At our lab we have a method that has to be validated. The method is an HPLC assay determination of one API in 10 different formulations.
(e.g. Raw material, 100% formulation, 20% API in lactose, or combined with another API(s)).
The method is used for several years at our laboratory, and there are no problems with interfering peaks of other API’s / excipients.
What has to be validated for the method?
Is it necessary to perform the validation for each formulation?
Is necessary to perform robustness/accuracy/precision for each formulation?
Or is it sufficient to test the specificity using spiked formulations?
I’m not an expert, but in our laboratory we would do as one validation, and one reference standard concentration. In other words, one linearity, one robustness study, etc. I’d start with the sample preparation of the most complex formulation, which would be the lower level in presence of other “stuff”. Then your higher and purer samples would be prepared at equivalent concentrations.
We’d examine all 10 formulations (with placebo formulations) for specificity, and also spike such placebo formulations for the accuracy piece. Then the HPLC part remains the same for all, just the dilution is greater or less weighed for purer samples.