Reading a Certificate of Analysis: What Researchers Look For

The Certificate of Analysis is the single most important document in a research peptide transaction. It is the document that translates a vial of white powder into a verified compound with a known purity, identity, and mass — without which any research protocol based on that vial is unreproducible. Yet most researchers buying peptides cannot fully read a Certificate of Analysis, and most suppliers offering one rely on that fact.

This article fixes the asymmetry. We cover what a Certificate of Analysis actually is, the three tests that matter most, the peptide content versus peptide mass distinction that is the single most common source of error, and the red flags that distinguish a credible analytical document from a marketing artifact dressed up to look like one. The Kinetic Compounds lab testing and COA page covers our specific testing methodology; this article covers the general principles.

What a Certificate of Analysis Actually Is

A Certificate of Analysis (COA) is a document that reports the results of analytical tests performed on a specific batch of a specific compound. It is not a generic product specification. It is not a manufacturer’s claim. It is a report from a laboratory documenting what its instruments measured when a sample was tested.

A credible COA has several non-negotiable structural elements:

Batch specificity. The document refers to a specific lot or batch number, not a generic product. Two vials from two different batches of the same compound will have different COAs.

Date of analysis. The testing date is recorded, and the COA cannot be dated before the manufacturing date of the batch it describes.

Laboratory identification. The testing laboratory is named, with sufficient detail to be independently verifiable.

Methodology references. The analytical methods used are identified (HPLC conditions, mass spectrometry configuration, and so on), allowing another laboratory to attempt to replicate the testing.

Analyst signature or authorization. The person or process responsible for releasing the results is recorded.

When any of these elements is missing or generic — for example, a document that lists “Peptide X, 99% purity” with no batch number, no date, and no methodology — the document is not functioning as a Certificate of Analysis. It is functioning as marketing copy that happens to be formatted to look like analytical data [Ref. 1].

The Three Tests That Matter Most

Peptide COAs can include dozens of tests, but three carry most of the analytical weight: HPLC purity, mass spectrometry, and the peptide content determination.

HPLC purity — what it tells you and what it doesn’t

High-performance liquid chromatography (HPLC) separates a sample by passing it through a column packed with material that interacts differently with different molecules. The peptide of interest and any impurities elute from the column at different times, and a detector measures how much of each substance comes through. The result is a chromatogram with peaks at characteristic retention times, and “HPLC purity” is the percentage of the total detector signal accounted for by the main peak [Ref. 2].

In practice, HPLC purity for research peptides typically falls between 95% and 99%. Pharmaceutical-grade peptides are typically 99%+ purity. Anything below 95% should prompt questions; anything claimed at 99.9%+ should also prompt questions, because that level of purity is difficult to achieve and even more difficult to measure reliably.

A critical limitation: HPLC purity reports what fraction of the detectable signal is the main peak, but cannot by itself confirm what the main peak actually is. A peak at the expected retention time could in principle be the labeled compound, a closely related sequence, or in rare cases a different compound entirely that happens to elute at the same time. HPLC purity is necessary but not sufficient.

Mass spectrometry — confirming identity

Mass spectrometry ionizes the sample and measures the mass-to-charge ratio of the resulting ions. The output identifies the molecular weight of the compound in the sample. This is the test that confirms identity: a peak at 4113 Da on a vial labeled Semaglutide confirms the compound matches Semaglutide’s expected molecular weight; a peak at 4814 Da on the same vial would indicate the vial actually contains Tirzepatide; a peak at 3751 Da would indicate liraglutide.

For peptides specifically, mass spectrometry is the single most reliable test for catching mislabeled or counterfeit products [Ref. 3]. The combination of HPLC purity (which says the sample is clean) and mass spectrometry (which says the sample is the right molecule) is what makes a COA analytically credible.

Peptide content — the most misunderstood metric

This is the most consequential metric on a COA, and the one most often misrepresented or omitted entirely.

Lyophilized peptides are never 100% peptide by mass. The dry powder in a vial contains the peptide itself plus counter-ions (typically trifluoroacetate or acetate from the synthesis process), residual water, and trace impurities. Peptide content — sometimes labeled “peptide assay” or “net peptide” — is the percentage of the vial’s mass that is actually the peptide.

A 5 mg vial of BPC-157 with 80% peptide content contains 4 mg of actual peptide and 1 mg of counter-ions and residual moisture. A 5 mg vial of the same compound with 95% peptide content contains 4.75 mg. This is not contamination; it is a normal feature of lyophilized peptide chemistry. But it materially affects dosing calculations in any research protocol designed around mass — if a researcher calculates a dose assuming 5 mg of peptide and the vial actually contains 4 mg, the experimental concentration is 20% below intended.

Reputable suppliers report HPLC purity and peptide content as separate numbers because they measure different things. Suppliers who report only purity, or who collapse the two into a single “purity” claim, are at minimum sloppy and at worst deliberately misleading [Ref. 4].

Red Flags on a Certificate of Analysis

Several patterns recur across questionable COAs.

Generic templates not batch-specific. A COA that does not reference a specific batch number, or that uses identical results across multiple batches, is not analytical documentation. It is a template.

Missing methodology. A credible HPLC report identifies the column, the mobile phase, the gradient, and the detector. A credible MS report identifies the ionization source and mass range. COAs that report results without methodology cannot be independently evaluated.

No analyst signature, no laboratory letterhead. Anonymous COAs are unverifiable by design.

Suspiciously high purity claims. 99.9%+ purity is rare and difficult to measure accurately. Any supplier claiming 99.9%+ across all products has either invested in extraordinary analytical capabilities or is overstating their results.

In-house testing without third-party verification. Manufacturers testing their own products have an inherent conflict of interest. Independent third-party testing exists specifically to remove that conflict.

COA dated before manufacture. A COA must be dated on or after the date the batch was synthesized. COAs dated before manufacture are not analyzing the batch they purport to describe.

Single-test COAs. A COA reporting only HPLC purity, with no mass spectrometry or peptide content data, leaves out the tests that catch the most consequential errors.

Reused COAs across products. If the COA for two different peptides shows identical chromatograms or identical mass spectra, the document is fraudulent on its face.

How Kinetic Compounds Verifies Each Batch

Kinetic Compounds tests every batch of every product through Janoshik Analytical, an independent third-party laboratory. Each COA is batch-specific and reports HPLC purity, mass spectrometry confirmation matching the expected molecular weight for the labeled compound, peptide content as a separate metric from peptide mass, and methodology details sufficient to allow independent replication.

Current COAs are published directly on each product page rather than provided on request. This is a deliberate transparency choice — a COA that has to be requested can be selectively withheld; a COA that is published with the product cannot.

The broader testing approach is documented on our lab testing and COA page, and the analytical standards we work to are documented on our quality standards page. Pharmaceutical specifications for peptide drug substances broadly follow the ICH Q6A guideline [Ref. 6], and reputable research-grade testing applies similar analytical principles.

For specific examples, researchers can review batch reports on our most-requested products: BPC-157, Semaglutide, Tirzepatide, and TB-500. The full research catalog is available through our shop.

Every Kinetic Compounds batch ships with a third-party Certificate of Analysis published directly on the product page. Review our complete testing methodology on the lab testing and COA page, or browse the full research peptide catalog to see current COAs for every product.