A certificate of analysis (COA or CoA) is a document that records the laboratory tests performed on a specific batch of a material, the results obtained, the acceptance criteria (limits) those results were judged against, and whether the batch complied. In pharmaceutical manufacturing, COAs are a standard part of quality control. They matter just as much for anyone trying to understand the quality of a peptide sample. This guide explains what a COA should contain, which tests commonly appear on one for peptides, and what a COA can and cannot prove.
Key Takeaways
- According to WHO guidance, a COA lists the tests performed on a sample, the results, and the acceptance criteria, followed by a statement of whether the sample complies with the specification [1].
- A COA is usually prepared for each batch, so the batch number on the COA should match the material it describes [1].
- The ICH Q7 GMP guideline says COAs should list each test with its acceptance limits and numerical results, and should be dated and signed by authorized quality personnel [2].
- For synthetic peptides, typical tests include appearance, identity, purity, assay (content), counter-ion content, water content, residual solvents, and, where relevant, bacterial endotoxins [3].
- A COA is only as trustworthy as the laboratory, methods, and sample behind it.
Certificate of Analysis: The Basic Definition
The World Health Organization (WHO) publishes a Model Certificate of Analysis for quality control laboratories and for trade in pharmaceutical starting materials and finished products. First published in 2002 and updated in 2018, it explains that a COA "lists tests performed on a particular sample with the results obtained and the acceptance criteria applied, followed by an indication of whether or not the sample complies with the specification" [1].
Three terms are worth defining up front:
- Specification: the list of tests, methods, and acceptance criteria that a material must meet.
- Acceptance criteria: the numerical limits, ranges, or other measures a result must meet [4]. Example: "purity not less than 98.0%".
- Batch (or lot): a quantity of material produced in one process or series of processes, identified by a unique number.
What Should a COA Contain?
The WHO model and the ICH Q7 guideline on good manufacturing practice (GMP) for active pharmaceutical ingredients describe similar core elements [1][2]:
| COA element | Why it matters |
|---|---|
| Name and address of the issuing laboratory | Tells you who actually did the testing [1] |
| Unique COA identification number, with page numbering ("page X of Y") | Prevents pages from being mixed up or swapped [1] |
| Product name and description (including grade, where relevant) | Identifies what was tested [1][2] |
| Batch number | Links the results to one specific batch [1][2] |
| Date of manufacture (if available) and expiry or retest date | Shows the time window for which quality is supported [1][2] |
| Name and address of the original manufacturer (and any repacker or trader) | Supports traceability [1][2] |
| Test methods (e.g., pharmacopoeial references) | Shows how each result was obtained [1] |
| Acceptance criteria for each test | Shows what "pass" means [1][2] |
| Actual results, in numbers where applicable | Lets you see how close a result is to its limit [1][2] |
| Conclusion on compliance | States whether the batch met its specification [1] |
| Date and signature of an authorized person | Shows accountability [1][2] |
The WHO model also says that results from subcontracted laboratories should be identified as such, and that laboratories accredited to the ISO/IEC 17025 standard should reference the accreditation if it relates to the specific analysis [1].
A note on repacked or relabeled materials
Both WHO and ICH Q7 address a common situation: material that passes through repackers, agents, or brokers. If such parties issue new certificates, the certificates should show the name and address of the laboratory that performed the analysis and refer to the original manufacturer. A copy of the original manufacturer's COA should be attached [1][2].
Tests Commonly Found on a Peptide COA
The European Medicines Agency (EMA) guideline on synthetic peptides lists tests that a specification "may include" (a non-exhaustive list) [3]:
- Appearance: a description of the physical form and color
- Identification: confirms the molecule is the intended peptide. EMA recommends at least two orthogonal (independent) methods, such as mass, relative retention time, LC-MS, peptide mapping, amino acid analysis, or NMR
- Purity: total impurities and individual impurities, usually by liquid chromatography
- High molecular weight impurities: such as dimers or aggregates, where relevant
- Assay/content: how much peptide is present, for example by liquid chromatography against a reference standard, amino acid analysis, nitrogen analysis, or quantitative NMR
- Counter-ion identity and content: for example acetate, and residual trifluoroacetate (TFA)
- Water content
- Residual solvents and elemental impurities
- Bacterial endotoxins and microbiological purity
Each of these answers a different question. For a deeper explanation, see Identity vs. Purity vs. Quantity Testing, HPLC Testing Explained, Mass Spectrometry for Peptides, and Endotoxin and Sterility Testing.
How to Evaluate a COA: Questions to Ask
A COA is a claim. These educational questions can help you judge how much weight it deserves. For a step-by-step walkthrough of an actual report, see How to Read a Peptide Lab Report.
- Does the batch number match? A COA describes one batch [1]. A COA for a different batch, or one with no batch number, tells you little about the material in hand.
- Who performed the testing? Is the testing laboratory named, with an address? Are any subcontracted results identified [1]?
- Are there numerical results, or only "pass"? ICH Q7 expects numerical results where tests are numerical [2]. "Conforms" with no number hides how close a result was to its limit.
- Are acceptance criteria stated? A result of "97%" means little unless you know the limit was, for example, "not less than 95%".
- Are the methods identified? Purity results, for example, are method-dependent [4].
- Is identity actually confirmed? Purity alone does not prove identity. A high purity percentage could, in principle, belong to the wrong molecule.
- Is it dated and signed? Both WHO and ICH Q7 call for this [1][2].
- Are dates consistent? Check test date, manufacture date, and expiry or retest date.
What a COA Cannot Tell You
Even a complete, genuine COA has limits:
- It describes a sample, not every vial. Testing is performed on samples taken from a batch. The WHO model notes that sampling plans should be referenced where relevant to the validity of the results [1].
- It reflects the methods used. Different methods can give different results. ICH Q6B notes, for biotechnological products, that absolute purity is difficult to determine and results are method-dependent [4].
- It is a snapshot in time. Peptides can degrade during storage. The WHO model notes that certificates used in trade may state the shipping and storage conditions whose violation would invalidate the certificate [1].
- It is only as reliable as its issuer. A document can be incomplete, copied from another batch, or inaccurate. Independent verification and traceability matter.
Regulatory Status
COA requirements depend on the context and the jurisdiction. The ICH Q7 GMP guideline, developed through the International Council for Harmonisation, sets out expectations for certificates of analysis for active pharmaceutical ingredients [2], and national and regional regulators apply their own GMP rules. The WHO model COA also advises that any specific legal requirements in the country of issue or importation be considered [1].
Materials sold outside regulated medicinal product frameworks may not be subject to the same requirements, so the presence of a COA does not by itself indicate that a product meets pharmaceutical standards. See Research-Grade vs. Pharmaceutical-Grade.
Regulatory status varies by jurisdiction and may change over time. Consult the relevant regulatory authority for current information.
Frequently Asked Questions
What does COA stand for?
COA stands for certificate of analysis, a document reporting test results for a specific batch against defined acceptance criteria [1].
Is a COA the same as a lab report?
Not exactly. A full laboratory report may include raw data such as chromatograms and spectra. A COA is a summary certificate of tests, results, limits, and a compliance conclusion [1].
What is a good purity on a peptide COA?
There is no single universal number. The appropriate limit depends on the peptide and its intended use. What matters is that the result meets a justified specification, and that identity and content are also confirmed [3].
Can a COA be faked?
Documents can be falsified or reused. That is why checking batch numbers, testing laboratory details, signatures, dates, and numerical results, and seeking independent verification where appropriate, is important [1][2].
Why does a COA list water and counter-ion content?
Synthetic peptide powders can contain water and counter-ions (such as acetate or trifluoroacetate) as well as the peptide itself. EMA guidance expects these to be controlled [3].
References
- World Health Organization. Model certificate of analysis. WHO Expert Committee on Specifications for Pharmaceutical Preparations, Fifty-second report. WHO Technical Report Series No. 1010, 2018, Annex 4. https://www.who.int/publications/m/item/trs1010-annex4 ↗
- ICH. Q7: Good Manufacturing Practice Guide for Active Pharmaceutical Ingredients, section 11.4 (Certificates of Analysis). https://database.ich.org/sites/default/files/Q7%20Guideline.pdf ↗
- European Medicines Agency. Guideline on the Development and Manufacture of Synthetic Peptides (EMA/CHMP/CVMP/QWP/367182/2025), sections 4.4.1–4.4.2. https://www.ema.europa.eu/en/development-manufacture-synthetic-peptides-scientific-guideline ↗
- ICH. Q6B: Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products (sections 4.1.3 and 5, Glossary). https://database.ich.org/sites/default/files/Q6B%20Guideline.pdf ↗
Educational disclaimer: This article is for general educational purposes only. It is not medical, legal, or regulatory advice, and it does not recommend or evaluate any product or supplier. For health questions, consult a qualified healthcare professional. For regulatory questions, consult the relevant regulatory authority in your jurisdiction.