How to read a peptide Certificate of Analysis (COA)

How to read a peptide Certificate of Analysis (COA)

For research purposes only. Not for human consumption. 18+. UK only. This article is about laboratory analysis and document verification — how to read testing data, not how to use any compound.

What is a Certificate of Analysis?

A peptide Certificate of Analysis (COA) is a batch-specific laboratory document that proves what is actually in a vial. It reports the peptide's identity (by mass spectrometry) and purity (by HPLC), tied to a named batch number, a test date, and the testing laboratory. A genuine COA is issued by an independent lab that analysed a sample of the batch — not written by the seller.

That distinction is the whole point. Two vials with the same name on the label can differ substantially in purity, identity, and residual-solvent content. The COA is the only practical way for a research buyer to verify the material against the claim, batch by batch, before purchase.

This guide explains how to read a COA line by line, what HPLC and mass spectrometry each prove, how to independently verify a certificate, and how to spot a marketing document dressed up as one. It is written for the UK research community evaluating supplier quality.

What HPLC purity tells you

HPLC (High-Performance Liquid Chromatography) separates the components of a sample by pushing them through a column under high pressure. A detector records what elutes off the column over time, producing a chromatogram — a graph of peaks, each representing a distinct molecule in the sample.

For a research peptide, HPLC answers one question: of everything in this vial, what proportion is the target peptide? A credible COA reports:

• A purity percentage — the area of the target peptide peak as a proportion of total peak area. Research-grade peptides typically report ≥99%.
• The chromatogram itself — so you can see the main peak and the size and number of any impurity peaks.
• The method conditions — column type, mobile phase, gradient, flow rate, and detection wavelength — which document that the test is reproducible.

A bare number ("99.5% pure") without a chromatogram is weaker evidence than the same number shown with the trace. The chromatogram is what lets you distinguish a clean run with one dominant peak from a noisy run with several small impurity peaks that happen to sum to "99%."

What HPLC does not tell you is what the molecule is. A sample can be 99% one single, consistent compound — and that compound can be the wrong peptide. That is the job of mass spectrometry.

What mass-spectrometry identity confirmation proves

Mass spectrometry (MS) measures the mass-to-charge ratio of ionised molecules, which yields the molecular weight of the compound in the vial. For a peptide, MS confirms identity: it checks that the measured molecular weight matches the theoretical molecular weight calculated from the intended amino-acid sequence.

A credible COA reports:

• The expected (theoretical) molecular weight for the target peptide sequence.
• The measured molecular weight from the MS analysis.
• A match — for a correctly identified peptide the two agree closely, typically within about ±1 Da.

If the MS section is missing, or the measured mass is meaningfully off the theoretical value, the compound may be misidentified — a different peptide, or a sequence variant, of similar HPLC purity. This is uncommon in the credible supply chain, but it is exactly the failure HPLC alone cannot catch.

HPLC vs mass spectrometry — the short version

They answer different questions and a complete COA carries both:

• HPLC = purity. How much of the sample is the target peptide (a percentage).
• Mass spectrometry = identity. Whether the target peptide is actually the compound present (a molecular-weight match).

A number without an identity check is unverified; an identity check without a purity figure tells you nothing about impurities. Read both.

How to read each part of a COA

A complete single-peptide COA has the following fields. Use this as a checklist when a certificate lands in front of you.

The document should name the supplier, the independent laboratory that ran the analysis (with a website or contact details), and the product name. If no independent laboratory is named, it is not a third-party COA — it is a manufacturer's self-declaration.

HPLC purity (%)

The headline figure most readers look for first. Read it alongside the chromatogram and method conditions, as above. Research-grade material typically reports ≥99%.

Peptide content / mass

Purity and content are different measurements. Purity is the proportion of the material that is the target peptide; content (or mass) is how much peptide is actually in the vial — for example, a "10 mg" vial that assays at 10.93 mg. A vial can be highly pure yet under- or over-filled, so content is a separate quality signal worth reading. On multi-peptide blends there is often no single purity figure; instead the COA reports the mass of each component.

Batch / lot number

A COA is only meaningful if it is tied to a specific manufacturing batch. The batch number on the certificate should match the batch number on the vial you receive. A "generic" certificate not tied to any batch is not a COA.

Test date

Analysis reflects the batch that was tested. A test date should be recent enough to correspond to the inventory currently shipping — a certificate from three years ago tells you nothing about today's batch.

Laboratory and task/reference number

A credible lab assigns each analysis a unique task or report number. That number is what makes the certificate independently checkable — it is the key you use to look the report up on the laboratory's own system rather than trusting the PDF a seller sends you.

Additional analyses (optional but useful)

Higher-rigour COAs may also report water content (Karl Fischer titration), residual solvents (e.g. trifluoroacetic acid, a common synthesis residue), peptide content by amino-acid analysis, or endotoxin testing. None are mandatory for a basic research-grade COA, but their presence signals a more thorough testing regime.

Signature and dating

A real COA is signed by the analyst, dated, and on the laboratory's letterhead. Anonymous, unsigned, or undated certificates are weaker evidence.

How to independently verify a COA

A PDF emailed by a seller proves nothing on its own — it can be edited, recycled across batches, or fabricated. Independent verification means confirming the certificate against a source the seller does not control:

1. Confirm the laboratory is independent. The lab that signed the COA should be a third party, not the supplier or its own manufacturer.
2. Look the report up at the lab, not the seller. Reputable analytical labs publish per-report verification pages keyed to the task/report number. Enter that number on the laboratory's own site and confirm the purity, content, and identity figures match the PDF you were given. A certificate whose laboratory cannot be cross-referenced is not a verified document.
3. Match the batch. Check the batch number on the certificate against the batch number printed on the vial. A QR code on the vial that links straight to that batch's report is the strongest form of this check.
4. Check the date. Confirm the test date corresponds to current inventory, not a legacy batch.

If all four hold, you are looking at a verified certificate. If the laboratory is unnamed, the report number returns nothing, or the batch does not match, treat the material as unverified regardless of how the PDF looks.

Why independent testing matters for research materials

Independent, batch-level testing exists because self-reported quality cannot be checked. A supplier testing its own product — or publishing a certificate with no named lab — has both the means and the incentive to present a favourable result. Independent laboratory testing of peptide products has historically surfaced:

• Actual purity well below the claimed figure, sometimes by tens of percentage points.
• Misidentified compounds — the wrong peptide, or a different sequence variant.
• Detectable residual solvents from incomplete purification.

A COA from an independent third-party laboratory, tied to the specific batch being sold and checkable against that lab's own records, is the standard the research community uses to filter for credible suppliers. It converts "trust us" into "check for yourself."

Red flags — when a "COA" isn't really a COA

• No batch number. A generic certificate not tied to a batch is not a COA.
• No independent laboratory named. Self-issued, with no third party to hold accountable.
• Only a percentage, no chromatogram. The number alone is not verifiable.
• No mass-spectrometry result. Identity is unconfirmed.
• Test date older than ~12 months. Stale data does not represent current stock.
• No method conditions. Reproducibility can't be assessed.
• Report number that can't be looked up at the lab. No independent check.
• COA only shared after purchase. Gating verification past the buying decision is a design choice, not an accident.

How BioHack London tests every batch

BioHack London tests every batch through Janoshik Analytical, an internationally established third-party analytical laboratory widely used across the research-supply sector. Each batch is analysed by HPLC for purity and mass spectrometry for identity, and the resulting certificate is published — not held back until after purchase.

Those certificates are collected in a public library on the Lab Test Reports page, each card carrying the purity figure, measured content, batch, test date, Janoshik task number, and a link to Janoshik's own verification page so any reader can cross-reference the result independently. Recent published examples include BPC-157 at 99.635% HPLC purity, GHK-Cu at 99.912%, and TB-500 at 99.102% — each verifiable against Janoshik's records by its task number.

This is the bar BioHack London operates to: independent lab, both tests, per-batch certificate, published before purchase, and independently checkable. Many UK research-peptide suppliers do not clear it.

Frequently asked questions

What is a Certificate of Analysis for a peptide?

A peptide Certificate of Analysis (COA) is a batch-specific laboratory document confirming a peptide's identity and purity. It reports HPLC purity, mass-spectrometry identity confirmation, the batch number, and the test date, and is issued by the laboratory that analysed the sample — ideally an independent third party rather than the seller.

What is the difference between HPLC and mass spectrometry on a COA?

HPLC measures purity — what proportion of the sample is the target peptide, reported as a percentage from a chromatogram. Mass spectrometry confirms identity — that the compound's measured molecular weight matches the theoretical weight for the intended sequence. HPLC tells you how much target peptide is present; mass spectrometry tells you whether it is the right one. A complete COA carries both.

What purity should a research peptide COA show?

Most reputable UK suppliers report ≥99% HPLC purity for research-grade peptides. Read the figure alongside the chromatogram and method conditions rather than on its own — a percentage without a visible trace is weaker evidence.

How do I verify a peptide COA is genuine?

Confirm an independent laboratory is named, then look the report up using its task/reference number on that laboratory's own verification site and check the figures match the PDF. Match the batch number on the certificate to the batch on the vial, and confirm the test date reflects current stock. A certificate that can't be cross-referenced at the lab is not verified.

What is the difference between purity and content on a COA?

Purity is the proportion of the material that is the target peptide (a percentage). Content is how much peptide is actually in the vial (a mass, e.g. 10.93 mg in a 10 mg vial). A vial can be highly pure but under-filled, so the two are separate quality signals and both are worth reading.

Can a Certificate of Analysis be faked?

In principle, yes — a PDF can be edited or recycled. The defences are independent third-party testing, batch-specific certificates that match the vial, and a report number you can look up on the laboratory's own system. A COA you can verify at the lab, rather than only in the seller's PDF, is the one that resists fabrication.

What to do next

Three checks if you are evaluating a COA right now:

1. Confirm an independent third-party laboratory is named — not just the supplier.
2. Confirm HPLC purity (with chromatogram) and mass-spectrometry molecular weight are both present.
3. Take the report/batch number and verify it against the laboratory's own records, and match the batch to the vial.

If all three hold, you are looking at a credible, verifiable COA. For the distinction between tested and verified, see our reference guide on independently verified UK research peptides, or browse the full Lab Test Reports library.

About BioHack London. BioHack London is a UK-based supplier of research peptides. Every batch is independently HPLC- and mass-spectrometry-tested by Janoshik Analytical and published as a Certificate of Analysis, accessible before purchase and via QR code on the vial. For research purposes only. Not for human consumption. 18+.

Disclaimer. This article describes the technical content and verification of a peptide Certificate of Analysis for the UK research community. It does not constitute medical, legal, or regulatory advice. The compounds referenced are sold and intended for in vitro laboratory research use only — not for human or veterinary use, and not for the diagnosis, treatment, cure, or prevention of any disease.

References (selected).

• Snyder, L.R., Kirkland, J.J., Dolan, J.W. (2010). Introduction to Modern Liquid Chromatography, 3rd Edition. Wiley.
• de Hoffmann, E., Stroobant, V. (2007). Mass Spectrometry: Principles and Applications, 3rd Edition. Wiley.
• ICH Q3C (R8) Guideline on Residual Solvents — relevant to TFA testing and limits.