How to read a Certificate of Analysis
A Certificate of Analysis (COA) is a signed technical document issued by an independent laboratory that certifies the identity, purity, and contaminant profile of a specific production lot. If a supplier cannot produce a current, batch-specific COA, nothing else they say about their product can be verified.
Every good COA has three blocks. The header identifies what was tested: product name, CAS/identifier if applicable, batch or lot number, manufacture date, retest or expiry date, quantity released, and the issuing laboratory. The test results block contains each analytical assay, the method used, the specification (pass criterion), and the observed result. The release block contains the analyst's or quality officer's signature, the issuing lab's accreditation, and the date of release.
Identity confirmation. The analytical chemistry question here is simple: is the molecule in the vial actually what the label says it is? For peptides, the modern standard is a high-resolution mass spectrometer (HRMS) paired with HPLC — HPLC-MS. The observed mass is compared to the theoretical monoisotopic mass calculated from the amino acid sequence. A match within 0.01 Da (10 ppm) is the expectation; a mismatch is a hard fail. Many COAs also include amino acid analysis (AAA) as a secondary confirmation: the peptide is hydrolyzed and the amino acid ratios are measured against the expected composition.
Purity by HPLC. This is the number most readers look at — but the percentage alone is only half the picture. The assay is reverse-phase HPLC with UV detection, typically at 214 nm (peptide bond absorbance) or 280 nm (aromatic residues). The purity figure is the integrated area of the main peak divided by the total integrated peak area, expressed as a percentage. 98% is a reasonable floor for research-grade material; 99%+ is the specification serious EU and US GMP facilities release against. When you see a chromatogram on a COA, look for a sharp, symmetrical main peak with a flat, low baseline. A clean 99.2% is better than a noisy 99.8% — the latter often means impurities are co-eluting with the main peak and being undercounted.
Residual solvents. Peptide synthesis uses organic solvents: TFA (cleavage), DMF or NMP (coupling), acetonitrile (HPLC purification), methanol and DCM (workup). Good COAs quantify these per the ICH Q3C guideline, which groups solvents into three classes with specific limits in parts-per-million. Class 1 (benzene, carbon tetrachloride, 1,1-dichloroethane) should be avoided entirely. Class 2 (acetonitrile, DCM, methanol, DMF) is limited — for example, acetonitrile must be below 410 ppm. Class 3 (acetone, ethanol, ethyl acetate) has looser limits (50 mg/day). If your use case is injectable research work, these numbers matter directly.
Endotoxin. Gram-negative bacteria shed lipopolysaccharides that trigger inflammatory responses at microgram-scale doses. Endotoxin is measured by the LAL (limulus amebocyte lysate) assay, most sensitively in its kinetic chromogenic form. Results are reported in endotoxin units per milligram (EU/mg). For injectable research applications, the USP rule of thumb is < 5 EU/kg/hour total exposure — back-calculate from your expected dose to your acceptance threshold. A COA that omits endotoxin data should raise questions if the compound is intended for injection.
Red flags. (1) No batch or lot number — you cannot link the document to the vial. (2) No issuing lab name or signature. (3) Suspiciously round purities (99.0%, 100.0%) — real HPLC numbers have decimal places and the method precision is ± 0.2% at best. (4) A single COA reused across multiple production dates. (5) No retest or expiry date. (6) Identity by "visual inspection" or "supplier certificate" rather than an actual analytical method. (7) Unit mismatches — μg/mg confusion in endotoxin reporting is a common laundering trick.
What a Vivaprime COA looks like. Every batch released from our EU facility carries a document with the header block described above, plus: HPLC-UV purity chromatogram with the main peak integrated, HPLC-MS identity confirmation with theoretical vs observed mass, residual solvent quantitation per ICH Q3C for each solvent used in synthesis, and endotoxin by kinetic chromogenic LAL. The release is signed by the facility's QA officer with the accreditation body reference. Every batch is linked from its specific product page on this site.
A practical receiving workflow. When a pen arrives: (1) note the batch number printed on the pen. (2) Open the matching product page on this site and the linked COA. (3) Confirm the batch numbers match. (4) Confirm the test date on the COA is within the retest window. (5) Confirm the purity figure on the product page matches the COA. (6) Archive the COA PDF locally — laboratory records should not depend on third-party URLs remaining accessible. If any of these checks fail, do not use the material and contact the supplier.
A COA is the closest thing a research supplier has to a receipt of integrity. Read it like one.