A certificate of analysis is a document that reports the results of named tests, run on a sample from one production lot, on a stated date. That is exactly what it proves, and it is a narrower statement than most readers take from it.

This article covers what a certificate establishes, five things it cannot, and what closes each gap. For a field-by-field walkthrough, see our guide to reading a certificate of analysis.

All Janera Science compounds are supplied strictly for in-vitro laboratory research use only. They are not intended for human or veterinary use, and are not intended to diagnose, treat, cure, or prevent any disease. The statements made on this website have not been evaluated by the U.S. Food and Drug Administration.

What a Certificate of Analysis Is

A certificate of analysis (COA) is a batch-level record of test results. The international good manufacturing practice guide for active pharmaceutical ingredients (APIs) says it should name the material, its batch number and its date of release, and list each test performed with its acceptance limits and, where results are numerical, the numerical results obtained (International Council for Harmonisation, 2000).

That guide is written for manufacturers of active ingredients used in human medicines, and it serves here as a benchmark. Its acceptance limits come from a specification, which the same guidance defines as a list of tests, references to analytical procedures, and appropriate acceptance criteria (International Council for Harmonisation, 2000). The specification says what the material should be. The certificate says what one lot was found to be, for the tests on that list.

A certificate of analysis and a certificate of conformance

A certificate of conformance is a signed statement that goods meet requirements. In the certificate wording prescribed by a federal procurement clause, a contractor certifies that supplies are of the quality specified and conform in all respects with the contract requirements, and that wording contains no test results (Federal Acquisition Regulation 52.246-15, 1984).

A certificate of analysis, by contrast, puts numbers on the page that can be compared across lots and checked against the method that produced them.

What a Certificate of Analysis Establishes

A certificate of analysis establishes four things together: the result of each listed test, for one lot, measured on a sample, on one date. Each of those four boundaries is also where its evidence stops.

One lot

A batch, or lot, is a quantity of material produced so that it is expected to be homogeneous within specified limits, and its lot number is the identifier from which its production and distribution history can be determined (International Council for Harmonisation, 2000). The lot number connects the results to one run of material, and only to that run.

One sample

Manufacturing guidance says samples should be representative of the batch they are taken from, and that sampling methods should specify how many containers are sampled and how much is taken from each (International Council for Harmonisation, 2000). A result applies to other vials from the same lot by inference, which holds when the lot is homogeneous and the sample representative. The result itself demonstrates neither.

One date

A certificate records the material's state on the day it was tested. A retest date is defined as the date when a material should be re-examined to ensure it is still suitable for use, and for an API or intermediate assigned one, the guidance says it should appear on the label, the certificate, or both (International Council for Harmonisation, 2000). A result has a working life.

One set of methods

Each result answers the question its method asks, and nothing wider. In a report on peptide reference standards by scientists at the United States Pharmacopeia (USP) and co-authors, the method described for one peptide, leuprolide acetate, monitored the peptide and its impurities at 220 nanometres by reversed-phase chromatography, and determined main peak content from triplicate injections from a single container (McCarthy et al., 2023).

That figure describes the peptide and the related substances the method can see. Peptide content is a separate question, because counterions, water and residual solvents also occupy mass; the same report accounted for them in its content assignment. Our guides to purity testing and counter-ions cover both figures.

Five Things a Certificate of Analysis Cannot Prove

On its own, a certificate of analysis cannot establish five things, and each is a question the document was never built to answer.

1. Anything about another lot

A certificate for lot A, however clean, says nothing about a vial from lot B, a separate run with its own inputs and its own possible synthesis impurities. The lot number on the document and the lot number on the vial either match or they do not.

2. Identity beyond the methods that were run

A certificate confirms identity only as far as its identity methods can discriminate. Drug specification guidance says identification testing should optimally be able to discriminate between compounds of closely related structure that are likely to be present, that identification by a single chromatographic retention time alone is not regarded as being specific, and that combinations such as HPLC/MS are generally acceptable (International Council for Harmonisation, 1999). That guidance addresses the marketing approval of new drug products and, where applicable, new drug substances; it may be applicable to low molecular weight synthetic peptides and is not sufficient to describe specifications for higher molecular weight ones.

Mass has its own blind spot. The USP report notes that chiral or isobaric amino acids may require additional techniques for full characterization, and it used amino acid analysis to distinguish leucine from isoleucine (McCarthy et al., 2023). Those two residues share the formula C6H13NO2 and the same monoisotopic mass, 131.0946 (PubChem, 2026; PubChem, 2026). A mass result can match the expected value while a closely related structure sits in the vial.

3. Contaminants nobody tested for

Under the manufacturing guidance, a certificate should list each test performed (International Council for Harmonisation, 2000). A contaminant outside that list is not reported, so the document is silent on it.

Bacterial endotoxin, for example, has its own test: FDA guidance says the agency has accepted the Limulus amoebocyte lysate (LAL) test for endotoxins in lieu of the rabbit pyrogen test for more than 30 years (U.S. Food and Drug Administration, 2026). A chromatographic purity figure is a different measurement, and it does not report endotoxin.

A "not detected" entry is a threshold, and it is narrower than absence. It is best read as a result below the method's stated detection or reporting limit. In one standard elemental method, detection limits depend on the sample matrix, the instrumentation and the operating conditions (U.S. Environmental Protection Agency, 1994).

4. What happened after the test

A certificate describes the material at the moment of testing, and shipping and storage come afterwards. ICH stability guidance says the purpose of stability testing is to provide evidence on how the quality of a drug substance or product varies with time under environmental factors such as temperature, humidity and light, and to establish a retest period for a drug substance and recommended storage conditions (International Council for Harmonisation, 2003).

What the material met in transit and on the shelf is recorded elsewhere, if at all, which is why storage and stability belong to the same quality question.

5. That the document itself is genuine

A certificate is a statement made by its issuer, and it cannot verify itself. Under U.S. drug manufacturing rules, a supplier's report of analysis on a drug component may be accepted in place of the manufacturer's own purity, strength and quality testing only if the manufacturer runs at least one specific identity test of its own and validates the supplier's results at appropriate intervals (21 CFR 211.84). Our guide to spotting a fake COA sets out the practical checks.

What Closes Each Gap

Each limit has a matching check, and most start with the lot number.

Recording the lot number beside every result makes the first check routine. Our COA reading guide sets out which fields should match across lots and which legitimately vary.

Drug specification guidance puts the whole idea in one line: "Specifications are an important component of quality assurance, but are not its only component" (International Council for Harmonisation, 1999). A certificate is one strong piece of the quality picture, read best alongside the others.

How Janera Science Publishes Its Certificates

Janera Science lists each posted certificate on the lab results page against a lot number. Where no certificate is posted, the listing reads COA Unavailable. The four tests behind each certificate are set out on our page covering how we test.

Match the lot number on the vial to the one on the certificate, note the date and the tests listed, and ask which of the five gaps your work needs closed. Our guide to what Research Use Only means covers the label itself.

Our guide to verifying peptide purity claims covers the questions to ask before relying on a result.

Frequently Asked Questions

What is a certificate of analysis?

A certificate of analysis is a batch-level record of test results. International API manufacturing guidance says it should name the material, the batch number and the release date, and list each test performed with its acceptance limits and, where numerical, the results obtained (International Council for Harmonisation, 2000).

What is the difference between a certificate of analysis and a certificate of conformance?

A certificate of analysis reports test results for a specific lot. A certificate of conformance is a signed statement that goods meet the stated requirements, and the wording prescribed in a federal procurement clause contains no test results (Federal Acquisition Regulation 52.246-15, 1984). The first can be checked against its own numbers; the second rests on the signer's word unless the buyer inspects the goods.

Does a certificate of analysis apply to every vial in a lot?

By inference, when the lot is homogeneous and the sample was representative. It says nothing about vials from any other lot.

Can a certificate of analysis confirm a peptide's identity?

Only as far as its identity methods reach. Drug guidance does not regard a single chromatographic retention time as specific on its own (International Council for Harmonisation, 1999), and residues of identical mass, such as leucine and isoleucine, can need a further technique such as amino acid analysis (McCarthy et al., 2023).

How do you tell whether a certificate of analysis is legitimate?

A certificate cannot vouch for itself, so confirm the issuing laboratory, its accreditation scope and the report number. Our guide to spotting a fake COA walks through each step.

Does a certificate of analysis mean a material is safe?

No. A certificate reports what named tests found on one lot, and it says nothing about any question those tests did not ask. No certificate makes a research-use-only material suitable for use in humans or animals.

Key Takeaways

A certificate of analysis reports named test results for one lot, measured on a sample, on one date.

On its own, a certificate cannot speak for another lot, confirm identity beyond its methods, cover contaminants nobody tested for, describe the material after testing, or prove its own authenticity.

Each gap has a matching check, and the simplest is matching the lot number on the vial to the certificate.

All Janera Science compounds are supplied strictly for in-vitro laboratory research use only. They are not intended for human or veterinary use, and are not intended to diagnose, treat, cure, or prevent any disease. The statements made on this website have not been evaluated by the U.S. Food and Drug Administration.