Method validation planning

[gnikol21]

Hello to all
Im working on a product in solution form.
This product exists in 3 different concentrations 20, 40 and 100 mcg/ml.
I have developed HPLC methods for the assay and impurities determination and i'm at the stage of planning the validation procedure of these analytical methods.
The one way is to use the lowest strength of the drug (20 mcg/ml) as working concentration and just dilute the other two strengths into this one.
However i prefer to avoid dilutions and analyze each strength of my product as is (undiluted).
For this reason i have to use different injection volumes to keep the final injected solutions at the same concentration.
My question is: Can i perform one validation which will cover all the three product strengths with adding a linearity using different injection volumes or the only way is to perform one validation for each strength?

Thank you in advance

[gnikol21]

Any suggestion?

[Consumer Products Guy]

The one way is to use the lowest strength of the drug (20 mcg/ml) as working concentration and just dilute the other two strengths into this one.
However i prefer to avoid dilutions and analyze each strength of my product as is (undiluted).

Sounds like your product is a liquid and you want to simply inject as is, or after a filtration. I still think diluting the two higher concentrations to match the lower concentration is easiest way.

For this reason i have to use different injection volumes to keep the final injected solutions at the same concentration.

I do NOT like this approach at all.

My question is: Can i perform one validation which will cover all the three product strengths with adding a linearity using different injection volumes or the only way is to perform one validation for each strength?

I would do linearity over 80-120% of the content for all three products. Then I would do precision and accuracy of the three levels using same HPLC conditions including the same injection volume.

[gnikol21]

Thanks for your answer. I will proceed with the lower strength as working concentration.