For Research Use Only. Not for human consumption. This guide explains how to read a Certificate of Analysis (COA) for any research peptide, from any supplier. It does not address dosing, administration, or recommendations for use.
What a COA Actually Is
A Certificate of Analysis (COA) is a laboratory document issued after a specific production batch, or “lot,” of material has been tested. It reports what the lab actually found — not what the product is generally expected to be. Peptide synthesis is a chemical manufacturing process, and even under tightly controlled conditions, purity and trace impurity profiles can vary slightly from one lot to the next. That is why a COA is tied to a lot number rather than to a product name: a purity claim not linked to a specific batch tells a researcher very little about the material actually in front of them.
Most researchers encounter two analytical methods on a COA: HPLC and LC-MS. Understanding what each one measures — and, just as importantly, what it does not measure — is the difference between reading a COA and just glancing at a purity percentage.
The Five Fields Every COA Should Show
Documentation quality varies widely across the research peptide industry. At minimum, a rigorous COA should include:
| Field | What It Tells You |
|---|---|
| Batch/Lot Number | Uniquely identifies the specific production run — this is what you match against the physical label on your unit. |
| Purity Percentage | The measured chromatographic purity, typically from HPLC peak-area analysis. |
| Test Date | When the analysis was performed, so you can judge how current the documentation is. |
| Testing Method / Laboratory | Which analytical method(s) were used (HPLC, LC-MS, or both) and, ideally, which lab performed the work. |
| Molecular Weight / Identity Confirmation | Where LC-MS is used, confirms the measured mass matches the expected mass for that exact sequence. |
If a COA is missing a lot number, a test date, or any indication of which method produced the purity figure, that is a real gap in the documentation — not a formatting choice.
How to Read the HPLC Section
High-Performance Liquid Chromatography (HPLC) separates a sample’s components as they pass through a column, most commonly a C18 reversed-phase column, using a water–acetonitrile solvent gradient. A UV detector, typically set around 214 nm — a wavelength peptide bonds absorb strongly — records each component as it exits the column, producing a chromatogram made up of distinct peaks. Purity by HPLC is generally calculated as the area of the main compound peak divided by the total integrated peak area, expressed as a percentage.
A single, sharp, symmetrical peak is generally a strong quality signal. But HPLC purity reflects the relative proportion of UV-absorbing material in that main peak — on its own, it does not confirm the molecular identity of the peak, and it does not directly measure residual moisture, salt, or counterion content that can be present in a lyophilized sample (Creative Proteomics). That gap is exactly what the second method is for.
How to Read the LC-MS Section
Liquid Chromatography–Mass Spectrometry (LC-MS) pairs the same chromatographic separation with mass spectrometry detection. As the sample elutes from the column, it is ionized — commonly by electrospray ionization — and a mass spectrometer measures the mass-to-charge ratio of the resulting ions, from which the compound’s molecular mass is calculated and compared against the theoretical mass for that exact sequence.
LC-MS gives a researcher two things HPLC alone cannot: identity confirmation, meaning the tested material’s mass actually matches the compound it is labeled as, and the ability to flag mass-shifted variants — from oxidation, deamidation, or incomplete synthesis — that can hide inside what looks like a single clean HPLC peak (Creative Proteomics). When a COA reports both a purity percentage and a matching molecular weight, you are looking at a genuinely complete quality picture rather than half of one.
What “99% Purity” Actually Means
When a COA reports 99% purity, it means HPLC analysis found that 99% of the UV-absorbing material detected in the sample corresponds to the main compound peak, with the remaining 1% attributable to trace synthesis byproducts or related impurities. On its own, that number says nothing about identity. Paired with an LC-MS result confirming the expected molecular weight, a 99% purity figure becomes a verifiable, not just asserted, claim — the two data points together are what actually support confidence in a batch, not either one alone.
A Worked Example: Reading a Real COA
Here is what this looks like applied to an actual batch record. One of the lots in our own catalog, MOTS-c 10mg, lot number AX-MS10-072726-001, was tested by Freedom Diagnostics using HPLC-UV and LC-MS, with results reported August 23, 2026. The COA lists a purity of 99.74%, meaning HPLC found that 99.74% of the detected material corresponded to the main compound peak. Because the same COA also includes an LC-MS-confirmed molecular weight matching the expected mass for MOTS-c’s sequence, that purity figure is backed by an identity check, not just a chromatography readout in isolation.
Reading any COA, from any supplier, comes down to the same four questions: Does the lot number on the document match the lot number on your physical label? Is there a test date, and is it reasonably recent? Was the purity figure produced by HPLC, and is there a separate LC-MS identity confirmation? And does the reported molecular weight actually match the compound’s known mass? If the answer to all four is yes, you are holding a COA that does what a COA is supposed to do.
Finding and Verifying Your Own COA
Every product listed on Ascenyx Bio includes a COA download link directly on its product page, organized by lot number. To verify your specific unit: locate the lot number printed on your product’s label, visit the corresponding product page, download the COA matching that lot number, and confirm the batch number, purity percentage, and test date all line up with what is printed on your physical product. The same four checks apply whether you are reviewing our documentation or a COA from any other supplier. See our Quality & Testing page for our full testing standards, or browse the COA Library directly.
A Note on Regulatory Status
All compounds referenced on this page are sold strictly as Research Use Only (RUO) materials. They are not approved by the FDA as drugs, biologics, dietary supplements, or medical devices, and are not intended for diagnostic, therapeutic, cosmetic, or any human or animal use. RUO is a recognized regulatory labeling category for materials intended solely for laboratory and analytical research (U.S. FDA guidance on RUO/IUO labeling). This guide is limited to explaining analytical testing methodology and documentation; it does not address dosing, administration, or any question tied to human or animal use. Researchers with questions along those lines should direct them to a qualified institutional or medical professional, not a vendor content page.