Assay for Testing of Pharmaceutical Raw materials

Often in the USP and BP, the same method is used for assay and related substance/impurity testing.

We currently do no perform the related impurity tests routinely. It is taken for the supplier COA.

Can anyone explain the need for a resolution standard if only the assay is performed. eg. Nevirapine USP, the same method is used for assay and related substance/impurity testing. It requires a resolution solutions to perform the assay and impurities. These stds are impurity std and are very expensive. Is it necessary to run the resolution solution to check system suitability everytime we perform the assay only. I understand that it will be required when testing of related subst/impurities where we want to ensure that the method can adequately separate and quantify the impurities.

Our QA dept insists that this is necessary. I do not see the value adding if the expected resolution is more than 2, say 5.


I think being an analyst you must not bother about cost of these standards.Its not your job function.

Secondly what your QA insisting is very correct.

According to ICH guidelines,1 impurities associated with APIs are classified into the following categories:

Organic impurities (Process and Drug-related)
Inorganic impurities
Residual solvents

Organic impurities may arise during the manufacturing process and/or storage of the drug substance. They may be identified or unidentified, volatile or non-volatile, and include the following: Starting materials or intermediates- These are the most common impurities found in every API unless a proper care is taken in every step involved inthroughout the multi-step synthesis. Although the end products are always washed with solvents, there are always chances of having the residual unreacted starting materials may remain unless the manufacturers are very careful about the impurities.

I want ask you a question: How good is your Raw material Supplier Qualification Protocol?

Do you always take only from a Qualified Vendor?

Did you check his batch to batch variation?

You will be the best judge now if you can reply these questions.

We all must know , believe and function to ensure and assure that nowhere the Product quality is compromised during Production , Processing ,Analysis and Assurance.