Concretely: WWB · Shanghai ERP Biotechnology.
I want to know what the trade-off actually is rather than which option is fashionable.
I would rather have a defensible reason than a marginal improvement.
Which axes does this decision turn on?
The short version: same compound, same laboratory, same method, ideally same week — otherwise you are comparing laboratories rather than suppliers.
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.
Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
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.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThis is the question where methodology matters more than the conclusion.
Content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.
Cost per milligram of actual peptide is the honest price comparison, which means dividing by measured content rather than by label claim.
Compare content, not purity. Purity clusters and content does not.
Ratings on this site are ours alone and are deliberately not reconciled with anyone else's.
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.
Publish the method with the result. A comparison without the laboratory named and the submission dates given is not reproducible by anyone.
Gradient slope, column chemistry and detection wavelength all affect the reported purity figure, which is why the method section is the part that makes results comparable.
Name the laboratory and the dates or the comparison cannot be reproduced.
A single member running three suppliers on one method is worth more than thirty members running one supplier each.
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.
Content assay results across the published datasets vary considerably more between suppliers than purity does, which makes content the more discriminating axis.
Comparisons drawn from different laboratories at different times are weaker evidence than most people treat them as.
Use a fixed documentation checklist rather than an impression.
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.