How to Read a Peptide Certificate of Analysis (COA)

A Certificate of Analysis, commonly abbreviated to COA, is a document used to communicate analytical information about a material or sample.

For research peptides, a COA may contain information such as the identity of the submitted sample, analytical methods used, chromatographic results, mass-spectrometric information and reported analytical values.

But not every COA contains the same information, and the presence of a certificate does not automatically mean that every characteristic of a material has been established.

Reading a COA properly means looking beyond a single percentage and understanding what was analysed, how it was analysed and what the reported results actually demonstrate.

What is a Certificate of Analysis?

At its simplest, a Certificate of Analysis is a document reporting analytical information associated with a particular material or sample.

The exact format varies between laboratories and organisations.

Depending on the analysis performed, a peptide-related report might contain:

• sample or reference information
• laboratory information
• date of analysis
• analytical methods
• chromatographic results
• chromatograms
• mass-spectrometric results
• spectra
• reported purity or other analytical values

A COA should therefore be read as a collection of analytical information rather than simply as a certificate containing a purity number.

Step 1: Identify who issued the report

Start by looking at the laboratory or organisation named on the report.

This helps establish the source of the analytical information.

Where available, look for details such as:

• laboratory name
• report or certificate number
• contact information
• date of issue or analysis
• analytical methods performed

It is also useful to distinguish between the organisation that performed the analysis and the organisation that supplied or submitted the sample.

These are not necessarily the same entity.

A report commissioned by a supplier, for example, is not automatically the same thing as a report independently commissioned by a retailer or another organisation further along the supply chain.

Step 2: Check what sample the report refers to

An analytical result only has meaning in relation to the sample that was actually analysed.

Look for identifying information such as:

• compound or sample name
• sample reference
• laboratory reference
• lot or batch identifier, where applicable
• client or submitting organisation
• analysis date

Not every report will contain every one of these fields.

The important question is whether the document provides enough information to understand what material the analytical result relates to.

A COA for one submitted sample should not automatically be assumed to describe every sample or every unit of material with the same compound name.

Step 3: Identify which analytical methods were used

Next, look at how the sample was analysed.

For research peptides, two commonly encountered analytical techniques are:

High-Performance Liquid Chromatography (HPLC)

and

Mass Spectrometry (MS).

These techniques provide different kinds of information.

HPLC is primarily a chromatographic separation technique.

Mass spectrometry provides information based on the mass-to-charge characteristics of ions generated from the analysed material.

The two can also be combined as LC-MS, where liquid chromatography separates components before mass-spectrometric detection.

Knowing which method produced a result is essential to interpreting what that result means.

Step 4: Read the HPLC result carefully

A peptide COA may contain a reported chromatographic purity value such as:

HPLC Purity: 99.1%

This number should be interpreted in the context of the chromatographic method.

In simplified terms, a chromatographic purity percentage commonly describes the relative peak area attributed to the principal detected component compared with other relevant detected peaks under the analytical conditions used.

It does not automatically mean that 99.1% of everything physically contained in a vial has been proven to be the target peptide.

Chromatographic purity, molecular identity and absolute quantity are separate analytical concepts.

For a deeper explanation of HPLC, see our Research Library guide: “What Is HPLC? Understanding Peptide Purity Analysis.”

Step 5: Look at the chromatogram

If the report includes an HPLC chromatogram, examine it alongside the reported purity figure.

A chromatogram shows detector response as components emerge from the chromatographic system.

These responses appear as peaks.

A principal peak may represent the dominant chromatographic component, while smaller peaks can represent additional detectable components.

The area associated with chromatographic peaks can be used in calculating relative chromatographic composition.

However, chromatographic separation is important.

If components are not adequately separated, more than one component can potentially contribute to what appears as an unresolved chromatographic peak.

This is one reason the chromatogram and analytical method provide useful context beyond the final percentage alone.

Step 6: Look for identity information

Purity and identity answer different questions.

A high chromatographic purity result tells you about the relative chromatographic composition detected by that method.

It does not, by itself, necessarily establish what the principal component is.

Mass spectrometry can provide complementary evidence supporting molecular identity.

For synthetic peptides, the expected molecular characteristics are known from their chemical composition.

Mass-spectrometric analysis can therefore compare observed mass-related information with what would be expected for the target material.

If a report contains both chromatographic and mass-spectrometric information, the two forms of evidence should be considered separately and together.

For a fuller explanation of this distinction, see: “Peptide Purity vs Identity: What’s the Difference?”

Step 7: Understand what a mass spectrum contributes

A mass spectrum is different from an HPLC chromatogram.

Rather than displaying chromatographic detector response over retention time, mass spectrometry examines ions according to their mass-to-charge ratio.

Synthetic peptide characterisation commonly uses techniques including LC-MS and MALDI-TOF mass spectrometry.

Observed mass-related information can be compared with the expected molecular characteristics of the target peptide.

This can provide evidence supporting identity.

More advanced mass-spectrometric techniques can also be used in peptide impurity characterisation.

The presence of mass-spectrometric data can therefore add a different layer of analytical information from chromatographic purity alone.

Step 8: Check the analytical date

Analytical reports should be associated with a date.

This may be:

• the sample receipt date
• analysis date
• report date
• certificate issue date

depending on the laboratory.

Dates help place the analytical result in context and distinguish one analysis from another.

They are particularly useful when multiple reports exist for the same compound or when analytical testing is performed at different times.

Step 9: Don’t treat the highest percentage as the whole report

It is tempting to open a COA, find “99%+” and stop reading.

That misses most of the useful information.

Instead, consider:

• What sample was analysed?
• Who performed the analysis?
• When was it analysed?
• Which analytical technique generated the percentage?
• Is the chromatogram shown?
• Is molecular identity information available?
• Is mass-spectrometric data included?
• Does the report identify the analytical method?
• Is the reported result being interpreted within the limits of that method?

A COA becomes considerably more informative when these questions are considered together.

What doesn’t a COA automatically prove?

A COA should not be treated as evidence for claims that the underlying analytical work did not establish.

For example, an HPLC chromatographic purity result does not automatically establish:

• absolute vial quantity
• molecular identity on its own
• the composition of material that was not represented or detected by that particular method
• the characteristics of unrelated samples
• the analytical status of every future unit sold under the same product name

The scope of a report should remain tied to the sample and methods actually represented by that report.

Supplier documentation vs independently commissioned analysis

Another useful distinction is who commissioned the analytical work.

A supplier may provide analytical documentation associated with material in its supply chain.

Separately, another organisation may choose to commission its own analysis from a laboratory.

Both may provide useful information, but they should not be presented as though they are the same thing.

If a report was commissioned by a supplier, it should not be described as independently commissioned by another company.

Clear attribution helps preserve the meaning of the analytical record.

How Lumina approaches analytical reports

At Lumina Biologics, scientific product information and analytical reports are treated separately.

General information such as a compound's molecular formula, molecular weight or peptide sequence describes characteristics of the compound itself.

An analytical report relates to the particular sample that was submitted for analysis.

Where Lumina commissions independent analytical testing and approves the resulting report for publication, the corresponding analytical information may be displayed with the relevant research compound.

Where no approved Lumina analytical report exists, we do not substitute an assumed purity percentage or present supplier documentation as though it were Lumina-commissioned analysis.

This approach allows analytical claims to remain tied to the evidence that supports them.

A quick COA reading checklist

When reading a peptide Certificate of Analysis, check:

1. Who issued the report?
2. What sample was analysed?
3. Is there a sample, laboratory or other reference identifier?
4. When was the analysis performed?
5. Which analytical methods were used?
6. Is an HPLC chromatogram included?
7. What exactly does the reported purity figure represent?
8. Is mass-spectrometric or other identity information provided?
9. Are the analytical method and supporting data available?
10. Are the conclusions limited to what the analysis actually demonstrates?

If those questions can be answered, the COA becomes much easier to interpret meaningfully.

The key takeaway

A Certificate of Analysis is more than a purity percentage.

The most useful reports provide context about:

• the sample
• the laboratory
• the analytical method
• chromatographic results
• identity information
• supporting analytical data

HPLC, mass spectrometry and other analytical techniques answer different questions.

Reading those results together provides a much clearer picture than treating one number as a complete description of a research material.

The goal is not to find the largest percentage.

It is to understand what was measured, how it was measured and what the evidence actually supports.