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

https://www.chromforum.org/viewtopic.php?t=5732

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…

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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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