Don’t Start With the 99%: How to Read a COA

Don’t begin with the biggest percentage on the page.

A Certificate of Analysis, or COA, summarizes analytical information associated with a sample, batch or material.

Because formats differ between laboratories and organizations, there is no single universal visual template.

But there is a much better way to approach one than simply searching for a purity number.

1. Identify the material

Start at the top. What material does the report claim to describe?

Look for information such as the material or sample name and other identifying information provided by the laboratory.

2. Find the sample or lot identifier

Next ask: Which physical sample does this report correspond to?

Look for lot numbers, batch identifiers, sample IDs or laboratory accession identifiers where applicable.

Without a meaningful connection between the tested sample and the material being represented, even authentic analytical data can be difficult to contextualize.

3. Identify the laboratory

Who performed the analysis?

Look for the testing organization’s identity and whatever report-verification information it provides.

This becomes particularly important when analytical reports are redistributed by third parties.

4. Read the analytical method

Before interpreting the result, determine how the result was generated.

Was the sample evaluated using chromatography? Mass spectrometry? A microbiological method? An endotoxin assay? Something else?

The method tells you what kind of analytical question the result may be capable of addressing.

5. Read the result

Only now should the headline result become the focus.

A reported value is meaningful only when connected to:

sample → method → measurement → interpretation.

A number without that context can easily be misunderstood.

6. Look for specifications and units

A result such as 0.42 means very little without knowing what was measured and in what units.

Similarly, “Pass” should ideally be understood in relation to a stated specification or criterion.

7. Ask what was NOT tested

This is one of the most useful habits in analytical literacy.

Suppose a COA contains: HPLC purity: 99.1%

Do not silently add: identity confirmed, sterility confirmed, endotoxin tested, quantity confirmed — unless appropriate supporting analysis is actually present.

A simple COA reading framework

Whenever you encounter an analytical report, work through:

WHAT → WHICH SAMPLE → WHO TESTED IT → HOW → RESULT → SPECIFICATION → LIMITATIONS

That sequence is far more informative than jumping immediately to the largest number on the document.