How to Read a Certificate of Analysis for Research Peptides

A Certificate of Analysis (CoA) is the only objective document tying a vial in your freezer to the lab work that proved it contains what the label says. If you cannot read a CoA, you are trusting marketing copy. This guide walks through every standard section, what good data looks like, and the specific patterns that should make a researcher walk away.

What a CoA is — and what it is not

A CoA is a per-lot analytical report produced after a peptide is synthesized, cleaved, purified, lyophilized, and packaged. It documents the tests run on that specific lot and the numerical results. It is not a certification of identity by a regulatory body, and it is not transferable between lots — a CoA for Lot 24-A12 tells you nothing about Lot 24-B07 of the same compound.

Every lot you receive should have its own CoA, dated within a reasonable window of the release date stamped on the vial. If a vendor cannot produce a lot-specific CoA on request, treat the material as unverified. HelixCore publishes every lot in our open CoA library, indexed by product and lot number.

The header: identity and provenance

The top of a competent CoA carries five pieces of information:

• Product name and sequence. The full one-letter amino-acid sequence should be printed. For BPC-157 this is GEPPPGKPADDAGLV; for GHK-Cu it is GHK complexed with Cu²⁺. If the sequence is missing, the CoA is incomplete.
• Lot or batch number. Must match the printed label on the vial. Mismatches are a red flag — either the document was copy-pasted from an earlier lot, or the vial was repackaged.
• Date of manufacture or release. Peptide stability for lyophilized material is generally stated as 24+ months at −20°C, but the clock starts here.
• Synthesizing lab and analytical lab. Often the same facility, sometimes different. If the analytical work is contracted out, the third-party lab's name should appear.
• Analyst signature or initials. An unsigned CoA is a template, not a report.

Identity: mass spectrometry

Identity is established by mass — specifically, by measuring the monoisotopic mass of the synthesized peptide and comparing it to the theoretical mass calculated from its amino-acid sequence. The standard technique is electrospray ionization mass spectrometry (ESI-MS), sometimes paired with MALDI-TOF.

On the CoA you should see:

• A theoretical mass (calculated from the sequence).
• An observed mass (measured by the instrument).
• The two should agree to within roughly ±1 Da for peptides under ~3 kDa, or the ppm error should be in the single digits.

Purity: reverse-phase HPLC

Purity is measured by reverse-phase high-performance liquid chromatography (RP-HPLC), almost always with UV detection at 214 nm (the wavelength at which the peptide amide bond absorbs). The output is a chromatogram — a plot of detector signal against retention time — and the purity number on the CoA is the area percentage of the main peak relative to total integrated area.

What "99% pure" actually means:

• The main peak represents 99% of the total UV-absorbing material in the sample.
• It does not mean 99% peptide by mass — water, counter-ions, and salts are not UV-active at 214 nm and do not appear on the chromatogram.
• It does not certify identity. A 99% pure wrong peptide is still 99% pure. This is why MS and HPLC are read together.

What to look at on the chromatogram itself:

• Peak shape. The main peak should be sharp and symmetric (Gaussian). Fronting or tailing suggests column overload or chemical instability.
• Baseline. Should be flat before and after the main peak. A drifting or noisy baseline can hide small impurities.
• Side peaks. Small peaks near the main peak are usually diastereomers or deletion sequences (peptides missing one amino acid). Peaks far from the main peak may be solvent, scavengers, or unrelated contaminants.
• Gradient and column information. A real chromatogram labels the column, the mobile-phase gradient (typically water/acetonitrile with 0.1% trifluoroacetic acid), and the flow rate. Missing methodology means you cannot independently evaluate the separation.

Water, residual solvents, and counter-ions

These tests are not always included on every CoA but should appear for any vendor making purity claims for sensitive applications:

• Water content (Karl Fischer titration). Lyophilized peptides typically come in at 4–8% residual moisture; values above ~10% suggest incomplete drying and may affect stability.
• Residual TFA. Trifluoroacetic acid is used in HPLC purification and synthesis cleavage. Many peptides ship as TFA salts; if the application requires an acetate salt, this needs to be specified.
• Net peptide content. The actual percentage of peptide by mass in the powder, accounting for water and counter-ions. A vial labeled "5 mg" may contain 4.3 mg of net peptide; this is normal.

Red flags

Putting it together

A complete CoA review takes about three minutes once you know what you are looking at. The flow is:

1. Match the lot number on the CoA to the vial label.
2. Check the sequence against an independent source.
3. Look at the observed mass vs. theoretical mass.
4. Inspect the HPLC chromatogram for peak shape and baseline.
5. Read the purity area percentage.
6. Confirm date, analyst, and analytical lab.

Every lot HelixCore ships passes this review before release, and the source documents are public — pick any product in our catalog and the CoA library will show you the actual reports we generate internally, not summary cards.