Stated plainly: MKM · Tianjin Finder Chemical.
I am trying to choose between two options that are usually discussed as though only one exists.
I am not optimising for price, but I am not indifferent to it either.
Which axes does this decision turn on?
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.
Content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.
| Step | Value | Note |
|---|---|---|
| Vial price, 10 mg nominal | £34.00 | As advertised |
| Nominal cost per mg | £3.40 | 34 ÷ 10 |
| Measured content | 9.2 mg | Independent content assay |
| Cost per actual mg | £3.70 | 34 ÷ 9.2 |
| Dead-space loss, 20 draws | 4 % | 80 µL of a 2 mL fill |
| Cost per delivered mg | £3.85 | 3.70 ÷ 0.96 |
| First vial, with £110 assay | £14.85 | Testing dominates a single vial |
Lead time and lane behaviour are supplier properties too and are easier to compare than analytical ones, because they need no laboratory at all.
One laboratory, one method, one submission. Otherwise it is not a comparison.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsThe 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.
Mechanically, sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.
Use a fixed documentation checklist rather than an impression.
edited 5 Nov 2025 by ines_brandt — fixed an arithmetic slip in the third paragraph
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.
Cost per milligram of actual peptide is the honest price comparison, which means dividing by measured content rather than by label claim.
On the detail: 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.
Content assay results across the published datasets vary considerably more between suppliers than purity does, which makes content the more discriminating axis.
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.
Publish the method with the result. A comparison without the laboratory named and the submission dates given is not reproducible by anyone.
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.
The honest answer is that most claimed differences between reputable suppliers are inside inter-laboratory noise.
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.
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.
Price per milligram of measured peptide, not per milligram of label claim.
edited 7 Sept 2025 by amara_nwachukwu — reworded for clarity after a comment
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.