How to Read a Peptide Test Result (COA Guide)

A peptide test result, usually presented as a Certificate of Analysis (COA), tells you two things: what the substance actually is (identity) and how pure it is (purity). Identity is normally confirmed by mass spectrometry, and purity is measured by HPLC. Learning to read these fields is the only reliable way to check a product against its label. This article is educational and not medical advice.

What is a Certificate of Analysis (COA)?

A COA is a laboratory document reporting the test results for a specific sample. A meaningful COA names the sample, the methods used, the date, and the laboratory, and reports measured values rather than vague reassurances.

A genuine COA generally includes:

• The sample name and batch or lot number
• The test methods used (e.g. HPLC, mass spectrometry)
• The measured purity percentage
• The identity confirmation result
• The testing date and the laboratory’s name

If a “COA” is just a logo and a percentage with no method, no batch number and no lab identity, it is closer to marketing than to data.

What is the difference between purity and identity?

These are the two most important and most confused concepts. Identity answers “what is this?” and purity answers “how much of it is the real thing?” A product can pass one and fail the other.

Term	Question it answers	How it’s measured	What a fail looks like
Identity	What is this substance?	Mass spectrometry (MS)	The molecular mass doesn’t match the claimed peptide
Purity	What % is the claimed substance?	HPLC	Large or numerous impurity peaks; low %

Why this matters: a vial could be 99% pure, but 99% pure of the wrong molecule. Or it could be correctly identified as BPC-157 but only 70% pure, with the rest being unknown impurities. You need both answers.

How do you read HPLC purity?

HPLC (high-performance liquid chromatography) separates the components of a sample and measures how much of each is present. On a chromatogram, the target peptide shows as a large peak, and impurities show as smaller peaks.

What the purity number means

The reported purity percentage is essentially the area of the main peak as a proportion of the total. So “98.5% purity” means the main peptide accounts for 98.5% of the detected material, with 1.5% being impurities.

• Research peptides are commonly reported at 95%+, with many quality references aiming for 98%+.
• A higher percentage means fewer impurities - if the COA is genuine and tied to the actual product.

How to read the chromatogram

• One dominant, sharp peak = a clean result.
• Several sizeable peaks = significant impurities.
• A broad or split main peak can indicate degradation or a mixture.

How does mass spectrometry confirm identity?

Mass spectrometry measures the molecular mass of the compound. Each peptide has a known, expected mass based on its amino acid sequence, so MS confirms identity by checking whether the measured mass matches the expected mass.

In practice, the COA will state the expected (theoretical) mass and the observed mass. If they match within the method’s tolerance, identity is confirmed. If the observed mass is different, the product is not the peptide it claims to be, regardless of how pure it is.

Worked example: reading a sample COA

Suppose a vial is labelled “BPC-157, 5mg”. A COA comes back with the following:

Field	Reported value	Interpretation
Sample	BPC-157	The claimed identity
Method (identity)	LC-MS	Mass spectrometry used to confirm identity
Expected mass	1419.5 Da	The theoretical mass for BPC-157
Observed mass	1419.6 Da	Matches, identity confirmed
Method (purity)	HPLC	Purity measured by chromatography
Purity	98.7%	Main peak is 98.7% of detected material
Batch / lot	BPC-2406-A	Ties the result to a specific batch
Lab	(named laboratory)	Allows the result to be verified

In this example, identity is confirmed (the observed mass matches) and purity is high (98.7%). That is a strong result. Now compare it to a red-flag scenario: a “COA” that shows “99% purity” but no mass spec, no batch number, and no laboratory name. That document tells you nothing reliable about identity, and may not even relate to the vial in your hand.

What are the common red flags?

The biggest red flags are missing information and results that can’t be tied to the actual product. A high purity number is meaningless if the certificate is generic, undated, or unconnected to the batch.

Watch for:

• No batch/lot number - the COA can’t be matched to your specific product.
• No method listed - “99% pure” with no explanation of how it was measured.
• Purity only, no identity - you don’t know it’s even the right molecule.
• No laboratory named - the result can’t be independently verified.
• A COA reused across many products - a single generic certificate copy-pasted onto everything.
• Images of a chromatogram with no axis labels or scale.

Why is grey-market product often mislabelled or underdosed?

Because unregulated products are made without enforced manufacturing standards, the contents frequently don’t match the label. Independent testing repeatedly finds peptides that are underdosed, the wrong compound, or contaminated.

This is true across the board, from research peptides like BPC-157 to compounded versions of approved medicines like semaglutide. As we explain in our semaglutide vs tirzepatide comparison, grey-market and compounded products carry real quality and safety risks precisely because nothing forces the contents to match the label.

This is why independent verification exists. If you want a product checked, our testing service reports purity by HPLC and confirms identity by mass spectrometry, giving you the two data points that actually matter, rather than relying on a label or a supplier’s own certificate.

The bottom line

Reading a peptide test result comes down to two questions: is it the right molecule (identity, confirmed by mass spectrometry) and how pure is it (purity, measured by HPLC). A trustworthy COA names the sample, the batch, the methods and the lab, and reports both values. Anything less is marketing, not data.

Understanding this matters because regulated and unregulated products are worlds apart. To understand which peptides are even legal to import and use in Australia, read Are peptides legal in Australia?, and for a worked example of an unapproved research peptide, see What is BPC-157? This article is general educational information and not medical or legal advice.