How to Read a Peptide Certificate of Analysis

Start with the lot number

A certificate describes one batch. Before reading any figure, confirm the lot number on the certificate matches the lot number on the label. A certificate for a different batch tells you what a different batch measured. On nearly all the lots we publish, the code ends in the month and year of manufacture, so lot BPC10VBG0326 was made in March 2026. That gives a quick cross-check: if a code’s suffix and the stated manufacture date disagree, ask the supplier which one is right.

• Look up published results by lot number
• Glossary: lot number

A worked example: BPC-157 lot BPC10VBG0326

Here is how the published results for one real lot read, line by line. Lot and dates: BPC10VBG0326, received by AxisPharm, LLC on 2026-03-25 and reported 2026-03-25, manufactured 2026-03, best before 2028-03. The report date is on or after the received date, as it must be. Purity: >99.5% by HPLC-UV (208 nm). The ">" means the laboratory is reporting a threshold the main peak cleared, not an exact figure. Identity: 1421.1 [M+H] by LC-MS (ESI+). The molecular weight is 1419.5 g/mol; adding one proton gives an expected [M+H] of about 1420.5, and the measured 1421.1 sits within the tolerance of routine LC-MS. Identity is confirmed. Quantity: label claim 10 mg, measured 10.1 mg. The tested material meets its label claim. Endotoxin: 0.057 EU/mg by LAL assay.

• Lot BPC10VBG0326 — full published results
• BPC-157 — all published lots

Purity: what the HPLC figure tells you

Purity by HPLC is the share of the detected peptide signal that belongs to the target sequence rather than truncated or modified versions of it. It is calculated as an area percentage of the chromatogram peaks. Detection wavelength matters: low-UV detection around 205 to 220 nm sees the peptide bond itself, so it works for any sequence, while 280 nm relies on aromatic residues and can misreport sequences that lack them. Purity describes the peptide material only. It does not tell you how much material is in the vial; that is the quantity line. The chromatogram behind the figure is part of the laboratory’s certificate, and you can request the certificate for any lot you hold.

• Glossary: 208 nm detection
• Glossary: area percent
• Glossary: chromatogram

Identity: reading the mass spectrometry line

LC-MS answers a different question from HPLC: is this the right molecule? The instrument measures ions, not neutral molecules, so the reported mass carries a label. [M+H] means the molecule plus one proton, so it reads about 1 Da above the molecular weight. Larger peptides often pick up two or three protons and appear as [M+2H] or [M+3H] at roughly a half or a third of their mass: a peptide of about 4,730 Da shows up near 2,367 and 1,578. Other labels such as [M+Na] are adducts, where a sodium or similar ion attached instead of a proton. One rule follows directly: a detected [M+H] can never be lower than the molecular weight. If it is, the ion is mislabelled or a figure is mistyped.

• HPLC purity vs. mass spectrometry identity
• Glossary: adduct

Quantity: label claim, measured content and peptide content

The certificates behind our lots report measured content against the label claim: the laboratory weighs what is actually present and states it next to what the label says. A 10 mg claim measured at 10.1 mg means the vial holds what it states. Some laboratories instead report peptide content, a percentage of net weight that is peptide as opposed to counterion, water and salts. The two are different measurements and should not be compared directly. For concentration work, start from the measured figure; if a certificate gives peptide content, apply it as well. Some laboratories also report water content or solvent traces; the certificates behind our lots do not include those assays.

• Peptide stock solution calculator
• Glossary: label claim
• Glossary: peptide content

Endotoxin, and what a blank means

Endotoxin is measured by the LAL assay and reported in endotoxin units per milligram (EU/mg). It matters most for cell-based work, where bacterial endotoxin can affect results independently of the peptide. Not every lot is tested for it. On our lot pages an endotoxin figure appears only when the laboratory measured it; where it was not tested, no figure is shown. A blank means not measured. It does not mean zero.

• Glossary: endotoxin
• Glossary: LAL assay

Errors we have found on real certificates

Every certificate we receive is read line by line before its results go on the site, and genuine laboratory certificates do contain mistakes. The kinds we have caught: a lot number with two digits transposed; the same certificate ID printed on reports for two different products; a label-claim field that contradicts the sample name on the same page; a detected [M+H] lower than the stated molecular weight; a results table describing a molecule roughly ten times the size of the one named; a purity header giving one detection wavelength while the chromatogram shows another; a test date earlier than the date the sample was received; and a copper peptide reported at the mass of its copper-free form. None of these is visible from a purity figure alone, which is why the whole certificate is worth reading. Where an error could mislead, we hold the results back until the laboratory issues a corrected certificate.

Red flags on any certificate

Identical purity figures across several different compounds suggest numbers are being written rather than measured, since real results vary. A certificate with no named laboratory cannot be verified. One with no date, or dates in an impossible order, cannot be matched to a batch. A lot number that does not appear on the product, or the same certificate supplied for material bought months apart, is decorative rather than evidential. Low-resolution images where the figures cannot be read should be treated as absent.

Independent testing means the lab has no stake in the result

In-house quality control is a normal part of manufacturing, but it is not independent verification. What matters is whether the laboratory performing the analysis has a commercial interest in the outcome. A certificate should name the testing laboratory. If the manufacturer and the tester are the same entity, the certificate is a self-report, which may still be accurate but is a different category of evidence and should be described that way.

• Glossary: third-party testing