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COA Decoder

Paste the text of a peptide certificate of analysis. The decoder reads the identity, purity, lot, date and test results it contains and explains, in plain language, what they show, what they cannot show and which red flags to look for. It interprets documents; it never rates or recommends a seller. Nothing you paste leaves your browser.

What a certificate can and cannot show

HPLC purity is the share of the ultraviolet signal that falls in the main peak of a chromatogram. It says how clean the sample looks to that method, not what the main peak is. Impurities that elute with the main peak, or that absorb little ultraviolet light, can hide inside it, and the figure is a share of peak area, not of weight: water, salts and counter-ions in the powder are not counted. That is why the chromatogram matters more than the number printed beside it.

Purity figures in context. For the synthetic peptide generics it regulates, FDA expects each peptide-related impurity at 0.10% or more to be identified, and no new impurity above 0.5%.1,2 A research peptide sold at 98% can carry two percentage points of unidentified material, twenty times that identification threshold. No real measurement comes out at exactly 100%.

Mass spectrometry checks identity: the measured mass should match the peptide's expected mass, directly or as a protonated ion such as [M+H]+ or [M+2H]2+. A match shows the main component has the right mass. It cannot distinguish peptides of identical mass, such as a sequence with two residues swapped or an L-amino acid replaced by its D-form, and it says nothing about how much of the sample is that component.

Endotoxin testing looks for fragments of bacterial cell walls, which cause fever and inflammation when injected. Purity and mass tests do not detect them. The standard method is the Limulus amebocyte lysate (LAL) test, reported in endotoxin units (EU) per mg.3

Laboratory accreditation. ISO/IEC 17025 sets the requirements for a testing laboratory's competence, and accreditation bodies such as A2LA assess labs against it.4 Accreditation applies to specific methods, so a credible report names the method, and the lab's published scope of accreditation should include it.

What no certificate can show is that it belongs to your vial. Match the lot number to the label, look for a date after the batch was made, and when a report matters, ask the issuing laboratory whether it recognises the report number.

Sources

  1. US FDA. ANDAs for Certain Highly Purified Synthetic Peptide Drug Products That Refer to Listed Drugs of rDNA Origin: Guidance for Industry. May 2021. www.fda.gov
  2. US FDA, Office of Generic Drugs. Synthetic peptide ANDAs: impurity level qualification (SBIA 2022 presentation). www.fda.gov
  3. US FDA. Guidance for Industry: Pyrogen and Endotoxins Testing: Questions and Answers. June 2012. www.fda.gov
  4. ISO/IEC 17025:2017. General requirements for the competence of testing and calibration laboratories. www.iso.org

Rules and wording: coa-rules.json, updated 2026-09-27. Expected masses come from our encyclopedia when a certificate does not state one.