Semaglutide COA: verifying identity, purity and content
Semaglutide's side chain makes it harder to characterise than a plain peptide, and that raises the bar for what its certificate of analysis should show.
Research use only. Every compound referenced here is a laboratory reference material supplied to qualified researchers and institutional laboratories. None are medicines, supplements or consumer products, and none are for human consumption.
Semaglutide is a 31-residue GLP-1 analogue with a molecular weight of about 4113 Da and a fatty-acid side chain that extends its half-life. The modification is the reason the compound cannot be characterised by a purity percentage alone.
A complete semaglutide COA shows three separate things: that the material is the acylated peptide, that it is clean, and that the vial contains the quantity stated on the label.
Mass spectrometry is the identity check that counts
Because the side chain contributes a defined mass, the observed molecular ion on a semaglutide certificate should match the theoretical mass of the acylated construct. A mass consistent with the unmodified backbone is a warning sign: it can indicate a different analogue or an incomplete synthesis step.
Look for the measured mass, the theoretical mass and the ionisation mode used, so the comparison can be reproduced.
Purity and related substances in an analogue
Reverse-phase HPLC separates semaglutide from deletion sequences, diastereomers and oxidation products. The certificate should report the main peak and, ideally, the total related-substance figure against a stated specification.
An HPLC trace is more informative than a rounded number. It shows retention time, peak symmetry and whether small shoulders were included in the integration, which is where optimistic purity figures usually hide.
Peptide content and the labelled mass
As with any lyophilized peptide, the mass on the label refers to the peptide, while the powder includes counter-ions, buffer components and residual moisture. A certificate that reports peptide content lets a laboratory correct its concentration calculation instead of assuming the label equals the peptide mass.
Checks before the vial enters a study
A short verification routine catches most documentation problems:
- Match the lot code on the certificate to the code on the vial label
- Confirm the certificate names semaglutide and states the acylated theoretical mass
- Confirm both a purity result and mass data are present
- Check the analysis date — a certificate should belong to the lot, not an earlier campaign
- Record the storage conditions stated for that lot alongside the batch record
What a COA cannot tell you
A certificate of analysis is a statement about identity, purity and quantity at the time of testing. It is not a sterility certificate unless sterility testing is specifically reported, it is not a stability study, and it is not a safety or efficacy assessment.
Semaglutide is an approved drug substance in several markets, so research supply is subject to scrutiny. Every compound in this catalog is a laboratory reference material, sold to qualified researchers and institutions, and not for human consumption.
Common questions
What should a semaglutide COA report that a simple peptide COA does not?
The theoretical and measured mass of the acylated construct. Without the side-chain mass accounted for, the identity check is incomplete.
Is 99% HPLC purity sufficient on its own?
No. Purity describes how much of the detected material is one substance; it does not confirm which substance. Mass-spectrometry data is required for identity.
How is semaglutide shipped and stored?
Sealed lyophilized vials are dispatched cold-chain and held at −20 °C, protected from light. Reconstituted working solutions are stored at 2–8 °C per the handling note for that lot.
Are semaglutide certificates published per lot?
Yes. Each lot is independently assayed and its certificate is published in the COA directory against the lot code on the vial.