A quantitative or qualitative test of a substance (especially an ore or a drug) to determine its components; frequently used to test for the presence or concentration of infectious agents or antibodies etc. WordNet 3.0 & Open English WordNet

An assay is an investigative procedure in laboratory medicine, mining, pharmacology, environmental biology and molecular biology for qualitatively assessing or quantitatively measuring the presence, amount, or functional activity of a target entity. Wikipedia

Investigative procedure in laboratory chemistry, medicine, pharmacology, environmental biology and molecular biology Wikidata

Qualitative or quantitative determination of the components of a material, such as an ore or a drug. OmegaWiki

The qualitative or quantitative chemical analysis of something. Wiktionary