I'm required to do the precision of the method and perfoming the precision with sample , by spiking known amount of impurity up to specification limit to the main compound. Is this way correctr?. Or Do I have to get the sample prepared in the laboratory to contain the required impurity at specificewd level and then perfom on such sample. Can anybody suggest me.

I hope your question is related to the validation of Related substances method. For precision of method, it is sufficient to show data from different sample preparations. (eg. 6 different weights). Spiking of impurity or any special sample preparation containing impurities is not required.

Do the precision at the specification limit is not required?

pds:

What is your question?

Performing the precision at the specification limit is not required?

What do you mean by specification limit?

Please clarify your question so we can help.

Sir,

I mean , if the specification limit for certain impurity-1 is 0.5% (say), impurity-2 is 0.1%(say) and my sample contain the impurity-1 at 0.2% only and no impurity-2.
Then , the precision conducted will be for impurity-1 at 0.2% and not being for impurity-2.

So, I do not know the precision of the method at the spec limit of 0.5% and 0.1% respectively.

Hope u understand my question in this way.

pl. help.

Is the method written (and being validated) to analysis both impurity 1 and impurity 2? If the answer is yes, then you would have to perform precision for both impurities. If the answer is no, then you would only have to do precision for impurity 1. I hope this clarifies things for you.

P.S. Don't assume we are all Sirs. :)

OK
But, do we need to spike the material or not.

From my opinion you can do the precision at any concentration between quantification limit and specification limit. If your impurity is not found in the sample, it should be added either by spiking or mixing.

Is the spiking of the sample is acceptable. Because , in our regular analysis the sample preparation doesnot contain any spiking , where as in the validation the precision is being done by spiking a sample which is not a part of method.

Can you pl elaborate me.

Is it true that with your normal sample preparation you may or may not see the impurtiy peak depending upon the stability of the primary analyte? When performing a validation you have to spike known quantitites of the impurtiy so you know that it is detectable under your methods conditions.