Lab and analysis
Impurity profile (related substances)
Definition
The identity and amount of impurities in a material, often measured by HPLC as related substances.
For APIs and fine chemicals the impurity profile matters as much as purity. Specifications usually limit any single known impurity, any unknown impurity and total impurities. ICH guidelines set thresholds for reporting, identifying and qualifying impurities in new drug substances.
A change in route of synthesis can change the impurity profile even when the purity stays the same, so buyers in regulated industries expect to be told about process changes.
Related terms
- HPLCHigh performance liquid chromatography, the most common method for assay and impurity testing of organic chemicals and APIs.
- Residual solventsTraces of process solvents left in a product, limited for pharmaceuticals by ICH Q3C.
- Elemental impuritiesTrace metals and other elements in a product, controlled for medicines by ICH Q3D.
- PurityHow much of a material is the stated substance, usually given as a percentage and measured by a defined method.