# Calculate the Potancy of Working standard

Dear All,

please guide me How to Calculate potancy of Working Standard ?
For Example Assay As is Basis = 98.5%
Water Content = 1.25%
Rel.Substances = 0.15%
Residue on ignition= 0.02%
Residual solvents = 100 ppm

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Your question is not clear. As per my understanding,

“Potency” is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity.
“Potency” is defined as “the specific ability or capacity of the product, as indicated by appropriate laboratory tests or by adequately controlled clinical data obtained through the administration of the product in the manner intended, to effect a given result.”

“Purity” is a measure of the amount of API present in a sample compared to those of related substances, impurities, residual solvents, etc.

Therefore, the term potency should be used in relation to the biological activity. However, the terms potency and Assay / purity are used interchangeably many times.

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Assay on AS IS BASIS is Potency in that case

Probably yes.
However, terms Potency and Assay are technically different. For example, if a specific chemical compound is 100% pure (Assay) but may not have 100% potency (expected biological / clinical activity).

Working standard qualified against primary reference standard.
Reference standard are available from US pharmacopoeia or European pharmacopoeia as per your market requirement.
Simply performed assay against reference standard and calculate Potency .

For Example
Assay is 99.5% on dried or anhydrous basis
water content or Loss on Drying is 0.5 % of API
calculate Potency (100-0.5)*99.5/100
Potency as such = 99.0%

When you have assay on dried basis 99.5%. How you are getting again 0.5% water.
Assay should be on as is basis.

Dear Sajid,

Assay calculate on two type, one is as is basis (w/o water correction) and on dried basis.

Generally as per Pharmacopoeias monograph they have mentioned assay calculate On dried basis (ODB) means with content of water.

For Example : Assay limit is 98.0 to 100.0% on dried basis. Water content is 1.0% w/w

Our assay results is 99.5% on dried and water content results is 0.5%

If you calculate assay on as is basis, should must require correction of water content.

So on as basis calculation = Assay on dried basis X (100 – Water content)
100

``````                                               = 99.5 X (100 – 0.5)
100

= 99.0% on as is basis
``````

Further you have any query let me know