How to read a peptide COA — a step-by-step guide for beginners

If you've never read a Certificate of Analysis before, they can look like gibberish. This guide walks you through every section of a typical peptide COA so you know exactly what you're looking at.

What is a COA?
A Certificate of Analysis is a document from a testing laboratory that confirms the identity, purity, and quality of a specific batch of product. For research peptides, a proper COA is the closest thing you have to a guarantee that what's in the vial is what the label says.

Section 1: Product identification
Look for: product name, catalog/batch number, molecular formula, molecular weight, CAS number (unique chemical identifier), and the manufacturer or vendor name. The batch/lot number is critical — it should match what's on your vial. If the COA doesn't have a batch number or the batch doesn't match your product, it might be a generic COA used across all batches (which is less trustworthy).

Section 2: Appearance
Usually states something like "white to off-white lyophilized powder." This is a basic organoleptic test — the lab confirms the product looks like what it should look like. Minor, but a starting point.

Section 3: HPLC Purity
This is the most important number on the entire document. HPLC (High-Performance Liquid Chromatography) separates the sample into its components and measures what percentage is the target peptide vs impurities.

What to look for: Purity above 97% is generally acceptable for research peptides. Above 98% is good. Above 99% is excellent. Below 95% is concerning — the remaining 5%+ could be synthesis byproducts, degradation products, or other contaminants.

The HPLC chromatogram (the graph): You should see one dominant peak representing the target peptide. Small minor peaks are normal — these are trace impurities. If you see multiple large peaks of similar size, something is wrong. The main peak should be dramatically larger than everything else.

Section 4: Mass Spectrometry (MS)
Mass spec confirms the molecular identity of the peptide. The observed molecular weight should match the theoretical molecular weight for that peptide (within a narrow margin). This confirms that the peptide is actually what it claims to be, not just that something is pure.

Example: BPC-157 has a theoretical molecular weight of 1419.53 Da. The MS result should show an observed mass very close to this number. If the observed mass is significantly different, the product is not BPC-157 regardless of what the label says.

Section 5: Amino acid analysis (if included)
This confirms the amino acid composition matches the expected sequence. Not all COAs include this — it's an additional quality check that higher-end testing provides.

Section 6: Endotoxin testing (if included)
Bacterial endotoxins are lipopolysaccharides from gram-negative bacteria. They can cause fever, inflammation, and serious immune reactions if injected. The standard limit for injectable products is less than 5 EU/mg. This test is particularly important for injectables and is a sign of higher quality testing.

Section 7: Solubility and pH
Confirms the peptide dissolves properly and the solution pH is within expected range. Minor but relevant for reconstitution quality.

Red flags on a COA:
No batch/lot number. No lab name or accreditation number. Purity below 95%. Missing mass spectrometry data (HPLC alone doesn't confirm identity). The document looks like a template with no specific data. Multiple COAs from the same vendor showing identical numbers across different batches (statistically unlikely). Blurry, low-resolution images that prevent reading specific values.

What a strong COA looks like:
Named third-party lab with accreditation. Specific batch number matching your product. HPLC purity above 98% with chromatogram included. Mass spectrometry confirming molecular weight. Clear, high-resolution document with the lab's letterhead, date, and analyst signature.

Save every COA you receive. Compare COAs across vendors for the same peptide. Over time, you'll develop an eye for quality and spot questionable documents quickly.