Peptide Certificate of Analysis: How to Read, Verify and Interpret CoA Documentation

September 26, 2026 · By My Store 3 Admin

A Certificate of Analysis (CoA) is one of the most important documents in peptide research procurement — and one of the most commonly misunderstood. For researchers sourcing compounds for laboratory use, knowing how to read, verify, and critically assess CoA documentation is a practical necessity. This guide explains what a peptide CoA is, what it contains, how to interpret its key fields, and — critically — what its limitations are.

What is a Certificate of Analysis?

A Certificate of Analysis is a document issued by an analytical laboratory that records the results of testing performed on a specific batch of a compound. It provides evidence that the tested material meets — or in some cases does not meet — a defined specification at the time of analysis.

For research peptides, a CoA typically documents:

The identity of the compound (confirmed by mass spectrometry)
The purity of the compound (measured by HPLC)
The batch or lot number of the material tested
The date on which testing was performed
The laboratory that conducted the analysis

A CoA is not a certificate of safety. It does not establish that a compound is suitable for human administration, that it is free of all possible contaminants, or that it will perform as expected in a specific experimental context. It is an analytical document recording the results of specific tests on a specific sample at a specific point in time.

The Two Core Tests: Identity and Purity

A credible peptide CoA should contain two distinct types of analytical data, which answer different questions:

Identity Testing: Mass Spectrometry

Identity testing answers the question: Is this the compound it claims to be?

The standard method is mass spectrometry (MS), most commonly electrospray ionisation MS (ESI-MS) or MALDI-TOF. The instrument measures the mass-to-charge ratio (m/z) of ionised species in the sample and derives an observed molecular mass. This is compared against the theoretical molecular mass calculated from the target peptide’s amino acid sequence.

If the observed mass matches the theoretical mass within the instrument’s tolerance (typically ±1 Da for ESI-MS), this constitutes identity confirmation — evidence that the correct compound has been synthesised.

Important caveats:

Mass spectrometry confirms molecular mass, not sequence order. Two peptides with the same amino acid composition but different sequence would have identical masses. For research purposes, this is generally acceptable because SPPS synthesis of a defined sequence is highly sequence-specific, but it is a theoretical limitation.
MS identifies the dominant species in the sample. The presence of impurities at lower concentrations may not be resolved unless specifically sought.

Purity Testing: HPLC

Purity testing answers the question: What proportion of the sample is the target compound?

High-performance liquid chromatography (HPLC) separates the components of a dissolved sample by passing it through a column under high pressure. Each component travels through the column at a different rate and is detected as it elutes, producing a chromatogram — a graph of detector signal over time.

Purity is reported as the percentage of the total peak area attributable to the target compound. A purity of ≥98% means the target peptide accounts for at least 98% of the detected signal, with all impurities — deletion sequences, oxidation products, residual reagents — collectively representing no more than 2%.

Research-grade peptides are generally expected to meet ≥98% purity by HPLC. Lower purity grades exist but carry greater uncertainty about the nature and concentration of impurities.

Key terms to understand when reviewing HPLC data:

Peak area percentage — the proportion of the total detected signal attributable to the target compound. This is the primary purity metric.
Retention time — the time taken for the target compound to elute from the column. Consistent retention times across batches indicate a consistent compound.
Baseline resolution — the degree to which peaks are separated. Well-resolved peaks indicate a clean sample; overlapping peaks may indicate co-eluting impurities.

Understanding Every Field on a Peptide CoA

Product Name and CAS Number

The product name and CAS (Chemical Abstracts Service) registry number uniquely identify the compound. Verify that these match the compound you ordered. CAS numbers are compound-specific: for example, BPC-157 has the CAS number 137525-51-0. A CoA bearing a different CAS number does not document the compound you intended to purchase.

Batch or Lot Number

The batch number is the single most important traceability field on a CoA. It links the analytical document to a specific production run of the compound. If you receive material from Batch A, a CoA for Batch B — however high its stated purity — does not document the material you have received.

Always verify that the batch number on the CoA matches the batch number on the product label or packaging. Suppliers who cannot provide batch-matched documentation are not providing meaningful quality assurance.

Testing Date

The testing date records when the analysis was performed. Peptide purity is not static: compounds degrade over time, particularly if stored incorrectly. A CoA with a testing date of several years ago may not reflect the current condition of the material.

When evaluating CoA documentation, consider the time elapsed since testing and whether the storage conditions during that period were appropriate to maintain compound integrity.

HPLC Purity (%)

The purity figure, expressed as a percentage by peak area. For research-grade material, this should be ≥98%. Some CoAs report purity to one decimal place (e.g. 98.7%); others report a range or minimum. Confirm this figure relates to the specific batch number documented.

Observed Molecular Mass vs Theoretical Molecular Mass

From mass spectrometry data. The observed mass should match the theoretical mass of the target peptide sequence within instrument tolerance. A significant discrepancy indicates either an error in synthesis, a measurement artefact, or that the compound is not what it claims to be.

Appearance

A physical description of the material, typically “white to off-white lyophilised powder” for research peptides. This is a basic visual quality check and is not a substitute for analytical testing.

Testing Laboratory

The name and, where available, accreditation status of the laboratory that conducted the analysis. This field is critical for evaluating the independence and credibility of the documentation.

Third-Party vs In-House Testing: Why It Matters

A CoA produced by the manufacturer’s own in-house laboratory and a CoA produced by an independent third-party analytical laboratory are not equivalent in terms of the assurance they provide.

In-house testing is subject to potential conflicts of interest: the laboratory producing the result has a commercial interest in the outcome. This does not mean in-house CoAs are fraudulent, but it does mean they carry a lower level of independent verification than third-party documentation.

Third-party testing, conducted by an accredited analytical laboratory with no commercial relationship to the manufacturer, provides a higher level of assurance for precisely this reason. Researchers conducting publication-quality work should seek suppliers whose CoA documentation is produced by independent third parties.

All Bloom Vitality research peptides are tested by independent third-party laboratories. Batch-specific documentation is available via our Certificates & Documentation page.

How to Verify CoA Documentation

Receiving a CoA is not the same as verifying it. Steps researchers can take to assess CoA credibility:

Check batch number correspondence — confirm the CoA batch number matches the label on the material received
Confirm the compound identity — verify the product name, CAS number, and molecular weight against independent reference sources
Assess the testing laboratory — look up the named laboratory independently; accredited laboratories are registered with bodies such as UKAS (UK Accreditation Service) or equivalent national accreditation bodies
Check the testing date — consider whether sufficient time has elapsed since testing to raise concerns about compound stability
Assess the data format — a credible CoA includes actual chromatogram data or mass spectrum output, not just a summary table. Raw or supporting data should be available on request from a reputable supplier.

Janoshik Verification

Some suppliers use Janoshik Analytical, an independent third-party testing laboratory that specialises in research compound analysis. Janoshik CoAs include a unique order reference that allows independent online verification at verify.janoshik.com. This allows researchers to confirm that the CoA document provided matches the result held on the laboratory’s own records — an additional layer of authenticity assurance beyond simply receiving a PDF.

Bloom Vitality uses Janoshik Analytical for independent batch testing. For a full guide to reading and verifying a Janoshik CoA, see: What is a Janoshik CoA and How Do You Verify One?

CoA Red Flags

When reviewing CoA documentation from any supplier, treat the following as significant warning signs:

No identifiable laboratory — a CoA without a named, contactable testing laboratory cannot be independently assessed or verified
No batch or lot number — without a batch number, there is no way to confirm the CoA relates to the material actually supplied
Purity reported without a testing method — a purity figure is meaningless without specifying the analytical method (e.g. HPLC by peak area %); any supplier can state any number without methodological grounding
In-house testing only — documentation produced solely by the manufacturer’s own laboratory carries inherent conflict of interest and provides weaker assurance than independent third-party testing
No identity confirmation — purity data alone (HPLC) does not confirm the compound is what it claims to be; mass spectrometry identity confirmation should be present
Missing or very old test date — an undated CoA, or one with a test date significantly predating the supply, does not document the current condition of the material

What a CoA Cannot Tell You

Understanding the limitations of CoA documentation is as important as understanding what it confirms. A peptide CoA does not establish:

Safety for human use — analytical purity does not imply suitability for human administration. Research-grade peptides are not manufactured to pharmaceutical GMP standards and are not approved medicines.
Absence of all contaminants — standard HPLC and MS testing does not screen for all possible contaminants, including heavy metals, endotoxins, or residual synthesis reagents unless specifically tested and documented.
Biological activity — chemical identity and purity do not confirm that a compound will behave as expected in a biological system. Biological activity assays are separate from analytical quality testing.
Stability over time — a CoA reflects compound condition at the time of testing. Subsequent handling, storage conditions, and time elapsed all affect actual compound integrity at the point of experimental use.
Equivalence across batches — a CoA is batch-specific. Researchers should obtain updated CoA documentation for each new batch sourced, even from the same supplier.

Endotoxin and Sterility Testing

Standard peptide CoAs document chemical identity and purity. For researchers with specific requirements around endotoxin levels (lipopolysaccharide contamination from gram-negative bacteria) — particularly relevant for cell culture work where endotoxin can confound results — additional testing is required. Endotoxin testing (typically by LAL assay) and sterility testing are separate analyses that may be available from specialist suppliers on request but are not universally included in standard research peptide CoAs.

Bloom Vitality CoA Documentation

Batch-specific Certificates of Analysis for all Bloom Vitality research compounds are available via our Certificates & Documentation page. All testing is conducted by independent third-party analytical laboratories. Our approach to quality assurance is described in full on the Testing & Quality page.