How does WXT compare to Shanghai Sigma-Audley on documentation quality?

The particulars: WXT · Shanghai Sigma-Audley.

I suspect the honest answer is that it depends, in which case I would like to know on what.

Assume I can obtain either option without difficulty, so availability is not the deciding factor.

Under what conditions does the answer flip?

This is the question where methodology matters more than the conclusion.

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.

No supplier on this site pays for its position, and the storefront links are marked nofollow and sponsored.

Price per milligram of measured peptide, not per milligram of label claim.

edited 1 Dec 2024 by tobias_maartens — expanded the table to cover the lower concentration

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.

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.

In practice, lead time and lane behaviour are supplier properties too and are easier to compare than analytical ones, because they need no laboratory at all.

Use a fixed documentation checklist rather than an impression.

edited 31 Dec 2024 by rota_site — removed a claim I could not source

Start by asking what you are optimising for, because cost per milligram, documentation depth and lead time do not have a common winner.

Sample size matters. One order each is an anecdote about six vials; three orders each over a year is the beginning of a comparison.

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.

Specifically, 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.

Name the laboratory and the dates or the comparison cannot be reproduced.

The short version: same compound, same laboratory, same method, ideally same week — otherwise you are comparing laboratories rather than suppliers.

Content is the more discriminating measurement than purity for supplier comparison, because purity clusters tightly among competent suppliers and content does not.

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.

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.