Understanding peptide certificates of analysis

What a certificate of analysis is

A COA is a document issued alongside a batch of material recording the tests that were performed on it, the results obtained and the specifications those results were compared against.

The essential idea is traceability. A COA is meaningful when it can be tied to a particular batch, produced on a particular date, tested by a particular method. A document describing a compound in general rather than a batch in particular is a product description, not a certificate.

Fields that carry real information

Not every field on a certificate is equally informative. The ones that anchor the document to reality are the batch identifier, the analysis date and the method descriptions.

• Batch or lot number — ties the document to specific material and should match the vial label.
• Date of analysis and, where given, a retest or re-evaluation date.
• Product identity, including the sequence or a structural identifier where applicable.
• Chromatographic purity, with the method and detection wavelength stated.
• Mass spectrometry result, giving both the observed and the theoretical mass.
• Net peptide content, where determined, reported separately from purity.
• Appearance and physical form of the material.
• Water content and residual solvent or counter-ion content, where determined.

How to tell a real certificate from a template

The most common failure mode is not a forged document but a generic one: a certificate that describes the compound rather than the batch, reused across every shipment.

The practical test is whether the document contains anything that could only be true of one specific batch. Raw chromatograms and spectra are the strongest evidence, because they are difficult to generate generically and they let a reader check the stated integration rather than take it on trust.

Round numbers repeated across every batch, absent method details, missing dates, or a purity figure with no accompanying chromatogram are all reasons to ask for more.

• Does the batch number on the certificate match the vial label?
• Are raw chromatograms and spectra included, or only summary figures?
• Are method conditions stated in enough detail to be reproduced?
• Is the observed mass reported alongside the theoretical mass?
• Is the issuing party identified, and is testing in-house or independent?

In-house testing and third-party testing

In-house testing is performed by the manufacturer or supplier. Third-party testing is performed by an independent laboratory with no commercial interest in the result.

Neither is automatically invalid, and in-house data from a competent laboratory can be perfectly sound. The distinction matters for the level of independent assurance the document provides, and the certificate should make clear which one it is.

A claim of third-party testing should be traceable to a named laboratory and a report that can be requested. An untraceable claim provides no more assurance than no claim at all.

What a certificate cannot tell you

A COA describes the material as it was at the point of testing. It does not describe how the material was stored or transported afterwards, and it does not extend to the condition of the vial on arrival.

It also does not speak to suitability. Whether a given material is appropriate for a particular experiment depends on the requirements of that experiment, and no certificate can make that determination for you.

Documentation at Peptide Tactics

Peptide Tactics does not publish batch analytical data on its product pages, and this website deliberately makes no purity claims, certification claims or testing-laboratory claims that are not backed by a document.

Where documentation is available for a specific item, it can be requested directly. See the documentation page for how that request is handled and what to ask for.

Frequently asked questions

What should a peptide COA contain?

At minimum: a batch identifier that matches the vial, the date of analysis, product identity, chromatographic purity with method and detection wavelength stated, and a mass spectrometry result giving both observed and theoretical mass. Raw chromatograms and spectra add substantially to its value.

How can I tell whether a COA is batch-specific?

Look for information that could only be true of one batch — a batch number matching the vial, a specific analysis date, and raw chromatograms or spectra. A document that describes the compound in general terms without batch-specific data is a product description rather than a certificate.

Is third-party testing better than in-house testing?

Third-party testing provides independent assurance because the testing laboratory has no commercial interest in the outcome. In-house data from a competent laboratory can still be sound. What matters is that the certificate states clearly which one it is and that any third-party claim is traceable to a named laboratory.

Sources and further reference

• Lai M.C., Topp E.M. Solid-state chemical stability of proteins and peptides. Journal of Pharmaceutical Sciences, 1999 (PMID 10229638)
• Solid-state protein formulations. Therapeutic Delivery, 2015 (PMID 25565441)

Compounds this applies to

The considerations above are not abstract. Each of these compounds is listed in the Peptide Tactics catalog for research use in India, with its reference data, analytical notes and documentation status set out in full.

See the full research peptide catalog, the India sourcing guide or how to request documentation.

Continue reading

• Peptide purity explained — What a peptide purity percentage actually measures, why it differs from net peptide content, and which method details make a purity claim readable.
• HPLC analysis of peptides — How reversed-phase HPLC separates peptides, which method parameters change the reported purity, and how to read a peptide chromatogram critically.
• Mass spectrometry and peptide characterisation — How ESI and MALDI mass spectrometry confirm peptide identity, why average and monoisotopic masses differ, and which mass shifts are diagnostic.