What is the difference between assay and analysis?

Answer 1

Assay is the quantitative determination of the amount of a component in a sample.

Purity is the determination of the impurities in the sample. It can be quantitative, semi-quantitative or qualitative.

For example : if you dissolve 4 grams of compound A (with no impurities in it) in 6 grams of water, you get a solution of compound A with 100% purity and 40% assay.

From the ICH Guideline Q2A (Validation of Analytical methods) :

"- Testing for impurities can be either a quantitative test or a limit test for the impurity in a sample. Either test is intended to accurately reflect the purity characteristics of the sample. [...]

- Assay procedures are intended to measure the analyte present in a given sample. In the context of this document, the assay represents a quantitative measurement of the major component(s) in the drug substance."

Answer 2

Potency is a measure of the activity of a drug in a biological system & assay is analysis of drug to determine the presence, absence, or quantity of one or more components. A purity test is to ensure that all the analytical procedures performed allow an accurate statement of the content of impurities of an analyte, i.e. related substances test, heavy metals, residual solvents content, etc. Assay: to provide an exact result which allows an accurate statement on the content or potency of the analyte in a sample. u can find answer in International conference on Harmonisation(ICH)(2005) online edition:)

Answer 3

Assay is to get the result, and the analysis is to go with the result or understanding the result.