How to Read a Peptide Certificate of Analysis (COA): A Step-by-Step Guide

For research use only. Not for human or veterinary use.

By Courtney Barber | Published October 28, 2026

Quick answer: A peptide Certificate of Analysis (COA) is a report from a testing laboratory about one specific batch of material. When you read it, check five things. First, the report identifies the right compound and batch. Second, the identity test (usually mass spectrometry) matches the expected molecular weight. Third, the purity result (usually HPLC) is stated with its method. Fourth, the report is recent and comes from a named laboratory. Fifth, the report can be verified directly with the lab that issued it.

Researchers depend on documentation to trust their reagents. This guide explains each section of a typical third-party peptide COA, what the numbers mean and don’t mean, and how to confirm a report is genuine. You can follow along with any report in the QC Labs COA Library, where COAs are available for each listed batch.

What is a Certificate of Analysis for a research peptide?

A COA is a lab report that documents analytical test results for a specific sample from a specific batch or lot. It is not a general statement about a product line. A COA for one lot tells you nothing about a different lot, so always match the batch or lot identifier on the COA to the material you have.

For research peptides, third-party COAs usually report:

• Identity: Is this the expected molecule? Usually checked by mass spectrometry (MS or LC-MS).
• Purity: What fraction of the detected peptide signal is the target peptide? Usually measured by reversed-phase HPLC with UV detection.
• Quantity or content (sometimes): How much peptide is in the vial, compared with the labeled amount.

Some reports also include extra tests such as endotoxin, residual solvents, or counter-ion content. If a test isn’t on the COA, it wasn’t reported. Don’t assume it was done.

Section 1: Header information (who, what, when)

Start at the top of the report and check:

• Laboratory name and contact: A real, independently verifiable lab (for example, Janoshik Analytical or Freedom Diagnostics Testing).
• Client / sample submitter: Who submitted the sample.
• Sample name: The compound and labeled amount (e.g., “BPC-157 10 mg”).
• Batch / lot number: Must match the batch identifier on the product listing or vial label.
• Dates: When the sample was received and when it was tested or reported.
• Report ID / task number / accession number: The identifier you use to verify the report with the lab.

If any of these are missing or blurred, treat the report with caution.

Section 2: Identity results (mass spectrometry)

What it tells you: Mass spectrometry measures the mass-to-charge ratio of ionized molecules. Electrospray ionization, the soft-ionization technique that made MS practical for large biomolecules like peptides, was described by Fenn and colleagues in Science in 1989 (PubMed 2675315).

How to read it: Compare the observed mass with the theoretical (expected) mass for the peptide’s sequence. Peptides often show several charge states (for example [M+2H]²⁺ or [M+3H]³⁺), so the report may list more than one m/z value or a deconvoluted mass. A close match supports identity. A large mismatch suggests a different or modified molecule.

What it doesn’t tell you: A correct mass confirms that the target molecule is present. It doesn’t, on its own, tell you how pure the sample is.

Section 3: Purity results (HPLC)

What it tells you: HPLC purity is usually reported as area percent: the target peptide peak’s area divided by the total area of all integrated peaks at a given UV wavelength (often 214–220 nm for peptide bonds). A 2022 review describes how chromatographic methods are developed and validated for characterizing synthetic peptides (Sharma et al., J Sep Sci, PubMed 35460196).

How to read it:

• Look for the chromatogram image: one dominant peak, with any smaller impurity peaks labeled or integrated.
• Note the method details if given (column, gradient, wavelength). Purity values from different methods aren’t always directly comparable.
• The impurities in synthetic peptides are often closely related to the target, such as deletion sequences, truncations, incomplete deprotection, or oxidation and deamidation products. These are reviewed in D’Hondt et al., “Related impurities in peptide medicines,” J Pharm Biomed Anal 2014 (PubMed 25044089).

What it doesn’t tell you: HPLC area percent is relative purity among UV-absorbing species. It doesn’t measure water, salts, or counter-ions, and it doesn’t measure total peptide mass in the vial.

Section 4: Quantity, content, and counter-ions

Some COAs report a measured quantity (e.g., “10.2 mg found”). This differs from purity: a sample can have high HPLC purity and still contain less or more peptide than labeled.

Synthetic peptides purified by reversed-phase HPLC are commonly isolated as trifluoroacetate (TFA) salts. Counter-ions and residual water add weight without adding peptide. A 2025 review discusses how TFA is analyzed and exchanged in synthetic peptides (Erckes et al., Pharmaceuticals, PubMed 40872554). If a COA doesn’t report content or counter-ion data, don’t infer them from the purity number.

Section 5: How to verify a COA with the issuing lab

A real third-party COA can be checked against the lab’s own records:

• Janoshik Analytical: Go to the official verification page (janoshik.com/verification). Enter the task number and the unique key printed on the report, and check that every returned value matches the COA you’re holding.
• Freedom Diagnostics Testing: Use the lab’s COA lookup by accession number or search code (Freedom Diagnostics COA lookup) and compare the returned PDF with your copy.

Red flags:

• No verification code.
• The lab’s record doesn’t match the COA (different compound, date, or values).
• Signs of editing in the PDF.
• The batch number on the COA doesn’t match your material.

Our Quality Verification page walks through this process for QC Labs batches.

Common COA misreadings to avoid

• “99% purity” means 99% of the vial is peptide. No. HPLC purity is relative peak area, not mass content.
• One COA covers every batch. No. A COA applies only to the batch tested. That’s why QC Labs posts COAs for each listed batch rather than one report per product.
• Correct mass means pure. No. Identity and purity are separate questions. See HPLC vs. Mass Spectrometry.
• An old COA is still current. Peptides can degrade over time, so test dates matter. See Lyophilized Peptide Storage and Handling.

COA reading checklist

• Lab name is independent and verifiable
• Compound name and labeled amount match
• Batch or lot number matches your material
• Test date is recent and plausible
• MS observed mass matches the theoretical mass
• HPLC chromatogram is shown, with purity and method
• Any additional tests (content, endotoxin, etc.) are clearly labeled
• Report verified on the issuing lab’s website

Frequently asked questions

What does COA stand for in peptides?

Certificate of Analysis. It’s a lab report documenting test results (typically identity and purity) for a specific batch of a peptide.

Is HPLC purity the same as peptide content?

No. HPLC purity is the relative area of the target peak among detected peaks. Content (or net peptide content) refers to how much of the material’s mass is actually peptide, as opposed to water, salts, or counter-ions.

How can I tell if a peptide COA is fake?

Verify it directly with the issuing lab using the report’s verification code or accession number. Then confirm that the compound, batch, dates and values match exactly.

Does a COA guarantee a product is safe for human use?

No. A COA is an analytical report for research material. QC Labs products are for research use only and are not for human consumption.

Where are QC Labs COAs?

In the QC Labs COA Library. COAs are available for each listed batch. You can browse research materials in the shop and find policy answers in the FAQ.

References

• Fenn JB, et al. Electrospray ionization for mass spectrometry of large biomolecules. Science. 1989. https://pubmed.ncbi.nlm.nih.gov/2675315/
• Sharma N, et al. Synthetic pharmaceutical peptides characterization by chromatography principles and method development. J Sep Sci. 2022. https://pubmed.ncbi.nlm.nih.gov/35460196/
• D’Hondt M, et al. Related impurities in peptide medicines. J Pharm Biomed Anal. 2014. https://pubmed.ncbi.nlm.nih.gov/25044089/
• Erckes V, et al. Towards a consensus for the analysis and exchange of TFA as a counterion in synthetic peptides. Pharmaceuticals (Basel). 2025. https://pubmed.ncbi.nlm.nih.gov/40872554/
• Janoshik Analytical, Verification: https://janoshik.com/verification/
• Freedom Diagnostics Testing, COA lookup: https://freedomdiagnosticstesting.com/search-for-your-coa-based-on-the-unique-accession-number/

Research Use Only Disclaimer: All QC Labs products are sold strictly for laboratory research use only (RUO). They are not intended for human or veterinary use, are not drugs, foods, dietary supplements, or cosmetics, and are not intended to diagnose, treat, cure, mitigate, or prevent any disease. This article is for educational and informational purposes only and does not constitute medical advice. Nothing in this article should be read as a claim about safety or effectiveness in humans. See our full research-use disclaimer.

For research use only. Not for human or veterinary use.