If you’re buying peptides from any vendor, the Certificate of Analysis (COA) is the single most important document you should review before putting anything in your body. A COA is third-party lab verification that the peptide is what it claims to be, at the purity it claims, free of dangerous contaminants. Here’s how to read one.
A Certificate of Analysis is a document issued by an independent analytical laboratory that tests a peptide product and reports its findings. It typically includes the peptide identity (is it actually the peptide on the label?), purity (what percentage of the product is the target peptide vs. impurities?), and safety testing (endotoxin levels, sterility, heavy metals). A legitimate COA comes from a third-party lab — not the vendor themselves. If a vendor provides a COA from their own internal lab, it’s worth less than the paper it’s printed on.
HPLC separates the components of a sample and measures what percentage is the target peptide. A research-grade peptide should be ≥98% pure. Anything below 95% is concerning. The HPLC chromatogram (the graph) should show one dominant peak (your peptide) with minimal smaller peaks (impurities). If the graph looks like a mountain range instead of a single spike, the product contains significant impurities.
Mass spectrometry confirms molecular identity by measuring the peptide’s molecular weight. Every peptide has a specific molecular weight. If the measured weight doesn’t match the expected weight within a tight tolerance, the product isn’t what it claims to be. This is your insurance against mislabeling or substitution.
Endotoxins are bacterial cell wall fragments that can cause fever, inflammation, and in severe cases, septic shock when injected. The LAL (Limulus Amebocyte Lysate) test measures endotoxin levels. Injectable peptides should have endotoxin levels below 5 EU/kg body weight per dose. If a vendor doesn’t test for endotoxins on injectable products, don’t buy from them.
| Red Flag | What It Means |
|---|---|
| No COA available | The vendor either didn’t test the product or is hiding results. Walk away. |
| COA from vendor’s own lab | Not independent verification. Meaningless. |
| Purity below 95% | Significant impurities. Don’t inject this. |
| No mass spec confirmation | You can’t verify the peptide is what it claims without MS. |
| No endotoxin test (for injectables) | Potentially dangerous bacterial contamination. |
| Batch number doesn’t match your product | The COA may not correspond to what you received. |
| Old COA date | Testing should be recent and batch-specific. A COA from 2 years ago doesn’t tell you about today’s product. |
The vendors we recommend on this site (BioPure, Apollo, Midwest, Amino Club) provide batch-specific, third-party COAs for every product. You should be able to access the COA before purchasing, verify the batch number matches your order, and see HPLC purity, mass spec confirmation, and endotoxin testing for all injectable products.
For injectable peptides, aim for ≥98% HPLC purity. 95-98% is acceptable for some research applications. Below 95% means significant impurities — don't inject it. For topical peptides (like GHK-Cu serums), slightly lower purity is more acceptable since they're not entering the bloodstream directly.
Reputable vendors provide batch-specific, third-party COAs for every product. If a vendor doesn't offer COAs, can't provide them upon request, or only shows a generic COA not tied to specific batches, find a different vendor. This is non-negotiable for injectable products.
HPLC tells you how pure the sample is (what percentage is the target peptide vs. impurities). Mass spectrometry tells you what the sample actually is (confirms molecular identity by measuring molecular weight). You need both: HPLC alone tells you the product is 99% pure, but not whether that 99% is the peptide you ordered. Mass spec confirms identity.
Yes. Peptides degrade over time, especially if improperly stored (exposed to heat, light, or moisture). A COA reflects the product's state at the time of testing. Proper storage (refrigerated, sealed, away from light) preserves the peptide's integrity. Reconstituted peptides degrade faster — use within 3-4 weeks when stored at 2-8°C.