A certificate of analysis is the only document that connects the vial on your bench to a measurement someone actually made. Most research-peptide COAs contain the same four elements, and each one answers a different question. This note explains what each element is, what it can and cannot tell you, and the three checks that separate a verifiable certificate from a decorative one.
1. HPLC purity — “how much of what’s in the vial is the peptide?”
Reverse-phase high-performance liquid chromatography separates the components of a sample by hydrophobicity and reports each as a peak. Purity is the area of the main peak divided by the total area of all peaks, usually measured at 214–220 nm where the peptide bond absorbs. A figure of 98.6% means that 98.6% of the UV-absorbing material eluting from the column was the main component.
Three things HPLC purity does not tell you. It does not identify the main peak — a 99% pure sample of the wrong peptide is still 99% pure. It does not measure non-UV-absorbing contaminants such as residual salts, water or trifluoroacetic acid, which is why the peptide content (net weight of peptide per vial) is a separate figure from purity. And the number depends on the method: a short gradient can merge closely eluting impurities into the main peak and inflate the result. A good COA states the column, gradient and wavelength so the result can be reproduced.
2. Mass spectrometry — “is the main peak the right molecule?”
Electrospray or MALDI mass spectrometry measures the mass-to-charge ratio of the sample and is the identity check that HPLC cannot provide. The COA should report an observed mass that matches the theoretical monoisotopic or average mass of the sequence within instrument tolerance — typically well under 1 Da for small peptides. For a peptide like epitalon (theoretical 390.35 g/mol) an observed [M+H]+ of 391.2–391.4 is the expected result; for a longer peptide such as MOTS-c the spectrum will usually show multiply charged ions that deconvolute to the parent mass.
If a COA shows an HPLC trace but no mass spectrum, identity has not been verified. That is the most common gap in this market.
3. Endotoxin — “is the sample contaminated with bacterial material?”
The Limulus amebocyte lysate (LAL) assay detects lipopolysaccharide from Gram-negative bacteria and reports the result in endotoxin units per milligram (EU/mg). It is a cleanliness measure for the synthesis and handling process, not a measure of the peptide itself. It is relevant to cell-culture work because endotoxin activates immune-related signalling in many cell lines and can confound results.
4. Lot number — “does this certificate belong to this vial?”
A COA without a lot number, or with a lot number that does not appear on the vial, is a specification sheet, not a certificate. Peptides are made in batches, and purity varies between batches; a certificate from one lot says nothing about another. The lot number on the vial and the lot number on the certificate must match.
The three checks that matter
Who ran the test? A certificate generated by the manufacturer describes the manufacturer’s own measurement. An independent laboratory’s certificate describes a measurement by someone with no stake in the result. Both have value; they are not interchangeable, and a COA should be clear about which it is.
Can you verify it with the lab? Independent labs that serve this market generally provide a public verification page: enter the report number and the lab’s server returns the result. A QR code or link that resolves to the lab’s own domain is verifiable; a PDF hosted on the vendor’s site is a claim. Be aware that some labs allow the party who paid for the test to keep the report private, so “tested by” and “publicly verifiable” are different statements.
Does the number make sense? Purity above 99.5% on a long, difficult sequence, an observed mass that matches the theoretical value to four decimal places on an instrument that cannot resolve that finely, or identical purity figures across many lots are all reasons to ask questions.
How Alpha Forge Prime documents lots
Each product page shows the HPLC purity and mass-spectrometry identity result for the current lot, with the lot number, and the full certificate set is collected in the COA library for registered account holders. Where a certificate was produced by a third-party laboratory, the report number is shown so it can be checked against the lab’s own records.
Alpha Forge Prime supplies synthetic peptides for in-vitro laboratory research only. Nothing on this page describes or recommends any use in humans or animals. Products are not drugs and have not been evaluated by the FDA.
