Interpreting a peptide COA

A certificate of analysis is a technical document, not a marketing asset. This guide walks through each section of a standard Janoshik peptide COA — what every number means, how to cross-check identity against theoretical mass, what the HPLC chromatogram is actually showing, and the specific red flags that separate a credible analytical report from a decorative one.

Document header

The first section of a Janoshik COA is metadata: the lab name and address, a unique document reference number that the lab maintains in its internal database, a date of analysis, the sample name as submitted by the client, and a batch or lot identifier. The reference number is the single most important field for cross-verification — any researcher can contact the lab with that reference number and confirm that the document they are holding was, in fact, issued by the lab for the stated sample. A "COA" without a reference number is not a COA; it is a document that happens to be shaped like one.

The sample name field should match the peptide name printed on the vial label exactly. A discrepancy — a report for "BPC-157 5mg" that is being presented as coverage for a "BPC-157 10mg" vial — is not a match. A batch identifier should be present and should tie the document to a specific lot of synthesized material, not merely a product name, so that two different batches of the same peptide get two different COAs.

HPLC section

The HPLC section is usually the largest block on the page. It contains a chromatogram image and a summary table. The chromatogram is a plot of UV absorbance versus retention time. A well-synthesized peptide appears as a single dominant peak with a roughly symmetric gaussian shape, small baseline noise, and no other significant peaks anywhere in the run. The retention time tells you nothing about purity by itself but is a useful fingerprint — the same peptide run on the same column and gradient should elute at a reproducible time.

The summary table lists each peak, its retention time, its integrated area, and its percentage of total area. The purity number on the top of the page is the main-peak percentage from this table. Reading the table rather than only the headline number is valuable: it reveals what the remaining percentage is made of. A 99.0% pure sample with a single 1.0% impurity at a retention time close to the main peak is a different situation than a 99.0% pure sample with ten separate 0.1% impurities scattered across the run. The former usually indicates a specific deletion or truncation byproduct; the latter usually indicates a generally noisy synthesis.

Instrument method parameters should also be listed: column identity and dimensions, mobile-phase composition (typically water/acetonitrile with 0.1% TFA or formic acid), gradient profile, flow rate, and detection wavelength. 214 nm is the peptide-bond absorbance wavelength and is the standard; reports that use only 280 nm (which measures Trp/Tyr absorbance and is sequence-dependent) understate impurities that do not contain those residues. The general framework for HPLC purity analysis of synthetic peptides is discussed in D'Hondt et al. (J Pharm Biomed Anal 2014, PMID: 24858305).

Mass-spec section

The mass-spec section reports the observed molecular mass of the main HPLC peak, typically from ESI-MS, and should include the raw m/z spectrum as an image. For identity confirmation, the researcher compares the reported observed mass against the theoretical mass calculated from the declared amino-acid sequence. Theoretical masses are computed by tools such as ExPASy Compute pI/Mw (Gasteiger et al., The Proteomics Protocols Handbook 2005, PMID: 15980573) or built-in calculators in peptide-synthesis software, using standard residue monoisotopic or average masses.

For BPC-157 with sequence GEPPPGKPADDAGLV, the theoretical average molecular mass is approximately 1419.55 g/mol for the free acid. A COA that reports an observed mass within about ±1 Da of the theoretical mass on a standard-resolution instrument — or within a few parts per million on a high-resolution instrument — confirms identity. A mass offset of exactly +16 indicates a single oxidation event (typical for peptides with methionine); +14 indicates methylation; +28 indicates formylation. These signatures are diagnostic and are the reason MS is the load-bearing identity check.

Peptide content by weight

The third assay on a complete peptide COA is peptide content by weight. This number is distinct from HPLC purity and is commonly missing or misrepresented on low-rigor reports. Peptide content quantifies how much of the total lyophilized vial mass is peptide, versus how much is trifluoroacetate or acetate counter-ion, bound water, and trace solvent residues. A research-peptide vial will typically report peptide content somewhere between 70% and 90% of total lyophilized mass, depending on the counter-ion form (TFA salts are heavier and lower the content number; acetate salts are lighter).

A vial labeled 5 mg with 80% peptide content contains 4 mg of net peptide and 1 mg of non-peptide mass. This is the number that drives accurate reconstitution math in any research protocol where mass precision matters. The methods used to quantify peptide content include amino-acid analysis after acid hydrolysis (AAA), quantitative NMR, elemental nitrogen analysis (Kjeldahl or Dumas), or UV absorbance with appropriate extinction coefficients. The method should be named on the report.

Red flags

Specific patterns mark a COA as unreliable. A PDF that is text-only, containing no chromatogram image or mass spectrum image, is not an analytical report — it is a typed claim. A report that lists an HPLC purity but does not disclose the detection wavelength, column, or gradient gives no way to evaluate whether the method is appropriate for the peptide. A report with a non-matching sample name, a missing reference number, a mismatched date, or a peptide name misspelled in the header suggests either a template-produced document or a genuine document that has been misassigned to a different product. An observed mass that does not match the theoretical mass for the declared sequence is either an identity failure or a typographical error that calls the rest of the document into question.

The defensive posture for a research buyer is to treat any one of these as a reason to request clarification from the vendor and, if clarification is not forthcoming, to treat the COA as non-authoritative. The cost of treating a suspect COA as real is that downstream in-vitro data is generated against a potentially incorrect molecule.

How Aurex presents COAs

Every Aurex batch has its Janoshik reference number printed on the vial label and encoded in a QR code. Scanning the code or entering the batch ID in the batch lookup tool pulls the specific Janoshik PDF that corresponds to the vial in hand. The PDF is the original document from the lab, not a reformatted summary, so the chromatogram, mass spectrum, and reference number are all intact and cross-verifiable with Janoshik directly if the researcher chooses to do so.

Frequently asked questions