How to Read a Peptide Certificate of Analysis (COA) - HPLC Purity Explained

If a compound is going into you, the Certificate of Analysis (CoA) is not supplementary documentation - it is the primary evidence of what you have actually been given. A CoA is the formal record of the analytical testing performed on a specific batch of a compound. It tells you what purity the compound was found to have, how that purity was measured, which laboratory performed the analysis, and which specific production batch the results apply to. Without a meaningful CoA, a researcher has no objective basis for trusting the quality of a compound, and no foundation for comparing results to published literature that relied on defined purity standards.

Despite this, CoA documents are widely misunderstood - and some suppliers issue documentation that uses CoA formatting while containing very little useful information. This guide explains what a legitimate CoA should contain, how HPLC purity analysis works and what the numbers mean, how to read a chromatogram, what purity thresholds to look for in a research context, and how to distinguish independent from in-house testing. Where relevant, we link to the publicly available lab results for Baseline's research compounds so you can see what a well-documented CoA looks like in practice.

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A Certificate of Analysis is a formal document issued by an analytical laboratory confirming the results of testing performed on a specific batch of a substance. In the context of research peptides, a CoA should provide objective evidence of: the compound's identity (that it is the molecule it is labelled as), the compound's purity (what percentage of the measured sample is the target peptide as opposed to impurities), and the specific batch to which the results apply.

CoA documents in the research peptide industry vary significantly in quality and information content. Some are produced by independent third-party laboratories with established reputations and verifiable results. Others are produced in-house by the supplier themselves. Some include full analytical data including chromatogram outputs and mass spectra. Others provide only a summary figure. Understanding the difference between these formats is essential for evaluating what a CoA actually tells you.

High-performance liquid chromatography (HPLC) is the standard analytical method used to measure peptide purity. Understanding the basic principle of how HPLC works helps in interpreting what the purity figure on a CoA actually represents.

The principle of chromatographic separation

HPLC works by separating the components of a sample as they pass through a column packed with a stationary phase material. A mobile phase - a liquid solvent system - carries the sample through the column. Different molecules in the sample interact differently with the stationary phase, causing them to travel through the column at different rates. Each component emerges (elutes) from the column at a different time, known as its retention time.

As components elute, a detector - typically a UV/Vis spectrophotometer in peptide analysis - measures their absorbance. This produces a chromatogram: a graph plotting detector signal (absorbance) on the Y axis against time on the X axis. Each component in the sample appears as a peak in the chromatogram at its characteristic retention time.

From chromatogram to purity percentage

The area under each peak in the chromatogram is proportional to the amount of that component in the sample. By summing all peak areas and calculating each individual peak's area as a percentage of the total, the laboratory can determine what proportion of the detected material is the target peptide versus other substances (impurities, degradation products, residual synthesis byproducts).

The purity figure reported on a CoA - for example, 98.3% - means that 98.3% of the UV-detected material in the sample eluted at the retention time characteristic of the target peptide. The remaining 1.7% represents other detected species. This is referred to as area percentage purity, and it is the standard reporting format for research peptide CoA documents.

What to look for in a chromatogram

When a CoA includes the actual chromatogram output (rather than just a summary purity figure), you can assess the result more directly. In a high-purity sample, you should see a dominant, well-defined single peak - tall, sharp, and symmetrical - at the characteristic retention time of the target compound, with minimal other peaks. Small additional peaks to the left or right of the main peak represent impurities. If the chromatogram shows multiple prominent peaks of comparable height, or a wide, irregularly shaped main peak with significant shoulders, this indicates a lower purity or a more complex mixture.

Not all CoA documents include the chromatogram image itself - some include only the calculated area percentage summary table. Both formats are valid, but a CoA that includes the full chromatogram output provides more transparency. Janoshik Analytical CoA documents, for example, include both the numerical purity data and the chromatogram output, enabling direct visual review of the analysis.

HPLC measures purity but does not definitively confirm molecular identity. A sample could in principle be very pure - consisting mostly of a single compound - while that compound is not the target peptide. This is where mass spectrometry (MS) plays a complementary role.

Mass spectrometry measures the mass-to-charge ratio of ionised molecules in a sample. For peptides, this allows the molecular weight of the compound present in the sample to be directly measured. If the measured molecular weight matches the theoretical molecular weight of the stated compound, this provides strong evidence that the sample contains what it is labelled as - not merely that it is a pure single substance.

A comprehensive CoA for a research peptide should include both HPLC purity data and mass spectrometry confirmation. Purity without identity confirmation leaves a gap in the quality evidence. The two methods together provide a robust quality assurance basis: the compound is what it claims to be (MS confirmation) and it is present at high purity (HPLC area percentage).

Research peptide CoA documents commonly report purity figures ranging from around 95% at the lower end to 99%+ at the higher end. Understanding what these thresholds mean in practice is important for evaluating supplier quality and for interpreting research results in the context of published literature.

98% and above: research grade standard

A purity of 98% or above is generally considered research grade for peptide compounds. At this level, the overwhelming majority of the measured material is the target compound, and the impurity fraction is small enough that it is unlikely to significantly confound experimental results in most research contexts. Many published pre-clinical studies use compounds in this purity range.

95-98%: acceptable but lower quality

Purity figures in the 95-98% range are commonly encountered and may be acceptable for some research applications, but they represent a meaningfully higher impurity fraction than 98%+ compounds. If a researcher is working with a compound at 95% purity and comparing results to published literature that used 99% purity material, the impurity difference could be a relevant variable. For research applications where compound quality matters to result interpretation, the higher purity range is preferable.

Below 95%: not good enough

Anything below 95% should not be going into a person. At this level, one in twenty or more molecules in the sample is not the target compound — a significant and unpredictable variable, and an unnecessary one. Anything offered at sub-95% purity is not meeting the standard you should expect.

Baseline's compounds are verified by Janoshik Analytical. Lab results for current batches can be reviewed before purchase for the BPC-157/TB-500 blend, Retatrutide, GHK-Cu, and CJC-1295/Ipamorelin.

A batch number (also called a lot number) on a CoA is not an administrative detail - it is the critical link between the document and the specific production run it applies to. Without a batch number, a CoA cannot be meaningfully connected to the compound you have received. A supplier could theoretically produce one excellent batch, generate a CoA for it, and then supply later batches of lower quality while presenting the same CoA document. Batch numbers prevent this: if you have a batch number on your compound and a CoA with the same batch number, you can verify that the CoA applies to what you received.

For research recordkeeping, batch numbers also enable traceability between experiments. If two studies produce different results, and those studies used compounds from different batches, the batch numbers allow researchers to investigate whether compound quality was a variable. This kind of traceability is important for scientific rigour and reproducibility.

When evaluating a supplier's CoA, confirm: is a batch or lot number clearly stated? Does the batch number on the CoA match what is on the vial or packaging you receive? If these numbers are absent or do not correspond, the documentation is not serving its function.

Perhaps the single most important question to ask about any peptide CoA is: who conducted the analysis? The answer determines how much confidence you can place in the results.

In-house testing

In-house testing means the supplier has performed the HPLC and mass spectrometry analysis themselves, using their own equipment and personnel. This is not inherently unreliable - many suppliers have competent internal analytical capabilities. However, it introduces a fundamental conflict of interest: the entity that produced the compound is also the entity certifying its quality. There is no external check on whether the equipment was calibrated correctly, whether the analysis was performed as described, or whether the results as reported accurately reflect what was measured. In-house CoA documents cannot be independently verified.

Third-party independent testing

Independent third-party testing means the analysis was performed by a separate laboratory with no commercial relationship to the product being tested. The testing laboratory has no incentive to report a favourable result - they simply analyse what they receive and report what they find. This removes the conflict of interest and provides an objective quality check.

The most credible suppliers in the research peptide market use independent third-party laboratories for their CoA documentation. Janoshik Analytical has established itself as one of the most widely recognised and trusted testing laboratories in the research peptide sector internationally. Janoshik CoA documents include a verification code that allows anyone to check the document's authenticity directly through Janoshik's own portal - this is a further level of assurance compared to third-party documents that cannot be independently verified.

Baseline uses Janoshik Analytical for all CoA testing. This means every purity claim is verifiable, not merely stated. Researchers can review lab results for specific compounds, including for the BPC-157/TB-500 blend, before ordering from the Baseline catalogue.

When you receive a CoA document for a research peptide, the following checklist covers the key elements to review.

• Laboratory name: Is the issuing laboratory clearly identified? Is it an independent third-party laboratory or the supplier's own internal team?
• Compound name and molecular formula: Does the document clearly state the compound name? Is the molecular formula or CAS number included?
• Batch or lot number: Is a specific batch number stated? Does it match the batch number on the product you received?
• Testing date: When was the analysis performed? Is it recent enough to be relevant to the batch you have received?
• HPLC purity percentage: Is a purity figure stated as an area percentage? Is the purity at or above 98%?
• Chromatogram output: Is the actual chromatogram graph included, or only a summary table? If included, does the chromatogram show a dominant single peak consistent with high purity?
• Mass spectrometry data: Is MS data included to confirm molecular identity alongside HPLC purity?
• Verification: Can the document be independently verified (for example, via a Janoshik verification code)?

A CoA that passes all these checks provides a strong quality evidence basis for the batch in question. Missing elements - particularly the absence of independent testing, batch numbers, or mass spectrometry identity confirmation - represent gaps in the quality case for the compound.

Every batch is Janoshik-verified and your consultant can show you the report for yours, letting you review the analytical data before ordering. This is a level of pre-purchase transparency that is not universal in the research peptide market. The following lab results pages are available for direct review:

• BPC-157 / TB-500 Lab Results - Janoshik-verified CoA for the dual tissue repair peptide blend
• Retatrutide Lab Results - Janoshik-verified CoA for the GLP-1/GIP/glucagon triple agonist
• GHK-Cu Lab Results - Janoshik-verified CoA for the copper peptide compound
• CJC-1295 / Ipamorelin Lab Results - Janoshik-verified CoA for the growth hormone secretagogue blend

Reviewing these documents allows researchers to assess purity percentages, confirm molecular identity data, and verify that the documentation meets the standards described in this guide before placing an order. All products in the Baseline catalogue, including the CJC-1295/Ipamorelin research pen, carry full CoA documentation for the specific batch.

Nothing here is a treatment plan. They are not intended for human or animal consumption, are not approved therapeutic agents in any jurisdiction, and are not sold for diagnostic or medicinal purposes. This article is for informational purposes only and does not constitute medical advice.