For reference: TFC · GGPeps · Ireland.
I would like the axes of comparison first and the recommendation second.
I have tried the first option and it works; the question is whether the second is better rather than merely different.
What is the actual trade-off, and does it matter at the scale I am working at?
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.
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.
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.
Compare content, not purity. Purity clusters and content does not.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsAnswering 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.
In practice, publish the method with the result. A comparison without the laboratory named and the submission dates given is not reproducible by anyone.
The ratings on this site are a community opinion average on a ten-point scale and are not reconciled with any other community's figures.
Nothing here is medical advice, and research-use compounds are not approved for human use.
One laboratory, one method, one submission. Otherwise it is not a comparison.
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.
Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
No supplier on this site pays for its position, and the storefront links are marked nofollow and sponsored.
Name the laboratory and the dates or the comparison cannot be reproduced.
edited 23 May 2025 by t_oyelaran — corrected a unit error in the worked example
Put another way, this 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.
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.
Price per milligram of measured peptide, not per milligram of label claim.
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.