I have to do accuracy and linearity in one run. Linearity is at 0.05% to 2.0% of nominal concentration at five concentration levels and Accuracy is at 0.05%, 1.0% and 2.0% concentration. Accuracy and linearity samples should be in excipient matrix. the question is what should be the excipient concentration? As I did assay validation in which we take excipient conc. same as it is at nominal working conc of active. the excipient conc. remains the same in all samples (at different concentration levels). Sinmce I will be preparing the linearity samples in excipient matrix for the first time. wanted to make sure that excipient conc. does not decrease with th edecreasing conc. of active.

The another question is how do you determine the working conc. of active for related compouds method. Should it be same as the assay active conc.? please advice.