How to Read a Peptide Certificate of Analysis (COA)

For laboratory and research-supply use only. The intent of this guide is to help researchers interpret quality documentation when sourcing peptides. Nothing here constitutes medical or clinical guidance.

A Certificate of Analysis (COA) is the single most important document a research peptide should ship with. It is the supplier’s statement, ideally backed by third-party laboratory data, of what is actually in the vial. A COA without supporting analytical data is a product label, not a quality document.

This article walks through the fields of a typical peptide COA and explains what each one means, what “good” looks like, and which red flags should make you pause before purchasing.

Anatomy of a peptide COA

A complete COA generally contains the following sections.

1. Product identity

• Product name — the trade or research name (e.g., “BPC-157”).
• Sequence — the explicit amino-acid sequence in one-letter or three-letter code. Critical: trade names like “TB-500” are not strict chemical identifiers; the sequence on the COA is.
• Molecular formula and molecular weight.
• CAS number, when one exists.

2. Lot or batch identification

• Lot/batch number — must match the number printed on the vial. If it doesn’t match, the COA is not for the product in your hand.
• Manufacture date — combined with shelf-life guidance below, this tells you how much of the stable life is left.
• Expiry / re-test date — the date by which the supplier has guaranteed the assayed properties hold.

3. Analytical results

This is the core of the COA. Look for:

• HPLC purity — expressed as a percentage. For most published preclinical work, ≥98% is the target. Anything below 95% is unusual for a commercial research peptide.
• Mass spectrometry result — the observed molecular weight. It should match the theoretical molecular weight stated in the identity section to within standard MS tolerances.
• Water content — usually by Karl Fischer titration. High water content in a lyophilized peptide is a stability red flag.
• Acetate / TFA content — counter-ion content from the synthesis process. Affects net peptide mass per vial.
• Appearance — usually “white to off-white lyophilized powder.” Anything else warrants a question.

4. Accompanying analytical data

A high-quality COA includes the actual chromatograms and spectra, not just the summary numbers:

• HPLC chromatogram showing a single dominant peak. Multiple comparable peaks suggest multiple species in the vial.
• Mass spec trace with the major ion peak labeled and matching the expected mass.

Research note: If a supplier provides only a summary table with no chromatograms or spectra, ask for the underlying data. Reputable third-party labs always produce them.

5. Storage and handling

• Recommended storage temperature (typically −20°C for lyophilized).
• Reconstitution recommendations — solvent and concentration ranges.
• Handling cautions — light, humidity, freeze-thaw.

For more on this section in practice, see our peptide storage guide.

6. Issuing party and signatures

• Issuing laboratory. A COA from an independent, ISO-accredited testing lab carries more weight than one issued purely by the manufacturer.
• Date of testing and analyst signature (or electronic signature). Both should be present.

Red flags

1. No COA at all, or a COA generated only as a generic template not tied to a specific lot.
2. Lot number on the COA does not match the vial. Common when a supplier reuses an old COA for a new batch.
3. No chromatograms or mass-spec traces, only summary numbers.
4. HPLC purity stated to several decimal places without a chromatogram—real instruments do not justify that precision.
5. Appearance description that doesn’t match what’s in the vial.
6. COA dated long before the manufacture date—the tested material is not the material shipped.

What to do with the COA after purchase

• File it with the lot number; treat it as a primary lab record.
• When you publish or share results from work using the peptide, cite the lot and supplier.
• For long-running studies, request fresh COA testing from the supplier before reordering — some suppliers re-assay aged stock and re-issue updated COAs.

Further reading

For background on the most-discussed research peptides, see our BPC-157 research guide and GHK-Cu research overview.

Reminder: All information above is for in-vitro and laboratory research purposes. PrimeHelix Labz products are not intended for human consumption.