Second pass at: Why this subcategory is stricter about sourcing than most

A mass result for a short peptide is more discriminating than for a long one, because a single residue difference is a larger proportion of the total. That makes identity confirmation genuinely useful here.

Following, with nothing to contribute beyond having asked the same thing elsewhere.

That is a fair summary of where the discussion has got to.

Why this subcategory is stricter about sourcing than most: the evidence base is weaker and that is precisely why documentation quality matters more. A supplier page that clearly identifies the compound and the purity is more valuable for secretagogues than for incretin agonists where the evidence base is stronger.

Reconstitution volumes in this family are often small enough that dead volume in the syringe is a meaningful fraction of the dose. A fixed-needle insulin syringe is worth the trouble here specifically.

The uncertainty is in the assumption, not in the calculation.

This is the sort of exchange that makes the archive worth searching.

Where I part company with post #50, and it is a narrow parting.

On analysis: these are short peptides and generally straightforward chromatographically, which means a poor purity result is more likely to reflect the synthesis than the method.

Adding a source would improve this post and I do not have one to hand.

Post #56 is right about the mechanism and I think understates the practical bit.

Storage: these are lyophilised short peptides and are generally reasonably stable dry and considerably less so in solution. Reconstituting only what will be used within the period the supplier's own data covers is the conservative approach.

A mass result for a short peptide is more discriminating than for a long one, because a single residue difference is a larger proportion of the total. That makes identity confirmation genuinely useful here.

Caveat: everything above assumes the paperwork is what it says it is.