Peptide COA, HPLC and MS explained

How to read a peptide certificate of analysis: what each field means, what HPLC and MS measure, and what neither test can tell you.

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The COA

Read it field by field.

A certificate of analysis summarizes test results for one lot. Each field answers a question; check them in this order.

Lot number	Matches the quotation and, on delivery, the label
Product & strength	Same compound name and amount per vial as ordered
Dates	Manufacturing, test and retest dates are present and plausible
Specification	The limit the lot had to meet, e.g. a minimum HPLC purity
Result	The measured value, which meets the specification
Method	Which test produced each result (HPLC, MS, others)
Issued by	In-house QC or an outside laboratory, and who approved it

The two core tests

HPLC measures purity. MS confirms mass.

HPLC: purity

High-performance liquid chromatography separates the sample into its components. Purity is the main peak’s share of the total peak area at the detection wavelength.

The result meets the stated specification
The method or wavelength is named
If you have the chromatogram: one dominant peak, with small, separated impurity peaks

MS: identity

Mass spectrometry measures the mass of the molecule. The observed molecular weight should match the theoretical value for the sequence within the method’s tolerance.

Both the expected and the observed mass are stated
The difference is within the stated tolerance
If you have the spectrum: the main signal sits at the expected mass

Limits

What HPLC and MS don’t show.

These are separate questions with separate tests. If they matter for your work, add them to your own test panel.

Peptide content. HPLC area % is not the amount of peptide in the vial; water, counter-ions and salts are not counted.
Fill weight per vial.
Sterility and endotoxin.
Isomers of equal mass. MS confirms molecular weight; it can’t tell apart sequences with the same mass.
Biological activity or suitability for any use.
Safety data. An SDS covers handling and transport, not purity.

Who issued it

In-house QC or third party.

A COA may come from the manufacturer’s QC lab or from an outside laboratory. Both are valid records of different kinds. A third-party report is most independent when you chose the lab and took the sample yourself.

SeqLine Bio public COAs are in-house QC records. Each reproduces the HPLC purity and MS molecular-weight identity results from the source COA held in our quality records. Our release specification is NLT 98.0% by HPLC; the actual result is on each record.

FAQ

Questions buyers ask.

Are COA, HPLC and MS the same document?

No. The COA summarizes results for one lot. HPLC and MS are two of the tests behind it. Their results usually appear on the COA even when the chromatogram and spectrum are not attached.

Which field matters most?

The lot number, because every other field only counts if it describes your lot. Then the result against the specification, and the MS identity.

Does a high HPLC purity prove peptide identity?

No. HPLC shows how much of the sample is the main component, not what that component is. The MS molecular-weight result addresses identity.

Are SeqLine Bio’s public COAs third-party lab reports?

No. Each public record reproduces the source COA held in SeqLine Bio quality records. Independent testing by the buyer is welcome, and a confirmed quality issue is replaced or refunded under the quality policy.

Do the public COAs include the raw chromatogram or mass spectrum?

Not necessarily. The public record reports the results from the source COA. A separate chromatogram or spectrum is referenced only when that file exists; ask for it with your RFQ if you need it.

Next step

Send your compound list and document requirements.

We reply within 4 business hours with price, lead time and the COA for the lot you would receive.

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