Audit the documents, the method and the arithmetic before the price. A peptide quotation is only comparable when both suppliers name the same substance, the same analytical method and the same calculation basis. We use a nine-point check sheet and six quote variables for this, and we publish field names rather than results so the audit starts from questions instead of claims. One condition governs the whole process: the binding limits are those on the signed batch COA agreed before a sample ships.
What are the nine checks?
Check, in this order: (1) registry number and INCI name; (2) molecular formula and weight; (3) identity method and trace; (4) assay method and calculation basis; (5) water, residual solvents and heavy metals; (6) microbial limits where the destination market requires them; (7) sample-to-batch traceability and batch numbering; (8) document list, storage and packaging; (9) who signs the COA and who answers a technical question. What to confirm: for each item, which document states it and whether it was agreed before sampling.
Which six variables change a quotation?
Grade and specification, quantity, analytical method and document scope, packaging, destination market and the agreed release limits. A price quoted for one grade with a minimal document pack is not a price for another grade with full reports. Ask the supplier to restate the quote if any of the six changes.
What arithmetic catches a unit error early?
Convert everything to the same basis. Suppose an illustrative quotation offers 100 g at 40 currency units per gram and a second offers 250 g at 36 per gram. The first totals 4,000 and the second 9,000, so the lower unit price costs more in cash. If the first grade needs a 1:10 pre-dilution step that adds 2 hours of technician time per batch, that cost belongs in the comparison too. These are illustrative figures, not our prices or specifications; the point is that unit price alone does not decide a purchase.
How do you verify identity rather than just purity?
Ask for the LC-MS or MS trace against the theoretical molecular weight and the chromatographic conditions used for the assay. For GHK-Cu the theoretical value follows from C14H21CuN6O4 at 400.91; for Acetyl Hexapeptide-8 from C34H60N14O12S at 889. An assay percentage without an identity method has not established what the molecule is.
What should the sample approval record contain?
The sample code, the agreed specification, the analytical method for each field, the trial formula or test result, and the name of the person who approved it. When the first commercial lot arrives, match its COA to that record. If the method changed between sample and bulk, the two results are not comparable.
Which red flags should stop an audit?
A registry number that does not match the product title, a result quoted without a method, a certificate badge with no document behind it, a specification that changes after the sample is approved, or a supplier who cannot name who signs the COA. Each is a documentation problem that will become a receiving problem.
What should you not expect from a catalogue page?
Do not expect a fixed purity figure, a two-year shelf life, a minimum order, guaranteed stock or a lead time. Those are supplier-specific commitments, and we state them per order. What a catalogue should give you is the full identifier block and the list of questions your QA team needs answered.
References
[1] General guidance on supplier qualification and certificate-of-analysis content in pharmaceutical quality assurance. [2] General practice for LC-MS identity confirmation and HPLC assay of peptides. [3] INCI naming convention, Personal Care Products Council.
Request the documentation
Email sales@yaxbio.com with your grade, quantity, destination market and required documents. Ask for a COA, MSDS, TDS, a sample and a bulk quotation; our technical team replies within one business day. You can also browse the GHK-Cu and Acetyl Hexapeptide-8 product pages for the identifier blocks and the COA field list.