How to Read a Peptide Certificate of Analysis

A Certificate of Analysis is the single most important document a peptide vendor can provide. It tells you what is in the vial, how pure it is and whether the product matches what the label claims. We reviewed COA documentation from every vendor in our catalog and found significant differences in what gets disclosed. This guide explains each section of a peptide COA, what the numbers mean and what their absence should tell you.

What a Certificate of Analysis Is

A Batch-Specific Lab Report

A COA is a document issued by an analytical testing laboratory for a specific batch or lot. For peptides, it reports the results of tests performed on that particular production run. A properly issued COA includes the lot number, date of analysis, identity of the testing laboratory and results of each test. It applies to one batch only. If your vial's lot number does not match the COA, the document does not apply to your product.

Why It Matters for Research Peptides

Research peptides are sold without FDA oversight of manufacturing quality. The COA is the buyer's only independent verification that the product contains what the vendor claims. Without it, you are relying entirely on the vendor's word. We treat COA availability as a baseline requirement when evaluating products for our brand catalog.

Key Sections of a Peptide COA

HPLC Purity Percentage

High-performance liquid chromatography separates the target peptide from impurities. The result is a percentage by area normalization. A reading of 98.5% means that 98.5% of the total peak area corresponds to the target peptide. The remainder consists of truncated sequences, deletion peptides and oxidized forms. For research-grade peptides, 98% or higher is the standard. Values below 95% indicate significant non-target material. See our HPLC purity testing guide for more detail.

Mass Spectrometry (MS) Identity Confirmation

Mass spectrometry measures the molecular weight of the peptide. For BPC-157, the expected weight is 1419.5 g/mol. A match within instrument tolerance (plus or minus 1 dalton) confirms identity. MS does not measure purity. It confirms that the main component is the correct peptide. A COA with HPLC but no MS tells you the sample is pure without confirming what it is pure of.

Endotoxin and Sterility Testing

Endotoxins are bacterial cell wall fragments measured by the LAL test in endotoxin units per milligram. Research-grade peptides should test below 1 EU/mg. Sterility testing confirms absence of viable microorganisms. Not all vendors perform these tests.

Residual Solvent Analysis

Peptide synthesis uses organic solvents including DMF, acetonitrile and TFA. Residual solvent analysis confirms these have been removed to ICH Q3C guideline levels. Most research peptide COAs do not include this test, which is more common in pharmaceutical-grade manufacturing.

Reading an HPLC Chromatogram

The Main Peak and Impurity Peaks

A chromatogram plots retention time (x-axis) against signal intensity (y-axis). The target peptide appears as the tallest peak. Impurity peaks are smaller peaks at different retention times. A single dominant peak with a clean baseline indicates a well-purified product. Multiple peaks of comparable height suggest a mixture.

Area Normalization Method

Purity equals the target peak area divided by total area of all peaks. This method assumes similar UV absorbance rates across peptide components, which is approximately true for related synthesis byproducts.

Red Flags on a COA

No Lot Number

A COA without a lot number cannot be tied to a specific batch. It may be a template reused for every shipment. Lot-specific COAs are generated per batch.

No MS Data

HPLC purity without mass spectrometry means you know the sample is chemically pure but not whether it is the correct peptide. Different peptides of similar size can produce comparable HPLC profiles.

Purity Below 95%

Research-grade peptides should exceed 95%. Values below this indicate suboptimal synthesis or inadequate purification.

Generic or Undated Document

A COA lacking a date, using a generic template or not naming the testing laboratory may not represent actual testing. Compare the lot number on your vial to the COA. If they do not match, the document is irrelevant to your product.

Vendors in Our Catalog: COA Status

We update this table when vendors change their COA policies. Real Peptides is the only vendor publishing lot-specific COAs with both HPLC and MS data on the product page. The absence of a published COA does not prove impurity. It means the buyer cannot independently verify it.

What a Missing COA Tells You

Without a COA, you lose verification of three things: that the product is the correct peptide, that it meets a minimum purity standard, and that your specific batch was tested. Some vendors provide COAs upon request. A vendor that refuses any documentation is a vendor we cannot recommend. For an explanation of the HPLC process referenced here, see our HPLC purity testing guide.