A Certificate of Analysis, or CoA, is the single most important document a research peptide supplier can give you. It is the independent evidence that the compound in the vial is what the label says it is — at the purity claimed, and free from contaminants. Yet most CoAs are dense with technical terms that are rarely explained. This guide breaks down exactly what each section means, so you can evaluate any supplier's CoA with confidence.
## What a Certificate of Analysis actually is
A CoA is a batch-specific report produced when a peptide is tested by an analytical laboratory. "Batch-specific" is the key phrase: a genuine CoA corresponds to one particular production run of one particular compound, and it carries a batch or lot number that should match the number printed on your vial. A generic CoA that is reused across every batch tells you nothing about the vial in your hand.
At Peptide Pal, every batch is tested by accredited third-party laboratories, and the CoA for each compound is available on its product page.
## The key sections, explained
### 1. Identity — is it the right compound?
The top of a CoA states the peptide name, its molecular formula, and its theoretical molecular weight. This confirms which compound was tested. The molecular weight matters because it is later cross-checked against the mass spectrometry result to prove the molecule is structurally correct.
### 2. HPLC purity — how pure is it?
HPLC (High-Performance Liquid Chromatography) is the test behind the "99%+ purity" figure you see quoted. It separates the sample into its component parts and measures each as a percentage of the whole. A purity of 99% means that 99% of the material is the target peptide and only 1% is minor impurities from the synthesis process.
On the CoA this appears as a chromatogram — a graph with a large, sharp main peak (your peptide) and ideally very few small peaks around it. The purity percentage is calculated from the area under that main peak. As a rule of thumb for research compounds, look for 98% or higher.
### 3. Mass spectrometry — is the structure correct?
HPLC tells you how pure the sample is; mass spectrometry (MS) tells you whether the pure part is actually the correct molecule. The MS result reports the measured molecular weight, which should match the theoretical molecular weight from the identity section, usually within a fraction of a percent. A match confirms the peptide was synthesised correctly. A mismatch is a red flag, even if HPLC purity looks high.
### 4. Net peptide content
This is one many researchers overlook. A lyophilised peptide vial also contains residual water and counter-ions from synthesis, so the actual mass of peptide can be lower than the total powder weight. Net peptide content (sometimes "peptide content by nitrogen analysis") tells you what proportion of the powder is genuinely peptide — important for accurate reconstitution calculations.
### 5. Appearance and physical tests
Most CoAs note the expected physical appearance (typically a white to off-white lyophilised powder) and may include water content or endotoxin results. These are supporting checks on overall quality and handling.
## How to tell a genuine CoA from a fake
Unfortunately, CoAs can be forged. Here is how to protect yourself:
- **Check the batch number matches your vial.** This is the most important test. No match, no confidence.
- **Look for an independent laboratory.** A CoA from a named, accredited third-party lab carries far more weight than one produced in-house by the seller.
- **Cross-check the numbers.** The MS measured weight should match the theoretical weight. If a supplier lists a molecular weight that does not match the named peptide, something is wrong.
- **Be sceptical of "100% purity."** Real synthesis is never perfectly clean. Figures of 98–99.9% are realistic; a flat 100% is a warning sign.
- **Ask for the batch CoA before buying** if it is not published. A reputable supplier will provide it.
## Why this matters for research
Impure or misidentified compounds are one of the biggest hidden sources of unreliable results in peptide research. If you cannot trust what is in the vial, you cannot trust the data that comes out of your experiment. Reading the CoA properly is the simplest safeguard against wasted time and irreproducible work.
At Peptide Pal, every research compound is independently verified, with a Certificate of Analysis available on every product page. You can [browse our full range of research peptides](/pages/buy-peptides), explore the [peer-reviewed studies](/pages/studies) behind each compound, or [contact our team](/pages/support) with any question about a specific batch.
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*All compounds supplied by Peptide Pal are strictly for in-vitro laboratory research and are not for human consumption, self-administration, or medical use.*