certificate of analysis · COA · HPLC · mass spectrometry · peptide purity · peptide research ·Jun 18, 2026

How to Read a Peptide Certificate of Analysis

A Certificate of Analysis (COA) is the document a peptide supplier provides to verify the identity, purity, and quality of a specific lot of material. For laboratories planning research with a peptide reagent, the COA is the primary record of what is in the vial. Yet COAs vary substantially in completeness and rigor, and a research-grade COA from a credible third-party lab looks very different from a single-page in-house document with vague descriptive language. This guide walks through what to look for, what each section means, and the common red flags that distinguish a reliable COA from a marketing document.

What a Complete COA Should Contain

A rigorous peptide COA, suitable for research use, should include at minimum the following sections:

Product identification: peptide name, sequence (one-letter code), CAS number where applicable, and supplier lot number
Batch traceability: manufacture date, certification date, and the testing laboratory name
Appearance: physical description of the material (typically lyophilized white powder)
HPLC purity: reversed-phase HPLC chromatogram with peak integration and a stated purity percentage
Mass spectrometry: mass spec output confirming the expected molecular weight
Endotoxin testing: LAL (limulus amebocyte lysate) assay result, typically reported as endotoxin units per milligram
Counterion content: for trifluoroacetate (TFA) or acetate salts, the residual counterion concentration
Moisture content: typically by Karl Fischer titration
Signatures and lab credentials: the name and signature of the analyst or QC director, and the testing laboratory's contact information

HPLC Purity: The Headline Number

The HPLC purity figure is the number most laboratories cite when comparing peptide quality between suppliers. Reversed-phase HPLC separates the peptide of interest from synthesis byproducts (truncated sequences, deletion peptides, oxidation products) and any residual starting materials. The chromatogram should show a single dominant peak corresponding to the target peptide, with minor peaks contributing the remaining mass.

What to look for:

Stated purity expressed as a percentage with at least one decimal place (e.g., 99.2%)
The chromatogram itself (not just the number), with retention time and peak integration shown
The mobile phase and column described in the methods (typically a water/acetonitrile gradient with 0.1% TFA on a C18 column)
For peer-reviewed research, a purity of ≥98% is the standard threshold

Mass Spectrometry: Confirming Identity

HPLC purity tells you how clean the material is, but it does not tell you what the dominant species is. Mass spectrometry, typically by ESI (electrospray ionization) or MALDI, confirms that the dominant peak corresponds to the expected molecular weight of the target peptide. The mass spec section of a COA should report the observed monoisotopic or average mass and compare it to the theoretical mass calculated from the peptide sequence.

A typical mass spec confirmation is within 1 dalton of the theoretical value for small peptides and within a fraction of a percent for larger peptides. Anything more than that should be questioned.

Endotoxin Testing

For peptides intended for cell culture or in vivo research use, endotoxin contamination can confound experimental results, particularly in immunology, neuroscience, and cardiovascular research where endotoxin-driven inflammation can mask the peptide's actual effect. The LAL assay reports endotoxin in endotoxin units (EU) per milligram of peptide. Research-grade material should report below the laboratory's threshold for the application; for in vivo rodent work, <0.25 EU/mg is a common requirement, though specific thresholds depend on the dose and route.

Batch Traceability

A research-grade COA should be lot-specific: the same supplier may have multiple lots of the same peptide, and the COA must be tied unambiguously to the lot number printed on the vial. Sloppy COAs from low-quality suppliers sometimes report a generic "product-level" COA that does not reference a specific lot, which is essentially a marketing document.

Look for a clearly stated lot number on the COA that matches the vial label, along with manufacture and certification dates. The certification date should be reasonably close to the manufacture date and well within the stated shelf life.

Counterion Content

Synthetic peptides are typically purified by reversed-phase HPLC with trifluoroacetic acid (TFA) in the mobile phase, which leaves residual TFA as a counterion to the basic residues in the peptide. For some research applications, TFA contamination can confound results (TFA has been reported to interfere with cell viability assays at high concentrations). A complete COA reports the residual counterion content; for peptides where TFA is undesirable, suppliers can perform an additional ion-exchange step to convert to an acetate or chloride salt.

Red Flags on a Peptide COA

The COA itself is a document that can reveal quality issues even before you reach the actual numbers. Watch for:

Missing chromatograms: a purity number with no accompanying chromatogram is essentially unverifiable
No mass spec: HPLC purity without mass spec confirmation means you have no proof of identity
No lot number: a generic product COA is not a batch certification
Vague language: phrases like "high purity" or "pharmaceutical grade" without specific numbers
No testing laboratory named: an unsigned, unattributed COA cannot be verified
Implausible purity values: 100.0% purity is not a thing; even the cleanest peptides report 99.5%–99.9%
Same COA across multiple lots: if the supplier's "current COA" does not change when you re-order, the document is decorative rather than analytical

Third-Party vs. In-House Testing

Peptide suppliers fall broadly into two categories on COA practice: those that test in-house and those that send each lot to a third-party analytical laboratory. Third-party testing is the higher standard because it removes the conflict of interest in self-reporting. For laboratories whose research relies on rigorous quality, the third-party route is the standard to look for.

Neo Labs and the Kovera Labs Batch 052026 COA Rollout

Neo Labs publishes the third-party Kovera Labs COA for every batch of every catalog peptide. The current production lot, batch 052026 (certification date 06/15/2026), covers 24 peptides in the catalog including BPC-157, TB-500, NAD+, the GLP receptor agonist family, and the broader nootropic and longevity peptides. Each COA is available on the product page as a downloadable PDF and as a gallery image so the report is visible at a glance. Every COA reports a HPLC purity above 99.2%, the corresponding mass spec verification, and the supporting analytical data.

For background on the specific peptide research literature, see our reviews of BPC-157 research, TB-500 research, NAD+ longevity research, and the GLP receptor agonist research primer.

Research Use Disclaimer

The information above is provided for the qualified researcher selecting a peptide reagent for in vitro and pre-clinical work. Materials supplied by Neo Labs are intended exclusively for qualified laboratory research. They are not for human consumption, clinical use, or veterinary application. Researchers are responsible for compliance with all applicable institutional and regulatory requirements.