An assay is a laboratory procedure that identifies or measures a specific substance in a sample. Whether it’s checking how much of a drug is in a tablet, detecting bacteria on a kitchen surface, or measuring hormone levels in your blood, the underlying process is an assay. Assays are performed to establish the metal content in samples taken from the rock. About 24 hours before assay the sample was placed in 80% ethanol. ASSAY definition: 1. to examine a substance to find out how pure it is or what its properties (= qualities) are: 2…. Learn more. An assay is a breakdown of a material, examining the individual parts that make up the whole. When you assay a situation, you look at all the elements that created the problem in order to come up with a solution. As a noun, assay means a test or appraisal to determine the components of a substance or object. As a verb, it refers to the act of analyzing, or of conducting that test. It is usually used in chemistry-related fields like metallurgy and pharmaceuticals, but you can also assay a poem. An assay is an investigative (analytic) 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. The meaning of ASSAY is to analyze (something, such as an ore) for one or more specific components. How to use assay in a sentence. Did you know? 1. to examine or analyze: to assay a situation. 2. to analyze (an ore, alloy, etc.) to determine the content of gold, silver, or other metal. 3. to analyze (a drug) to determine potency or composition. 4. to test or evaluate: to assay one's strength. 5. to attempt; try; essay: to assay a dance step. n. An assay is a laboratory procedure or test that is performed to determine the presence, concentration, quality, or biological activity of a specific substance or component within a sample. determination of the purity of a substance or the amount of any particular constituent of a mixture. biological assay bioassay; determination of the potency of a drug or other substance by comparing the effects it has on animals with those of a reference standard.