How To Read
a Certificate
of Analysis
A certificate of analysis (COA) is a laboratory report on one specific batch of material. It typically reports purity by HPLC, identity by mass spectrometry, and physical characteristics. A COA speaks only to the batch tested — and only to purity and identity, not to safety or fitness for any purpose.
What a certificate of analysis is
A certificate of analysis is a report issued by an analytical laboratory describing what was found when a sample of a specific batch of material was tested. It is a factual record of measurements taken on one batch, on one date, by one laboratory.
The single most important thing to understand about a COA is its scope. It applies to the batch identified on the document and to no other batch. A COA from a previous batch tells you nothing about the material in front of you. This is why batch numbers on a vial and on the certificate must match.
Purity: the HPLC figure
Purity on a peptide COA is normally determined by high-performance liquid chromatography (HPLC). The technique separates the components of a sample as they pass through a column, and a detector records them as a series of peaks. The area under the main peak, expressed as a percentage of the total area of all peaks, is the reported purity.
A figure of, say, 99.1% means the target compound accounted for 99.1% of the detected material. The remaining fraction consists of related substances — typically truncated sequences, deletion sequences or other synthesis by-products. A well-formed COA shows the chromatogram itself, not just the number, so the peak shape and the size of any secondary peaks can be inspected directly.
Note that HPLC purity is a measure of chromatographic purity by peak area. It is not a statement about total mass, and it does not account for non-peptide content such as residual water or counter-ions unless those are separately reported.
Identity: mass spectrometry
Purity tells you how much of the sample is one thing. It does not tell you what that thing is. Identity is established separately, normally by mass spectrometry (MS).
Mass spectrometry measures the mass-to-charge ratio of the molecule. The observed mass is compared against the theoretical mass calculated from the expected amino acid sequence. If the observed and theoretical masses agree within the tolerance of the instrument, that is consistent with the sample being the compound it is claimed to be.
A certificate reporting purity but not identity is incomplete. High purity of an unidentified compound is not a meaningful assurance.
What else appears on a COA
- Batch or lot number — must match the vial.
- Test date and issuing laboratory — an independent third-party laboratory carries more weight than an in-house report.
- Appearance — typically described for a lyophilised peptide as a white to off-white powder or cake.
- Net peptide content — where reported, the proportion of the material that is peptide as opposed to water and salts. Distinct from chromatographic purity.
- Storage conditions — the conditions under which the stated characteristics are expected to hold.
What a COA does not tell you
This is the part most often misread. A certificate of analysis is a statement about purity and identity. It is not:
- An indication of safety.
- An indication of fitness for any particular purpose.
- An approval, licence or marketing authorisation of any kind.
- Any form of endorsement for use in humans or animals.
A compound can be 99.9% pure, correctly identified, and still be an unlicensed research chemical that has never been evaluated for safety in humans. Purity and safety are unrelated questions, and a COA answers only the first.
Requesting a COA
Every batch we supply is submitted for independent third-party analysis. The certificate for the batch you receive is available on request — send us the batch number printed on the vial and we will provide the corresponding certificate. Where a report is already published for a batch, it is linked directly from the product listing.
Frequently Asked Questions
A COA reports the results of laboratory testing on one specific batch of material. For peptides it normally reports purity determined by HPLC, identity confirmed by mass spectrometry, appearance, batch number, test date and the issuing laboratory.
No. Purity and safety are unrelated questions. A certificate of analysis reports purity and identity only. It is not an indication of safety, fitness for any purpose, or approval for use in humans or animals. A compound can be highly pure and still be an unlicensed research chemical that has never been evaluated for safety in humans.
A COA applies only to the batch it identifies. A certificate from a different batch says nothing about the material you hold. The batch number on the vial and on the certificate must match for the document to be meaningful.
HPLC purity is chromatographic purity by peak area — the proportion of detected material accounted for by the main peak. Net peptide content is the proportion of the total material that is peptide as opposed to water, salts and counter-ions. They measure different things and a sample can show high HPLC purity while having lower net peptide content.