Reference Guide · Updated August 20, 2026
How to Read a Peptide Certificate of Analysis
A COA is the only document that ties a number to the vial in your hand. This guide covers what each field actually proves, what it does not, and the red flags that make a confident-looking report worth less than it appears.
The short answer
Check the lot number first and confirm it matches your vial — a COA without a matching lot proves nothing about your material. Then read three numbers together: HPLC purity (how clean the main peak is), mass spectrometry identity (whether it is the right compound), and net peptide content (how much of the vial mass is actually peptide). Purity and net content are different measurements, and the gap between them is where most misreadings happen.
Field by field
Product name & sequence
Which compound the document is about, usually with the one-letter or three-letter amino-acid sequence and a molecular formula.
Watch for: The sequence should match the compound you ordered. A COA with a product name but no sequence is weaker evidence than one that prints it.
Lot / batch number
That the results belong to one specific production run — not to the product line in general.
Watch for: This is the field that makes a COA meaningful. It must match the lot printed on the vial you received. A COA with no lot number proves nothing about your material.
Purity by HPLC (%)
The share of total UV-absorbing peak area attributable to the main peak in reversed-phase high-performance liquid chromatography.
Watch for: Purity is a ratio of peaks, not a measure of how much peptide is in the vial. A 99% pure peptide can still be well under 99% peptide by mass — see net peptide content below.
Identity by mass spectrometry
That the observed molecular mass matches the theoretical mass calculated from the sequence, confirming the compound is what the label says.
Watch for: Look for both the theoretical and the observed mass. Reporting only "conforms" or "pass" without numbers is a weaker claim than printing the measured value.
Net peptide content (%)
How much of the vial’s mass is actually peptide, once counter-ions, residual water and salts are excluded. Usually measured by amino-acid analysis or nitrogen determination.
Watch for: This is the number most often missing, and the one that most changes what you are actually buying. Typical trifluoroacetate salt forms run roughly 70–85% net peptide even at 99% chromatographic purity.
Water / moisture content
Residual water left after lyophilization, usually by Karl Fischer titration or loss on drying.
Watch for: High residual moisture shortens shelf life. It also inflates apparent mass, which matters when the vial is sold by weight.
Appearance
The physical form and colour of the lyophilized material — normally a white to off-white powder or cake.
Watch for: Worth comparing against what arrives. Discolouration or a collapsed cake can indicate a handling or storage problem in transit.
Endotoxin (EU/mg)
Bacterial endotoxin load, typically by LAL assay. Relevant for cell-culture work, where endotoxin confounds results at very low concentrations.
Watch for: Only present if the assay was actually run. Many research-grade COAs omit it entirely — absence is not a failing grade, but it is not a pass either.
Test date & analyst / laboratory
When the analysis was performed and who performed it.
Watch for: A COA dated years before your lot was packaged is describing different material. An independent third-party laboratory named on the document carries more weight than an unattributed in-house report.
Storage & handling statement
The conditions under which the stated specifications are expected to hold.
Watch for: Specifications describe the material as tested. Storage outside the stated conditions is outside what the document covers.
Red flags
- No lot number, or a lot number that does not match the vial. The single most important check, and the easiest to skip.
- A purity figure with no chromatogram behind it. A number typed into a template is not the same as data.
- Identity reported as "conforms" with no observed mass printed alongside the theoretical mass.
- The same COA supplied for every lot of a product. If the document never changes, it is a brochure, not an analysis.
- Assays listed in marketing copy that do not appear on the actual report — for example a site claiming every batch is heavy-metal tested when the COA shows no such assay.
- A test date that predates the production date of the lot in your hand.
Frequently asked
What is a peptide Certificate of Analysis?
A Certificate of Analysis is a laboratory document reporting the measured specifications of one specific production lot of a peptide — most importantly its chromatographic purity and its confirmed identity. It is the primary evidence of what is actually in a given vial, as distinct from what the label claims.
How do you read a peptide COA?
Start with the lot number and confirm it matches the vial. Then read purity by HPLC, identity by mass spectrometry, and net peptide content together — purity is a ratio of chromatographic peaks, identity confirms the compound, and net peptide content tells you how much peptide the vial actually holds. Finally check the test date and the laboratory named on the report.
Is 99% purity the same as 99% peptide?
No. HPLC purity describes the proportion of total peak area belonging to the main peak. Net peptide content describes what share of the vial mass is peptide once counter-ions, salts and residual water are excluded. A peptide can be 99% pure by HPLC and still be substantially less than 99% peptide by mass.
What does HPLC measure on a peptide COA?
Reversed-phase HPLC separates the components of a sample and measures the UV absorbance of each as it elutes. The reported purity figure is the area of the main peak as a percentage of total integrated peak area. It answers how clean the material is relative to other UV-absorbing species, not how concentrated it is.
Does a COA need to be from a third-party lab?
Not by rule, but an independent laboratory named on the document removes the obvious conflict of interest in a manufacturer grading its own work. Third-party attribution, a printed lot number and visible underlying data are the three things that most raise the evidential value of a COA.
What should a COA never be used for?
A COA characterises material. It says nothing about safety, suitability or use in humans or animals. Research peptides are laboratory reference materials only, and analytical documentation does not change that.
Go deeper
- How to Read a Peptide COA — The long-form walkthrough with cited sources.
- HPLC vs Mass Spectrometry — Why the two tests answer different questions.
- Net Peptide Content vs Purity — Two numbers routinely mistaken for each other.
- Peptide Endotoxin Testing — What EU/mg means and when it matters.
- Why Third-Party Testing Matters — Independent attribution and what it is worth.
- Lyophilized Peptides Explained — Freeze-drying, residual moisture and stability.
- Storage Best Practices — Keeping material within its tested specification.
- Reconstitution Guide — Laboratory handling once the vial is opened.
Our documentation
Every Dynamite Research Peptides compound is supplied with batch documentation available on request. See our testing and quality standards, the supplier evaluation checklist, or browse the research catalog.
This article is informational and for research purposes only; it is not medical, veterinary, or dosing advice, and makes no claim about the treatment of any condition. All products are sold strictly as research reference material for in-vitro laboratory research use only — not for human or veterinary use, and not FDA-approved for any medical use.