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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?
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.
Publish the method with the result. A comparison without the laboratory named and the submission dates given is not reproducible by anyone.
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.
Name the laboratory and the dates or the comparison cannot be reproduced.
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 BiochemWorth being precise here: ratings on this site are ours alone and are deliberately not reconciled with anyone else's.
Content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.
To be exact about it, lead time and lane behaviour are supplier properties too and are easier to compare than analytical ones, because they need no laboratory at all.
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.
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.
Answering 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.
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.
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.
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One laboratory, one method, one submission. Otherwise it is not a comparison.
edited 29 Oct 2024 by plate_count_9k — added the citation requested in comments
The short version: same compound, same laboratory, same method, ideally same week — otherwise you are comparing laboratories rather than suppliers.
Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
Content assay results across the published datasets vary considerably more between suppliers than purity does, which makes content the more discriminating axis.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Price per milligram of measured peptide, not per milligram of label claim.
edited 1 Jul 2024 by forty_two_c — 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.
Cost per milligram of actual peptide is the honest price comparison, which means dividing by measured content rather than by label claim.
The caveat is that a comparison is a snapshot of the lots compared, and lots change.
Compare content, not purity. Purity clusters and content does not.
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.