What I am working with: SGN · BCH · Norway.
I have used one of these for a while and I am considering switching, which requires a reason.
What I care about is reproducibility, because a result I cannot repeat is not useful to me.
Which axes does this decision turn on?
Answer first: comparing suppliers is only meaningful if the comparison holds the laboratory, the method and the compound constant, and most published comparisons hold none of them.
To compare properly: order the same compound at the same nominal strength from each supplier, submit all samples to the same laboratory in the same submission if possible, and ask for the same test set on each.
In practice, content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.
Content assay results across the published datasets vary considerably more between suppliers than purity does, which makes content the more discriminating axis.
The caveat is that a comparison is a snapshot of the lots compared, and lots change.
One laboratory, one method, one submission. Otherwise it is not a comparison.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe short version: same compound, same laboratory, same method, ideally same week — otherwise you are comparing laboratories rather than suppliers.
Compare documentation on a fixed checklist rather than by impression: lot specificity, method section, chromatogram availability, quantified content, water and counter-ion figures, and whether the code is on the vial.
Cost per milligram of actual peptide is the honest price comparison, which means dividing by measured content rather than by label claim.
Price per milligram of measured peptide, not per milligram of label claim.
edited 26 Jun 2026 by lane_transit — clarified the distinction between purity and content
Start by asking what you are optimising for, because cost per milligram, documentation depth and lead time do not have a common winner.
Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
In practice, publish the method with the result. A comparison without the laboratory named and the submission dates given is not reproducible by anyone.
Comparisons drawn from different laboratories at different times are weaker evidence than most people treat them as.
Name the laboratory and the dates or the comparison cannot be reproduced.
edited 27 May 2026 by tobias_maartens — added the citation requested in comments
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.