What Is a Certificate of Analysis?

A Certificate of Analysis (COA) is the primary quality document that accompanies a batch of research peptide. It summarizes the analytical testing performed on the batch and provides the data that researchers need to verify the material's purity, identity, and content. For anyone working with research peptides in a laboratory setting, knowing how to read and interpret a COA is an essential skill.

This guide walks through each section of a typical COA, explains what the data means, and highlights the key things to look for when evaluating a peptide supplier.

Product Identification

The top of a COA should clearly identify the product. At minimum, this section includes:

• Product name — The common or catalog name of the peptide (e.g., Ipamorelin, GHK-Cu)
• Amino acid sequence — The full sequence using one-letter or three-letter amino acid codes
• Catalog number or SKU — The supplier's internal product identifier
• Batch number — A unique identifier linking the vial to its production batch

If the amino acid sequence is not listed on the COA, this is a significant gap. The sequence is what allows a researcher to confirm that the peptide matches what was ordered, and it is essential for publication-quality record-keeping.

Purity by HPLC

Purity is the most commonly cited quality metric for research peptides, and it is measured by High-Performance Liquid Chromatography (HPLC). The COA should report the purity as a percentage, typically determined by reversed-phase HPLC with UV detection at 214 nm.

Research-grade peptides should generally meet or exceed 99% purity. The COA should include the HPLC chromatogram — a graph showing the separation of the peptide from its impurities. When reviewing the chromatogram, look for:

• A single dominant peak representing the target peptide
• Minimal small peaks (impurities) at other retention times
• A sharp, symmetrical peak shape
• A retention time that is consistent with the product specification

If the purity is reported as a number without a chromatogram, you may request the full chromatogram from the supplier. Reputable suppliers provide this documentation readily.

Identity by Mass Spectrometry (LC-MS)

While HPLC tells you how pure the sample is, it does not confirm that the peptide is the correct one. Mass spectrometry (typically LC-MS) provides this confirmation by measuring the molecular weight of the peptide and comparing it to the theoretical weight calculated from the amino acid sequence.

The COA should report both the calculated molecular weight and the observed molecular weight. These should match within the instrument's mass accuracy specification. A significant discrepancy suggests a synthesis error, a wrong sequence, or an unexpected modification.

The mass spectrum itself may also be included, showing the molecular ion peak. For larger peptides, the spectrum may show multiply-charged ions, which are used to calculate the actual molecular weight through deconvolution.

Net Content and Physical Properties

The net content section reports the actual mass of peptide in the vial. This is important because the gross weight of the lyophilized powder includes not just the peptide but also counter-ions (such as TFA or acetate salts) and residual moisture. A vial labeled as containing 5 mg of peptide should have 5 mg of actual peptide content, not 5 mg of total powder.

The COA should also describe the physical appearance of the product. Lyophilized peptides are typically white or off-white powders. Any discoloration or unusual appearance should be noted and investigated.

Storage and Stability Information

The COA should include recommended storage conditions, typically -20°C for lyophilized peptides in a frost-free environment. It may also include a retest or expiry date, indicating how long the peptide is expected to remain within specification under proper storage conditions.

Always follow the storage recommendations on the COA. Improper storage can degrade even a high-quality peptide, leading to unreliable experimental results.

Batch Traceability

The batch number on the COA is your link to all the analytical data for that specific production run. Always record the batch number in your laboratory notebook when you receive a new vial. If you need to repeat an experiment, you can use the batch number to verify that you are using material from the same production run, or to compare analytical data across batches.

For publication, many journals now require detailed information about reagent sources and batch numbers. Having this information readily available streamlines the manuscript preparation process.

Red Flags to Watch For

When reviewing a COA, the following issues should prompt further investigation:

• Missing chromatogram — A purity number without supporting data is difficult to verify
• Missing mass spectrometry data — Purity without identity confirmation is incomplete
• No batch number — Without traceability, quality claims cannot be independently verified
• Unusual purity values — Purity reported as exactly 100.0% or with excessive precision may indicate fabricated data
• No test date — Without a test date, the age of the data is unknown

Conclusion

A Certificate of Analysis is more than a formality — it is the documentary evidence that a research peptide meets the quality standards required for reliable laboratory work. By understanding how to read a COA, researchers can make informed decisions about their materials, maintain better laboratory records, and produce more reproducible results.

Healthy Peps provides available COAs through our lab results database, searchable by product and batch number. For a broader overview of peptide quality standards, see our research peptides Canada guide.