0.5 mg (European Pharmacopoeia).