SPE in Pharmaceutical Assay

[lcrandall]

Hello,
Does anyone have experience using SPE for sample clean up of a pharmaceutical complex doseage form?
This would be for drug product release assay, not for any type of biological or plasma/serum type assay.

I can't get a feel of whether SPE cartridges are really meant for the precision that I need for a drug product release assay.
Any thoughts?


Thanks!
Lisa

[Uwe Neue]

The standard approach with SPE is to use an internal standard, preferentially with similar properties as your analyte. Then the precision of the quantitation is not a problem at all.

[lcrandall]

Hello
We did some preliminary work on the internal standard and found one that works well chromatographically.

But, here is the problem...our drug is in both solution and suspension. So, any internal standard that we would use would be added in solution, right? It doesn't seem that we could claim that an internal standard would mimic the behavior of our drug in matrix.

Has anyone encountered that quandry before?

Thanks,
Lisa

[Uwe Neue]

You may have trouble with SPE of a suspension, since the solution is not homogeneous. What can you do to make it homogeneous?