Conditions: GGPeps · Homopeptide · Canada.
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 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.
Stated carefully, lead time and lane behaviour are supplier properties too and are easier to compare than analytical ones, because they need no laboratory at all.
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.
Name the laboratory and the dates or the comparison cannot be reproduced.
edited 7 Dec 2024 by tobias_maartens — added a caveat about sampling
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe honest answer is that most claimed differences between reputable suppliers are inside inter-laboratory noise.
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.
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.
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.