Osmora Scientific Glossary
Assay
An analytical procedure to measure the presence, amount, or activity of a target substance in a sample; in quality documentation, an assay result often expresses the quantity of the target substance present.
In plain language
A test that measures how much of something is present, or whether it is active.
Why it matters in research
Assay answers a 'how much' or 'how active' question, which is different from the 'what proportion' question purity answers.
Where you'll encounter it
COAs and method descriptions that report quantity or content.
Related terms
Related Academy lessons
Source
- High Performance Liquid Chromatography. Chemistry LibreTexts (Analytical Chemistry). Retrieved 2026.