How to read a peptide COA: HPLC and mass

Research-use notice: This article is laboratory and educational information only. It is not medical or legal advice, and it does not include how-to-use instructions. BlueNex Labs materials are research use only and are not intended for human or veterinary use. Research-use-only labelling is not a Health Canada authorization.

Publication status: Prepared for the BlueNex Labs Research Knowledge Centre. Literature and library notes checked September 24, 2026. Primary papers and the public COA library can change; verify the lot report in hand before an assay.

A peptide Certificate of Analysis is easier to misread than it is to open. The page usually shows a purity percentage in large type. That number is one line of a longer record: the method, the peak table, the mass, and any endotoxin result the laboratory actually ran. This note is the line-by-line reading. What a peptide COA records is the shorter primer on what the document is for. Live PDFs stay in the certificates library.

HPLC purity on the chromatogram

High-performance liquid chromatography, and the related higher-pressure methods often labelled UPLC, separates a mixture as it moves through a column. For peptides the usual arrangement is reversed phase: a hydrophobic column, a water-to-organic gradient, and an ultraviolet detector. Peptide bonds absorb near 214 nanometres, so many reports integrate at 214 or 220 nanometres. Aromatic residues also absorb near 280 nanometres. The wavelength is part of the method. A percentage from one wavelength is not automatically the percentage at another.

Purity, when the report means chromatographic area percent, is the area of the assigned peak divided by the sum of the peak areas the software integrated, multiplied by 100. Read the peak table, not only the headline. Note the retention time of the main peak, the number of secondary peaks, and whether the laboratory set a minimum area before a peak counts. A threshold hides small peaks. Say so in the receiving log if the report states the threshold, and do not guess one if it does not.

The chromatogram does not name the molecule. Two sequences with similar hydrophobicity can share a retention time. An impurity that co-elutes with the main peak inflates the area percent. A truncated sequence, a deletion, or an oxidized residue can appear as a later or earlier peak, or it can hide. That is why a purity figure is incomplete without the mass on the same lot. The arithmetic is expanded in HPLC versus LC-MS.

Mass spectrometry identity

Mass spectrometry reports a mass, usually from electrospray ionization as a mass-to-charge ratio that the laboratory deconvolutes to a molecular mass. Compare that observed mass with the mass calculated from the amino-acid sequence named on the label, including any terminal modification the method expects. A match supports identity for that sample. A mismatch means the sample is not the sequence you intended to file, even if the area percent is high.

Read which species the laboratory weighed. Synthetic peptides are often isolated as salts. Trifluoroacetate and acetate are common counter-ions. Sodium and potassium adducts shift a spectrum. If the report says "free peptide," "acetate," or "TFA salt," copy that phrase. If it does not, leave the salt form blank in the study file. Net peptide content cannot be worked out from gross weight unless the report prints it. Chromatographic purity and net content answer different questions. A clean chromatogram can still be a salt-heavy solid.

When the instrument is an LC-MS system, the chromatogram and the mass can come from one injection. They are still two results. The ultraviolet trace is the usual source of the area percent. The spectrometer is the source of the mass for a chosen peak. A total-ion chromatogram is not the same trace. Use the trace the report says it integrated.

The endotoxin line, when it exists

Bacterial endotoxin does not appear as a peptide peak. Limulus amebocyte lysate methods, and recombinant Factor C methods, are separate tests. The result is a number with a unit, often endotoxin units per milligram, per millilitre, or per vial. Copy the number and the unit. A purity percentage does not imply an endotoxin result, and an endotoxin result does not imply sterility. For the reading note, see endotoxin testing on peptide COAs.

On the BlueNex Labs library, reviewed September 26, 2026, some rows carry an endotoxin link and some do not. GHK-Cu 50 mg, batch HF1F6C9, has both a mass/purity link and an endotoxin link. Retatrutide 30 mg, pink cap, has a purity link and an endotoxin link. Write "endotoxin not on this report" only when that second link is absent. Do not copy the GHK-Cu endotoxin number across.

A pass over the PDF

Open the laboratory URL from the library. A photograph of a report is not the report. Check the sample name against the vial label before you read the percentage. Check the date and the task identifier in the URL so this file cannot be confused with an older upload. Then read the method line: column or technique, detector, and the integration rule if it is stated. Then the mass, including the species. Then the peak table. Then endotoxin, or an explicit note that it is absent. Then anything the report does not contain. Sterility, residual solvent, water content, and elemental impurities are common absences. A receiving log can list them as not reported.

The supplier page and the testing laboratory are different authors. BlueNex Labs hosts the library. The laboratory named on the PDF, often Janoshik for these lots, produced the chromatogram. A link on a catalogue page is not itself the data. The vial-to-PDF match, including cap colour, is how to verify a lot report against the vial.

Worked rows, not a universal template

Use three library patterns as examples of separate documents. The BPC-157 10 mg row pairs a mass/purity link with an endotoxin link for a blue-cap 10 mg vial. The GHK-Cu 50 mg row is a pair of links, mass/purity and endotoxin, for batch HF1F6C9. Retatrutide is three fills on three catalogue URLs: 10 mg blue cap at Retatrutide 10 mg and the Retatrutide 10 mg certificate, 20 mg purple cap at Retatrutide 20 mg and the Retatrutide 20 mg certificate, and 30 mg pink cap at Retatrutide 30 mg and the Retatrutide 30 mg certificate. Each fill has its own links. A blue-cap report does not document a pink-cap vial.

TB-500 10 mg publishes its purity file on the TB-500 10 mg certificate row. The published blend report at BPC-157 / TB-500 5 mg/5mg documents that blend lot, not the single-peptide TB-500 cake. The Hospira bacteriostatic water 30 mL listing has no published library row. A neighbouring peptide's PDF does not document that bottle, and the bottle has no Janoshik task identifier to record.

File the PDF with the storage record described in peptide storage for Canadian laboratories. The legal category of the solid is a different question, covered in are research peptides legal in Canada?. A matched COA does not change that category.

A purity percentage does not settle a viral outcome claim. That comparison is Viral Peptide Claims vs Evidence.

What the document is for

A peptide Certificate of Analysis records one lot. It is not a specification for every vial of that name, and it is not a Drug Identification Number.

Identity and purity answer different questions

Identity is the mass compared with the mass calculated for the named sequence. Purity, when the report means it, is a chromatographic area percent. A high area percent on the wrong mass is a different compound. Read both lines when the PDF prints both.

Endotoxin, sterility, and what is absent

Endotoxin is a separate test. Sterility, residual solvent, and water content are absent unless the PDF prints them. A missing line is not a passing line. Do not copy a number from a neighbouring lot to fill the gap.

Match the row to the vial

Library anchors follow the catalogue slug. Cap colour, milligram size, and the sample name must agree with the glass in hand. A blue-cap report does not document a pink-cap vial. The vial match is how to verify a lot report against the vial.

Frequently asked questions

Does an HPLC percentage identify the peptide?

No. The percentage is the area of the assigned peak divided by the areas the method integrated. Identity is the mass result, compared with the mass expected for that sequence.

What does a mass result add to a purity percentage?

It names the species that was weighed by the spectrometer. A high area percent on the wrong mass is a different compound. Read both lines when the report prints both.

Does a purity report include an endotoxin result?

Only when the laboratory ran that test and printed it. Endotoxin is not visible on a chromatogram. A missing line means the test was not reported for that lot.

Where is the shorter document primer?

What is a peptide COA in Canada explains what the document is for. This page reads the HPLC, mass, and endotoxin lines. The certificates library holds the live PDFs.

Catalogue cross-reference

Start from the certificates library. Shop examples used above are BPC-157 10 mg, GHK-Cu 50 mg, TB-500 10 mg, retatrutide, and Hospira bacteriostatic water.

Orders ship inside Canada only after Interac e-Transfer checkout. Sold-out SKUs remain listed and cannot be added to the cart. Match each vial to its own Certificate of Analysis when a lot is published. Research use only. Not for human or veterinary use.

Glossary notes for the words in this guide: analytical specification, impurity profile, and oxidation impurity.