How to Read a Certificate of Analysis

What each section of a COA reports, including identity, purity and method, and how to match the report to the lot number on your vial.

A Certificate of Analysis (COA) is the document that records what a laboratory tested in one specific lot of material, and what it found. Reading one well takes a few minutes and tells you far more than a product page can. This guide walks through each part of a typical peptide COA, what it means, and what to check against the vial in your hand.

1. What a COA is, and is not

A COA is a report about a lot, meaning one production run of material made and tested together. It records the tests performed, the methods used and the results. It is evidence of what was measured. It is not a certificate of approval, and it does not establish that a material is safe, effective or suitable for any purpose other than the laboratory research it is supplied for.

Two rules make a COA useful: it must be for the same lot as your vial, and it must state which methods produced each result. A report that is missing either is much harder to rely on.

2. Step one: match the lot number

Before reading any results, confirm the report belongs to your material.

Find the lot number on the label of your vial.
Find the lot number on the COA. It is usually near the top, next to the product name.
Check they are identical, character for character.
Check the compound name and the stated amount per vial match the label.

If any of these do not match, do not rely on the report. Contact the supplier with your order number and the lot number from the vial.

3. The parts of a COA

Layouts differ between laboratories, but most peptide COAs contain the same building blocks.

Section	What it tells you	What to check
Header	Product name, lot number, report date, testing laboratory, sample received date	Lot number matches your vial; the report date is after the sample date; the laboratory is named
Appearance	Physical description of the material, such as “white lyophilised powder”	Matches what you received in the sealed vial
Identity	Whether the molecule is the intended one, usually by mass spectrometry	Observed mass is close to the expected (theoretical) mass, and the method is stated
Purity	The share of the sample that is the target peptide, usually by HPLC	The purity value, the detection wavelength, the column and gradient or method reference
Quantity	Stated net content per vial, if tested	Whether it is a measured result or only the label amount
Additional tests	Anything else reported, such as water content, residual solvents, endotoxin or sterility	Only what is listed. Do not assume a test was run if it is not shown
Sign-off	Analyst or reviewer name, signature or authorisation, and a date	The report has been reviewed and is dated

4. Identity: mass spectrometry

Identity answers the question is this the molecule it is labelled as? Mass spectrometry (MS) measures the mass of the molecules in a sample. Each peptide has an expected mass calculated from its amino-acid sequence. On a COA you will usually see two numbers: the theoretical mass and the observed mass.

The two should agree closely. Small differences are normal and depend on the instrument.
Peptides often appear at several charge states, so a spectrum may show multiple peaks that all point back to the same mass.
A matching mass supports identity. It does not, on its own, measure purity.

5. Purity: HPLC

Purity answers a different question: how much of the sample is the target peptide? High-performance liquid chromatography (HPLC) separates the components of a sample and shows them as peaks on a chromatogram. The purity figure is usually calculated from the area of the main peak as a share of the total area of all peaks.

One dominant peak with small side peaks is what a high-purity result looks like.
Method details matter. A purity value means more when the report states the column, the mobile phase or gradient, and the detection wavelength.
Area percent is not the same as content. It shows the share of detected material, not how many milligrams are in the vial.
Look at the chromatogram itself, not only the number. The peak shapes and the baseline tell you a lot.

Why both methods? HPLC and mass spectrometry answer different questions. HPLC tells you how much of the sample is one compound; MS tells you what that compound is. A report that has only one of them tells you only half the story, and neither should be assumed to have been run for every lot. Check what your COA lists.

6. Things to look for

Signs of a more reliable report

The lot number matches your vial exactly.
The testing laboratory is named and independent of the manufacturer.
Methods are stated for each result.
Raw data, such as the chromatogram and mass spectrum, are shown and not only summarised.
The report is dated and signed or authorised.

Signs to ask questions

No lot number, or a lot number that does not match the label.
A single result with no method (for example, “99% pure” and nothing else).
No laboratory name or contact details.
Identical results for many different lots or products.
Images that look edited, cropped or low-resolution in a way that hides detail.
A report that has been changed since it was issued, with no revision noted.

7. What a COA cannot tell you

A COA is a snapshot of one lot at the time of testing. On its own it cannot tell you how the material has been stored since, whether a sealed vial has been mishandled in transit, or whether the material is suitable for any particular experiment. It does not show approval by any regulatory body. Trinity Research materials are supplied for laboratory research use only, and nothing in a COA changes that.

If something on your report does not look right, contact us before you use the material. Include your order number and the lot number from the vial, and we will look into it under our Refunds & Returns policy.