Lab and analysis
Assay
Definition
A quantitative test for the content of the main substance, and the result of that test on a certificate of analysis.
Assay methods include titration, HPLC, GC and spectroscopy. Pharmacopoeia monographs specify the method and limits, often as a range such as 98.0 to 102.0 percent on the dried or anhydrous basis.
An assay above 100 percent is possible within method uncertainty or when the result is calculated on a dried basis. Values far outside the expected range are a reason to ask questions.
Related terms
- COA (certificate of analysis)A batch specific quality document listing the tests performed, the specification limits and the actual results.
- SpecificationThe list of tests, methods and acceptance limits a product must meet, agreed between supplier and buyer or set by a standard.
- PurityHow much of a material is the stated substance, usually given as a percentage and measured by a defined method.
- Batch number (lot number)A code that identifies a quantity of product made in one production run, used for traceability.