Setup, so nobody has to ask: MKM · HJ · the United States.
The comparison I want does not seem to exist anywhere in a form I can evaluate.
I have read the arguments for each and they do not engage with each other.
So which one, and on what grounds?
The relevant point is that two competent laboratories disagree by half a per cent on identical material, which is larger than most of the differences people argue about.
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.
Content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.
Inter-laboratory spread on identical peptide material is routinely half a per cent to a per cent by RP-HPLC, which is the noise floor for any cross-laboratory comparison.
One laboratory, one method, one submission. Otherwise it is not a comparison.
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemAnswering this needs the axis. A supplier that is best on paperwork and a supplier that is best on price are both correct answers to different questions.
Submitting to different laboratories introduces a method difference that commonly exceeds the supplier difference. Gradient slope alone can move a reported purity figure by a per cent in either direction.
Worth being precise here: cost per milligram of actual peptide is the honest price comparison, which means dividing by measured content rather than by label claim.
Comparisons drawn from different laboratories at different times are weaker evidence than most people treat them as.
Price per milligram of measured peptide, not per milligram of label claim.
edited 18 Aug 2025 by loss_on_drying — reworded for clarity after a comment
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.
Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
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.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Use a fixed documentation checklist rather than an impression.
The relevant detail is that ratings on this site are ours alone and are deliberately not reconciled with anyone else's.
Lead time and lane behaviour are supplier properties too and are easier to compare than analytical ones, because they need no laboratory at all.
The caveat is that a comparison is a snapshot of the lots compared, and lots change.
Name the laboratory and the dates or the comparison cannot be reproduced.
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.