validation required following increase in injection volume?

[mojo]

We hope to be using a USP assay method which has an injection volume of 10 uL. However, our potential product has a fairly high ratio of excipient to active, so we may need to dilute our samples more than the USP method (the USP method is not dose specific). To account for this we would like to increase injection volume by as much as 50 uL. What validation would be required for such an increase? The amount of active being injected would be the same as the USP method, just a greater injection volume would be used.

[Consumer Products Guy]

I'm not sure that diluting more and injecting more gets you anywhere, unless your orginal concentration was too viscous. Your excipient to active ration stays the same. 50 ul is a lot, but if your solvent is weaker than mobile phase, might not hurt you. What I'd do would be to assay some samples both ways, and if results aren't affected, write a memo for the cGMP file.

[mojo]

Hi,

If we were to follow the USP method, we would end up adding 0.625 mL of diluting solution to our 90 mg tablet! Hence, the desire to have an increased sample volume.