Read the method before the result. A certificate of analysis is a set of measurements, and a number without its method cannot be compared with another supplier's number. For a peptide such as GHK-Cu (CAS 89030-95-5), start at the top of the document and work down: identity, assay, water, residual solvents, heavy metals, microbial limits, then the signature and the document list. One condition governs everything here: the limits that bind both parties are the ones on the signed batch COA, together with the analytical method agreed before the sample shipped.
Does the certificate describe the right substance?
Check the product name, the registry number and the molecular formula against your purchase specification. For GHK-Cu we expect CAS 89030-95-5 and C14H21CuN6O4; free GHK is CAS 49557-75-7. A mismatch between the title and the number is a reason to pause, not a detail to note later.
Which method produced the assay value?
Ask for the HPLC column, gradient, wavelength and integration rules, and for the basis of the reported value. A result quoted on an as-supplied basis and one quoted on a dried basis differ by the water content. Here is an illustrative calculation: if a 100.0 g sample contains 4.0 g of water, a value of 95.0 on an as-supplied basis becomes about 95.0 / 0.96 = 98.96 on a dried basis. Both numbers describe the same material. These figures are arithmetic examples, not a specification; the point is that the basis must be printed next to the result.
What does an identity trace actually confirm?
An LC-MS or MS trace compared with the theoretical molecular weight confirms that the main peak is consistent with the stated sequence. For GHK-Cu the theoretical value follows from C14H21CuN6O4 at 400.91. Identity and assay answer different questions: one asks what the molecule is, the other asks how much of it is present. A COA that gives only an assay percentage has not answered the first question.
What belongs on a buyer check sheet?
Check: correct substance and registry number, batch number and date, identity method and trace, assay method and calculation basis, water, residual solvents, heavy metals, microbial limits, storage, signature and the document list. What to confirm: which limits were agreed before sampling, which method supports each result, and which documents accompany the commercial shipment.
Why do we publish field names but no results?
Because a catalogue cannot know your batch. Our product pages show the COA structure with empty result columns, so a buyer can see which questions the certificate must answer without being shown a number that belongs to a specific lot. Actual results arrive with the sample and the signed COA.
How do you compare two quotations field by field?
Put both COA field lists side by side and mark any field where the method, the basis or the limit differs. A lower price with an unstated method is not a lower price for the same measurement. Ask each supplier to name the method in writing before comparing numbers.
References
[1] General guidance on certificate-of-analysis content in pharmaceutical quality assurance. [2] General practice for LC-MS identity confirmation and HPLC assay of peptides. [3] CAS Common Chemistry, entry 89030-95-5.
Request the documentation
See our GHK-Cu product page for the COA field list, then email sales@yaxbio.com to request the current COA, MSDS, TDS, a sample or a bulk quotation.