Are chromatography/mass spec assays the ideal methods for determining compound purity? [eg for rapamycin or semaglutide]

The thing is, ALL tablets have a lot of binding/filler material, so a chromatography assay of a supplement would have way more than just the supplement itself

Also, multiple compounds can have the same molecular weight. It doesn’t determine whether or not you have the right enantiomer…



like here are lab testing results for semaglutide:

I don’t care about that or microplastics etc since it is a Pascal’s mugging.

In short, no. At least not LCMS as compounds have different ionization potential and so give different detector response for the same amount of material.
Usually purity is checked by LC-UV at a nonspecific wavelength like 220nM. That will at least work for all organic compounds.

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