How to read a peptide certificate of analysis

A certificate of analysis, or COA, is a document that reports the test results for one batch of a substance. To read one, check five things: that the batch number matches the product in front of you, that each test lists its acceptance limit and an actual number, how identity was confirmed, how purity was measured, and who dated and signed it. A COA reports tests. It does not tell you whether a product is authorized for sale in Canada.

This page walks through each line, using the wording that medicine regulators and international guidelines use for the same document.

What a certificate of analysis is

The international good manufacturing practice guide for active pharmaceutical ingredients, known as ICH Q7, has a section called "Certificates of Analysis". It starts with one batch:

"Authentic Certificates of Analysis should be issued for each batch of intermediate or API on request."

ICH Q7, section 11.40, retrieved 12 October 2026.

The key word is batch. A COA is about one production lot, not about a product name in general. A certificate that carries no batch number, or a batch number that does not match the label, tells you about some other material.

Line 1: name, grade, batch number and date

ICH Q7 lists what should appear at the top of the certificate:

"Information on the name of the intermediate or API including where appropriate its grade, the batch number, and the date of release should be provided on the Certificate of Analysis."

ICH Q7, section 11.41, retrieved 12 October 2026.

Health Canada's good manufacturing practices guide describes a similar document for the raw materials a drug maker buys. Where it sets out what a supplier agreement should specify, it names a certificate of analysis that:

"presents actual numerical results and refers to the batch number, raw material specifications and validated test methods used"

Health Canada, Good manufacturing practices guide for drug products (GUI-0001), section C.02.010, retrieved 12 October 2026.

What to check: the name, the batch or lot number, and a release date. Then compare the batch number with the one printed on the vial or bag.

Line 2: each test, its limit, and the actual result

The body of a COA is a table of tests. ICH Q7 says what each row should carry:

"The Certificate should list each test performed in accordance with compendial or customer requirements, including the acceptance limits, and the numerical results obtained (if test results are numerical)."

ICH Q7, section 11.42, retrieved 12 October 2026.

So every row should give three things: the test, the limit it had to meet, and the number the lab actually got. A row that says only "conforms" or "pass" where a number could be given tells you less than a row with the measured value.

Identity: mass spectrometry

Identity answers one question: is this the peptide named on the label? The European Medicines Agency's guideline on synthetic peptides, which took effect on 1 June 2026, describes the main tool:

"Mass spectrometry (MS) is a powerful analytical tool for the structure elucidation of peptides."

European Medicines Agency, Guideline on the Development and Manufacture of Synthetic Peptides, section 4.3.1, retrieved 12 October 2026.

What to check: whether the identity row names the method, and whether it gives a measured result you can compare with the expected one, rather than a single word.

Purity: HPLC and the related impurities

Purity is usually the headline number. The same guideline explains why it matters:

"Purity is one of the most important critical quality attributes (CQAs) for synthetic peptides."

European Medicines Agency, Guideline on the Development and Manufacture of Synthetic Peptides, section 4.3.2, retrieved 12 October 2026.

For medicines, the guideline also sets the levels at which smaller impurities must be dealt with. It says:

"peptide-related impurities should be reported above 0.1%, identified above 0.5% and qualified above 1.0%"

European Medicines Agency, Guideline on the Development and Manufacture of Synthetic Peptides, section 4.4.1, retrieved 12 October 2026.

In plain words: under this guideline, a medicine's peptide-related impurities are listed once they pass a tenth of a percent, and must be identified once they pass half a percent. When you read a purity figure such as 98%, the remaining 2% is something else. A fuller COA shows the chromatogram or lists the largest impurities, not only the total.

Purity is not content: counter-ions and water

A synthetic peptide powder can contain more than the peptide itself: a counter-ion, which is a salt partner, and some water. The EMA guideline asks for the counter-ion to be named and measured:

"The type of counter ion should be defined, and the amount of counter ions should be controlled"

European Medicines Agency, Guideline on the Development and Manufacture of Synthetic Peptides, section 4.4.1, retrieved 12 October 2026.

It also says how the assay figure is expressed:

"Limits of assays determined by LC are expressed in terms of the counter-ion free, anhydrous substance"

European Medicines Agency, Guideline on the Development and Manufacture of Synthetic Peptides, section 4.4.5, retrieved 12 October 2026.

That means the assay number is calculated as if the salt and the water were taken out. Purity and content are therefore two different numbers. What to check: whether the COA names the counter-ion (for example acetate or trifluoroacetate) and reports water, so the two figures can be read together.

The date, the signature and the maker

ICH Q7 ends its list with who stands behind the document:

"Certificates should be dated and signed by authorised personnel of the quality unit(s) and should show the name, address and telephone number of the original manufacturer."

ICH Q7, section 11.43, retrieved 12 October 2026.

A COA with no date, no signature and no maker's address cannot be traced back to anyone.

Why the numbers need a real test behind them

In Canada, a performance claim made to the public has to rest on testing. The Competition Act says a person engages in reviewable conduct when they make a representation:

"in the form of a statement, warranty or guarantee of the performance, efficacy or length of life of a product that is not based on an adequate and proper test thereof, the proof of which lies on the person making the representation"

Competition Act, s. 74.01(1)(b), retrieved 4 October 2026.

A purity figure on a website is a representation about a product. Whether that section reaches it is a legal question; either way, the COA is where the test behind it should be visible.

What a COA does not tell you

A COA describes what is in one batch. It says nothing about whether a product may be sold in Canada. For that, Health Canada points to a different check:

"Check the label before you buy. Authorized prescription drugs in Canada have an eight-digit Drug Identification Number (DIN). You can also check whether a drug has been authorized for sale by searching Health Canada's Drug Product Database."

Health Canada public advisory, 9 Apr 2026, retrieved 4 October 2026.

A COA laid out in the style of ICH Q7 or the EMA guideline is not proof that the product was made to those standards. Our page on DIN, NPN and how to check a product explains the authorization check, and are peptides legal in Canada? sets out the rules. For the two numbers people mix up most, read peptide content vs purity.

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