Assay
The measured content of the named substance in a sample, normally expressed as a percentage by weight. It may be determined by titration, HPLC, GC or another validated method, and is often calculated on the dried or anhydrous basis so that water does not distort the figure. Assay states how much of the main component is present but says nothing on its own about which impurities make up the rest.
Related terms
Certificate of Analysis (COA)
A document issued for a specific lot that lists each specification test, its acceptance limit and the result…
HPLC
High-performance liquid chromatography separates compounds dissolved in a liquid mobile phase as they pass th…
Loss on Drying (LOD)
A test that measures the percentage of weight a sample loses when heated under defined conditions of temperat…
Reference Standard
A highly characterised material used as a benchmark to confirm identity, measure assay or quantify impurities…
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