For research use only. Not for human or animal consumption. This article is educational and does not provide medical, dosing, preparation, or application guidance.
Quality and COAs
How to read a COA without getting lost
A certificate of analysis should be read as a batch-specific quality record, not a generic marketing asset.
Written for Procurement, lab operators, and quality reviewers · Updated
Key points
Match product name, batch, task number, lab, testing date, and verification key.
Separate vendor-provided records from VSA BioScience release records.
Confirm measured mass and purity are tied to the exact inventory lot being reviewed.
What 99% purity actually looks like — for research use only.
Research-use boundary
This article is educational and limited to non-clinical research context,
documentation practices, and terminology. It does not provide preparation,
administration, dosing, treatment, diagnostic, cosmetic, or consumer-use
guidance, and nothing here indicates that any material is suitable for human
or animal use.
What a COA is
A certificate of analysis (COA) is a batch-specific quality record from an independent laboratory. It ties a single production lot to its measured purity, confirmed identity, and net content. It is documentation — not a marketing claim. Open the sample certificate above and follow along, section by section.
The header — what you are looking at
Product and lot / batch number: the exact inventory lot the certificate covers.
Accession and search code: the laboratory’s unique file identifier for the report.
Received and reported dates: when the sample reached the lab and when results issued.
Testing laboratory: the independent lab that ran the analysis.
Purity — HPLC-UV
High-performance liquid chromatography separates the sample so each component can be measured; the purity percentage is the share that is the target compound. VSA BioScience holds a ≥99% release floor — a lot that falls below it, or fails, is not released for sale.
Identity — LC-MS
Liquid chromatography–mass spectrometry confirms the molecule’s mass matches the intended sequence. On a passing certificate this line reads “Identity: Confirmed.”
Net content & appearance
Net content is the measured mass in the vial against the labeled amount; appearance describes the lyophilized (freeze-dried) powder. Both should be consistent with the product on file.
Verify it yourself — the QR code
Every vial and report carries a QR code. Scanning it opens the laboratory’s own hosted certificate, so verification comes from the independent lab rather than from us. Always match the lot number printed on the vial to the lot number on the certificate.
Common questions
What is a certificate of analysis for a peptide?
A certificate of analysis, or COA, is a batch-specific quality record issued by an analytical laboratory. It ties a single production lot to its measured purity, its confirmed identity, and its net content. It is a documentation record covering one lot, not a general description of a product line, so a COA from a different lot says nothing about the container in front of you.
What should you check first on a certificate of analysis?
Check that the lot or batch number on the certificate matches the lot number printed on the container itself. Everything else on the document is evidence about that one lot, so if the identifiers do not match, none of the results apply to the material being reviewed. After that, read the header: the laboratory file or accession identifier, the date the sample was received, the date results were reported, and which laboratory ran the analysis.
What does the purity percentage on a COA mean?
High-performance liquid chromatography separates a sample into its components so each can be measured, and the purity percentage is the share of the separated profile attributable to the target compound. It is a measurement made under defined analytical conditions rather than an absolute property of the material, so a purity figure is only interpretable alongside the method that produced it — including the detection wavelength, since an impurity that does not absorb at the wavelength used will not appear in the total.
How does a certificate of analysis confirm identity?
Identity is usually confirmed by liquid chromatography–mass spectrometry, which measures the mass of the molecule and compares it against the mass calculated from the intended sequence. On a passing certificate this line reads that identity was confirmed. A matching mass is strong evidence of elemental composition — it excludes deletions, truncations, most substitutions and oxidation — but composition is a sum, so an intact mass alone does not establish the order of the residues.
What does net content mean on a certificate of analysis?
Net content is the measured mass of material in the container compared against the labelled amount. It is reported separately from purity because a lyophilised solid can also contain residual water, counter-ions and salts, so the mass in the vial is not the same quantity as the mass of peptide in it. Appearance, recorded alongside it, describes the freeze-dried solid and should be consistent with the product on file.
How can a buyer verify a certificate independently?
Ask whether the certificate can be retrieved from the testing laboratory rather than only from the supplier. VSA BioScience prints a QR code on every vial and report that opens the laboratory’s own hosted certificate, so the verification step does not depend on the seller reproducing the document accurately. Match the lot number printed on the vial to the lot number on the retrieved certificate.
What happens to a lot that does not meet its purity specification?
A release specification is only meaningful if failing it has a consequence. VSA BioScience holds a release floor of 99% purity: a lot that falls below that figure on its release certificate, or that fails identity confirmation, is not released for sale. The floor is enforced in the ordering system itself rather than applied by hand at review time.
Why peptide HPLC runs at 214 nm and what 280 nm hidesThe detection wavelength decides what a chromatogram can see. At 280 nm a peptide without tryptophan or tyrosine is close to invisible, and so is an impurity — which is why a purity figure is meaningless without the wavelength attached.
TFA or acetate: why the counter-ion is not inertThe salt form a peptide arrives as changes its weight, and in cell-based work it can change the result. Trifluoroacetate is cytotoxic at nanomolar concentrations, which is well inside the range a peptide stock delivers.
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