[asqa]

differentiate the assay value and purity value.?Compound having 100% purity but assay is 90% only.comment

[kerryh]

"Pure" denotes an undenatured product or a product with a single component as opposed to a mixture. "Purity" refers to the assay or percent composition of the chemical. For example, 190-Proof pure Ethanol has an assay (Purity) of 95% Ethanol and 5% water. This distinction is very important when discussing the critical levels of contaminants and other specifications of chemical products. When referring to the "purity" of a product, it is better to use the term '"assay."


Hope this helps.

[piyush]

dear,
purity means the assay on anhydrous basis where as the assay of the compound is the assay on as is basis.

i hope that this will help.

[asqa]

is it? shall we write purity instead of assay on anhydrous basis.

why then two different terminology?

[Dude]

In the Analytical Chemistry book that I have, an assay is "the process of determining how much of a given sample is the material indicated by the analyte's name."  Therefore, as an example, the toluene sample was assayed for purity by gas chromatography and the purity was determined to be 99 %.  

[asqa]

as per definition it is OK but your example was confusing.

for example i adding 2% w/w water to toluene then i am analysing in GC what the answer i will get 100% assay or 100% purity tell me friend

[Dude]

100 % purity.   Assay is the process or technique (in this example gas chromatography).