A certificate of analysis (COA) is the single most important document in research peptide sourcing. It is the difference between a labeled claim — “≥99% purity” — and a measurable, lot-specific fact. This guide walks through each section of a professional COA, what the numbers actually mean, and the red flags that should end a purchase before it starts.
What a COA is (and what it is not)
A COA is a lot-specific analytical report, produced when a batch of material is tested against defined specifications. A real COA is tied to a lot number printed on the vial in your hand. A generic PDF with no lot number, no test date, or no analytical method listed is a brochure, not a certificate.
At Heartland Bio Labs, every product ships with its lot number on the label, and every lot’s certificate is published in our public COA portal — enter the lot number and read the actual document before or after purchase.
Section 1: Identity — mass spectrometry
Purity means nothing if the compound is wrong. Identity testing confirms the molecule is what the label says, usually by ESI-MS or MALDI-TOF mass spectrometry. The COA should state the theoretical molecular weight of the peptide and the observed mass from the instrument. Those two numbers should agree within a fraction of a dalton per charge state.
Example: BPC-157 has a theoretical monoisotopic mass near 1419.5 Da. An observed mass far from the theoretical value — or a COA with no observed mass at all — means the identity was never actually confirmed.
Section 2: Purity — HPLC
High-performance liquid chromatography (HPLC) separates the target peptide from synthesis by-products and degradation products. Purity is reported as the target peak’s share of total peak area, typically at 214 nm or 220 nm where peptide bonds absorb.
- ≥99% — high-grade research material; the standard every Heartland lot must meet.
- 95–98% — common for complex or very long sequences; acceptable for many research applications when disclosed honestly.
- No chromatogram shown — a purity number without the supporting trace deserves skepticism.
Section 3: Appearance and physical description
Lyophilized peptides should be described (white powder, off-white cake, etc.) and the vial you receive should match. A COA that describes a white lyophilized cake for a vial that arrives as glassy film or discolored residue is describing a different lot — or a different product.
Section 4: The details that prove it is real
- Lot/batch number that matches your vial exactly
- Test date reasonably close to the product’s release
- Method listed per result (HPLC conditions, MS instrument type)
- Quantity/fill verification where stated (a 10mg label should be backed by fill data)
Red flags in the wild
- The same COA image reused across multiple products or strengths.
- Purity claimed to more decimal places than the method supports.
- No public way to look up a lot — certificates only “available on request.”
- A “COA” that is actually a supplier invoice or a stock photo of paperwork.
Verify before you rely
Documentation you can verify beats claims you have to trust. Browse the research catalog, note any lot number, and pull its certificate in the COA portal — that workflow is the standard we believe every research supplier should meet.
All products discussed are for in vitro laboratory research use only and are not for human or veterinary use.