How to Read a Peptide COA: HPLC Purity, Mass Spec Identity and Verification

By Peptides & Coffee · Updated Oct 8, 2026 · About 9 minutes

Short answer: what does COA mean?

COA stands for certificate of analysis: a report from a testing laboratory that lists the analytical results for one specific lot (batch) of a material. For a research peptide, the core results are HPLC purity (how much of the detected material is the target peptide), mass spectrometry identity (whether the molecule has the expected molecular mass), the lot number, the test date and the lab's name and verification code. A COA tells you about one tested sample from one lot, nothing more.

The parts of a peptide COA

Layouts differ between laboratories, but almost every peptide certificate of analysis contains the same building blocks. Learn to find these and you can read any of them:

Laboratory header: the lab's name, address or website, and often a logo, a report or task number, and accreditation marks.
Client and sample information: who sent the sample (the client), the sample name as declared by the client, the lot or batch number, and the dates the sample was received, analyzed and reported.
Results table: each test performed, the method used, the specification (the pass limit, if one was set) and the result. For peptides this usually means identity, purity and sometimes quantity.
Raw data: an HPLC chromatogram (a trace of detector signal against time) and, where identity was tested by mass spectrometry, a mass spectrum.
Sign-off and verification: the analyst or reviewer's name and signature, and a unique code, key or QR code that lets anyone look up the same report on the lab's own website.

A useful habit is to read a COA in this order: who tested it, which lot it covers, when it was tested, what was tested and how, what the results were, and whether the lab's own record matches.

HPLC purity: what the percentage means

High-performance liquid chromatography (HPLC) separates the components of a sample as it is pushed through a packed column. For peptides, labs almost always use reversed-phase HPLC: a non-polar column with a water/acetonitrile mobile phase, usually containing a small amount of acid such as trifluoroacetic acid (TFA) or formic acid. Different molecules leave the column at different times, called retention times, and a detector records each one as a peak.

The most common detector is UV absorbance at about 210–220 nm, where the peptide bond itself absorbs light. That's why you will often see a line like "Sig=220 nm" or "UV 214 nm" on the chromatogram.

The purity percentage is normally an area percent: the area of the main peak divided by the total area of all integrated peaks, times 100. A result of "99.2% (HPLC)" means that, of everything the UV detector saw under those conditions, 99.2% of the signal came from the main peak.

What that number does not tell you matters just as much:

It's relative, not absolute. Area percent says nothing about how many milligrams are in the vial.
It only counts what the detector sees. Water, salts and counter-ions (such as acetate or TFA) barely absorb at 220 nm, so they don't show up in the purity figure even though they are part of the powder's weight.
It depends on the method. A short gradient or a poorly resolving column can hide impurities under the main peak. Two labs can report slightly different purities for the same material.
It doesn't prove identity. A perfectly pure sample of the wrong peptide can still read 99%. That's why identity testing is a separate result.

When a chromatogram is included, look for one dominant, reasonably sharp peak and a flat baseline. Small peaks near the main one are typically related impurities from synthesis or storage: deletion or truncated sequences (a missing amino acid), incompletely removed protecting groups, oxidation (for example of methionine) or deamidation (of asparagine or glutamine). Many labs list each impurity peak with its retention time and area percent.

Specifications in this market are commonly written as "≥98%" or "≥99%" HPLC purity. Read a specification as the pass line the vendor or lab set, and the result as the measurement.

Mass spectrometry: confirming identity

Mass spectrometry (MS) measures the mass-to-charge ratio (m/z) of ionized molecules. It answers a different question from HPLC: is this the molecule it's supposed to be? Every peptide sequence has a calculable theoretical molecular weight, and the lab compares the measured mass with that value.

Two ionization techniques are common:

ESI (electrospray ionization), usually coupled directly to HPLC as LC-MS. Peptides pick up several protons, so you see a series of peaks such as [M+2H]²⁺ and [M+3H]³⁺. Software "deconvolutes" these into a single neutral mass.
MALDI-TOF, which mostly produces singly charged [M+H]⁺ ions and is handy for a quick mass check.

When reading the identity line, look for the observed mass, the expected (theoretical) mass, and whether they agree within the lab's stated tolerance. Check whether the lab quotes monoisotopic or average mass: for a 1,400 Da peptide those differ by roughly one dalton, which is normal, not an error.

Know the limits of MS identity too. A mass match confirms composition, not order: a scrambled sequence with the same amino acids has the same mass. Tandem MS (MS/MS), which breaks the peptide into fragments, or comparison with a reference standard is needed to confirm sequence. Some COAs report identity by HPLC retention time against a reference standard instead of by MS. That is a valid check, but it isn't the same thing, so note which method the lab actually used. A COA that simply says "Identity: Conforms" without naming a method or showing data tells you less than one that shows the spectrum.

Purity vs. quantity vs. net peptide content

These three numbers are easy to mix up:

Purity (HPLC area %): the share of UV-detected material that is the main peptide.
Quantity or measured content (mg per vial): how much peptide the lab measured in the vial, usually by HPLC against a calibrated reference standard. Some labs test several vials and report each one, a mean, a standard deviation (SD) or a relative standard deviation (%RSD). A low %RSD means the vials were consistent with each other.
Net peptide content (%): the share of the powder's total weight that is actually peptide, as opposed to water and counter-ions. It's measured by methods such as amino acid analysis or elemental (nitrogen) analysis. For lyophilized peptide salts it is often well below 100%, commonly somewhere around 60–90%.

So a vial can be 99% pure by HPLC and still contain less than its labeled amount of peptide, or more. If quantity matters to your research, look for a measured-content result, not just purity.

Lot numbers and test dates

A lot (or batch) number identifies one production run. Peptides are synthesized, purified and freeze-dried in batches, and every batch can differ. A COA therefore applies only to the lot printed on it. The most important single check you can make is simple: the lot number on the COA must match the lot number on the vial label. A COA for "BPC-157" in general, with no lot number, is a marketing document, not a test result.

Pay attention to which date is which: the received date (when the lab got the sample), the analysis date and the reported or published date. They should appear in a logical order, and none should be in the future. A COA from several years ago may be genuine, but it describes a lot that is probably no longer on sale.

Who did the testing: labs and accreditation

A third-party COA comes from a laboratory independent of the manufacturer and seller. An in-house COA comes from the manufacturer's own quality-control lab. Both can be accurate, but a third-party report that you can look up on the lab's own website is much harder to fake.

The most widely recognized quality standard for testing labs is ISO/IEC 17025 (general requirements for the competence of testing and calibration laboratories). Accreditation to it is granted by an accreditation body (in the US, for example, A2LA or ANAB) and is scope-specific: it covers particular methods and analytes. If a lab claims accreditation, its certificate and scope should be public on the accreditation body's website. Check that the scope includes the tests on your COA. Not every lab working in this field is accredited, and "certified" or "GMP" logos on a COA are not the same as 17025 accreditation.

Other tests you may see

Endotoxin (LAL test): measures bacterial endotoxin with the Limulus amebocyte lysate assay (USP <85>), reported in EU/mg or EU/mL, or as pass/fail against a limit.
Heavy metals / elemental impurities (ICP-MS): typically arsenic, cadmium, lead and mercury, reported against limits.
Microbial screening: culture-based counts or PCR detection of microbial DNA.
Residual solvents (GC) and counter-ion content (for example TFA or acetate): leftovers from synthesis and purification.
Water content (Karl Fischer) and appearance (for example "white lyophilized powder").

Extra tests are a plus, but only if they were run on the same lot and appear in the lab's own record.

How to verify a COA

Find the lab's verification code. Labs print a unique code, key, accession number or QR code on each report.
Go to the lab's website yourself. Type the lab's address into your browser rather than trusting a link or QR code printed on the document; a forged COA can carry a forged link.
Enter the code in the lab's lookup. A real record should open on the lab's own domain.
Compare every field. Client, sample name, lot number, dates, purity, identity and quantity should all match the copy you were given. Any difference means the copy has been altered or belongs to a different sample.
Match the lot to your vial. Even a genuine COA proves nothing about a vial from another lot.

Every lot page in our COA hub puts the lab's verification code and a direct link to the lab's record right at the top, so you can do this in under a minute.

Red flags of a fake or altered COA

No lot number, or a generic one ("Batch 001") reused across products or years.
The lot on the COA doesn't match the lot on the vial.
No lab name, or a lab you can't find online, or no way to look up the report on the lab's own site.
The verification code doesn't work, or the lab's record shows a different client, sample, lot or result.
The "lab" website domain differs from the lab named on the report, or the link goes to the seller's own site.
Purity of exactly 100.00%, or suspiciously round figures across many lots.
Identical chromatograms (same peaks, same noise) on COAs for different lots or different peptides.
Identity stated as "pass" with no method and no observed mass, or a mass that doesn't fit the peptide.
Dates out of order (analyzed before received) or in the future.
Mismatched fonts, blurred or pasted-in numbers, cropped headers, or a seller watermark covering key fields.
A manufacturer's own letterhead presented as "independent third-party testing".

Check a real COA now

Search our COA hub by lot number and open each lab's own verification record.

Browse the peptide COA hub →

FAQ

What does COA mean for peptides?

COA means certificate of analysis. It is a laboratory report listing the test results, such as HPLC purity and mass spectrometry identity, for one specific lot of a peptide, along with the lab's name, the test date and usually a code to verify the report on the lab's website.

Is a certificate of analysis the same as a certificate of authenticity?

No. A certificate of analysis reports measured test results for a specific lot. A certificate of authenticity is a general statement that an item is genuine and contains no analytical data.

What does HPLC purity mean on a COA?

It is the area of the main peptide peak as a percentage of all peaks detected by HPLC, usually with UV detection at about 210 to 220 nm. It is a relative measure: it does not count water or salts and does not confirm which molecule the main peak is.

Does 99% purity mean 99% of the vial is peptide?

No. HPLC purity is a share of UV-detected material. The powder also contains water and counter-ions, so net peptide content by weight is usually lower. The amount in the vial is a separate quantity or content result.

What does mass spec identity confirm?

Mass spectrometry confirms that the measured molecular mass matches the theoretical mass of the expected peptide. It confirms composition but not amino acid order; tandem MS or a reference standard is needed to confirm sequence.

How do I verify a peptide COA?

Find the verification code, key or accession number on the COA, type the lab's website address yourself, enter the code in the lab's lookup, and check that the client, lot number, dates and results match your copy and your vial label.

Why must the lot number match my vial?

Each lot is a separate production batch with its own results. A COA only describes the lot it was issued for, so a COA for a different lot tells you nothing about your vial.

What is an ISO/IEC 17025 accredited lab?

It is a testing laboratory that an accreditation body has assessed as competent to perform specific tests under the ISO/IEC 17025 standard. Accreditation is limited to a defined scope of methods, so check that the scope covers the tests on the COA.

This guide explains how to read analytical chemistry documents. It is not advice on using any product. Products referenced on this site are for laboratory research use only and are not for human or veterinary consumption.