How to verify a peptide CoA (2026)

Introduction

A Certificate of Analysis (CoA) is the technical document accompanying each batch of a compound, summarizing the analytical tests applied. For a research peptide, the CoA is the basis of reproducibility across experiments: without it, there is no way to know what is being used.

This guide describes what a serious CoA must contain, how to read the HPLC chromatogram and mass spectrum, and which signals reveal documents that are altered, reused, or issued without real analysis.

What is a CoA

A CoA is the analytical summary of a batch. For a synthetic peptide, the minimum expected fields are: product identity, batch number, synthesis date, test date, sequence, theoretical and observed mass, HPLC purity, chromatographic method conditions, and the responsible analyst's signature.

The absence of any of these fields signals that the document was not issued by an analytical lab but written as a marketing piece. A real CoA is grounded in validation guidelines such as ICH Q2 ^[1], which describes acceptable parameters for identity, purity, and specificity of an analytical method.

Chromatogram reading

An HPLC chromatogram is a plot of absorbance (typically at 214 nm for the peptide bond) versus time. Each peak corresponds to a compound eluted from the column. In a pure peptide a single main peak should dominate, with a consistent retention time and minimal secondary peaks.

Purity is calculated as the area of the main peak divided by the sum of areas of all detected peaks. HPLC ≥99% means the main peak represents at least 99% of the total area. Reversed-phase methods with C18 columns and an acetonitrile / water + 0.1% TFA gradient are the standard for peptides ^[2].

Mass spectrometry

The mass spectrum confirms peptide identity. For a synthetic peptide, the observed mass (typically reported as M+H+ by ESI-MS) must match the theoretical monoisotopic mass calculated from the sequence. Acceptable tolerance depends on the instrument, but a difference greater than 1 Da in small peptides signals incorrect identity.

A serious CoA reports both theoretical and observed mass and ideally includes the full spectrum or attached images. If only the theoretical mass appears, there is no analytical confirmation of identity.

Batch and traceability

The batch number ties a specific vial to its analysis. Two vials from the same batch share a CoA; two vials from different batches require different CoAs. If a supplier sends the same PDF regardless of batch, there is no real traceability.

Re/Vida issues a per-batch CoA from CDMX, with the batch number printed on the vial label; the retention sample is held by the synthesizing lab for a minimum of two years and is available for re-analysis on request.

Red flags

Certain elements in a CoA or in the supplier's operations suggest an altered, pre-fabricated, or unsupported document. Catching them early avoids compromising an experiment with uncharacterized material.

• Same PDF with the same date sent for multiple batches.
• Generic chromatogram with no retention times or visible scale.
• Purity reported as ‘≥99%’ with no chromatogram and no area calculation.
• Theoretical mass without an observed mass, or both identical with zero decimals.
• No signature or no responsible analyst named.

Conclusion

Verifying a CoA is a basic analytical skill for peptide research. The key pieces are: a chromatogram with retention time and area calculation, an observed MS mass matching theoretical, a batch number tied to the physical vial, and a responsible analyst's signature. Without these four elements, the document is not a CoA, it is a brochure.

The compounds described in this guide are scientific research materials. They are not medications, supplements, or products for human consumption.