What a COA is for
A COA is a batch-specific record issued by the manufacturer or a testing laboratory. It links one batch (lot) of material to the tests performed on it and the results obtained. A COA describes a particular batch on particular dates. It is not a general product description, and a COA from one batch says nothing reliable about another.
The sections to check
1. Identification of the material and batch
The COA should name the material and give its sequence or structure, the batch or lot number, and the manufacture and test dates. The batch number should match the label on the vial and the invoice or packing list. If any of these are missing, the document cannot be tied to the material in front of you.
2. Who issued it
Look for the name and address of the issuing laboratory, the name of the person who approved the results, and a signature or electronic approval. If the COA comes from an independent laboratory, you should be able to contact that laboratory directly to confirm the report number.
3. Identity: mass spectrometry
Mass spectrometry (MS) confirms that the molecule has the expected mass. A useful COA reports both the theoretical mass calculated from the sequence and the observed mass, and ideally includes the spectrum. The observed value should agree closely with the theoretical value for the stated form of the peptide.
4. Purity: HPLC
High-performance liquid chromatography (HPLC) separates the target peptide from related impurities, such as truncated or modified sequences. Purity is usually reported as the percentage of the total peak area that belongs to the main peak. A reliable COA states the method (column, detection wavelength, gradient) and includes the chromatogram, so you can see the main peak and any impurity peaks for yourself.
5. Purity is not the same as peptide content
This is the most commonly misunderstood point. HPLC purity tells you what fraction of the peptide material is the correct peptide. It does not tell you how much of the powder's weight is peptide. Lyophilised peptides also contain counter-ions (often trifluoroacetate or acetate, left from synthesis and purification) and residual water. Net peptide content, often determined by amino acid analysis or nitrogen analysis, reports the percentage of the total weight that is peptide. A material can be 98% pure by HPLC and still have a net peptide content well below 100%.
6. Other results you may see
- Counter-ion content: the salt form and how much of it is present.
- Water content: often measured by Karl Fischer titration.
- Appearance: for example, white to off-white lyophilised powder.
- Solubility: a qualitative statement about the tested solvent.
- Endotoxin or microbial testing: relevant only where the research application requires it, and only meaningful if the method is stated.
Red flags
- No batch number, or a batch number that does not match the vial.
- Results without a method, or a purity figure without a chromatogram.
- Identical COAs (same results, same dates) supplied for different batches.
- Suspiciously round or perfect results, such as 99.99% for every product.
- An issuing laboratory that cannot be found or does not confirm the report.
- Signs of editing, such as mismatched fonts, misaligned numbers or missing pages.
How to verify a COA
Ask the supplier for the full report, including chromatograms and spectra. Contact the issuing laboratory to confirm the report number and batch. For critical work, consider sending a sample for independent identity and purity testing. Keep the COA with your laboratory records for the batch, so results can always be traced back to the material used.
How NEXA handles documentation
NEXA provides batch-specific documentation on request and does not publish purity or testing claims without supporting records. If you need a particular test, method or format, state it in your enquiry so it can be confirmed before any quotation.
Further reading
Storing and handling lyophilised peptides in the laboratory
Research materials
This article is general laboratory information for qualified research staff. It is not medical advice and does not describe human or veterinary use.