How to read a peptide certificate of analysis
A peptide certificate of analysis tells you what the material is, how pure it is and which batch it came from — if you know where to look. This guide walks through the parts that matter and the warning signs.
What a certificate of analysis is
A certificate of analysis (COA) is the document a laboratory issues after testing a specific batch. It records the method used, the result and the batch it applies to.
A COA describes one batch. It is not a promise about every future batch, which is why the batch reference matters so much.
The four parts to check
- Batch reference — it must match the reference on the label of the vial you hold.
- Identity — usually a mass-spectrometry result showing the measured molecular mass against the expected value.
- Purity — usually an HPLC result stated as a percentage, with the method beside it.
- Laboratory and date — who did the analysis and when.
Reading an HPLC result
High-performance liquid chromatography separates a sample into its components as it passes through a column. The chart shows peaks, and the purity percentage is the area of the main peak as a share of all peaks.
A high percentage is only meaningful with the method beside it, because wavelength, column and gradient all change what appears. Two laboratories can report different figures for the same sample using different methods.
Reading a mass-spectrometry result
Mass spectrometry measures molecular mass. The measured value should match the calculated mass for the sequence within a small tolerance. If it does not, either the sequence is not what was ordered or the sample contains something else.
HPLC tells you how much of the sample is the main component; mass spectrometry tells you what that component is. Both are needed.
Purity is not the same as content
A purity figure describes the proportion of the main peptide among all peptide-related peaks. It does not describe how much of the vial contents is peptide, because lyophilised material also contains water and counter-ions such as acetate or trifluoroacetate.
Net peptide content, when reported, is the figure that tells you how much active sequence a milligram of powder contains. If a protocol depends on exact molar concentration, ask whether it is on the certificate.
Questions to ask any supplier
- Is the analysis done by an independent laboratory, and which method was used?
- Does the certificate carry a batch reference that matches the vial?
- Can I see the chromatogram and the mass spectrum, not only a summary?
- Will the same batch be available for a second order?
Warning signs
- No batch reference, or one that does not match your vial.
- A purity figure with no method.
- A certificate that has no laboratory name or date.
- Identical certificates for different compounds or strengths.
- A purity claim that has no document behind it.
Getting a certificate from us
Email support@eupeptidesciences.com with the compound name or the batch reference on your label, and the certificate covering that batch is sent to you. More on our testing is on the quality assurance page.
Peptide Certificate Of Analysis: quick reference
| Quick reference | Detail |
|---|---|
| Batch reference | Must match your vial label |
| Identity | Mass-spectrometry result |
| Purity | HPLC percentage with method |
| Laboratory | Named, with date |
| Warning sign | A purity figure with no method |
| Get a COA | support@eupeptidesciences.com |
The page for Peptide Certificate Of Analysis also covers storage, handling and the certificate of analysis, so nothing has to be requested twice.
Researchers comparing options for Peptide Certificate Of Analysis will find the neighbouring compounds linked below.
Questions about Peptide Certificate Of Analysis are answered by email, and the order ships once payment is confirmed.
Peptide Certificate Of Analysis: frequently asked questions
What does purity of 99% mean on a COA?
It usually means the main peak accounts for 99% of the total peak area in the HPLC chromatogram under the stated method. It does not describe water or salt content.
Why do two COAs for the same peptide differ?
Different methods, different batches or different laboratories give different results. Compare methods before comparing numbers.
Can a COA be faked?
Yes, which is why a batch reference matching your vial and a named laboratory matter.
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