A COA, or Certificate of Analysis, must refer to a specific batch. HPLC (high-performance liquid chromatography, a purity-testing method) purity, mass spectrometry and mass content do not duplicate one another. Each answers a different question about the sample.
Three lines that are often confused
| Result | What it shows | What it cannot prove on its own |
|---|---|---|
| HPLC purity | The share of the chromatogram signal occupied by the main peak under a stated method | Exact molecular mass, sequence or amount of substance in the vial |
| MS (mass spectrometry) or LC (liquid chromatography)-MS | Whether the observed mass matches the expected mass of the molecule | Purity by peak area or mass fraction of the substance |
| Mass content | The quantitatively assigned amount of target substance in the sample | The full impurity profile without separate chromatographic analysis |
HPLC separates components in a mixture. On a COA, the main peak is usually assigned to the target substance and the other peak areas represent impurities visible to that method. The result depends on the column, mobile phase, wavelength and integration settings. A 99% figure without the chromatogram and method description is therefore less useful than a complete report.
MS measures mass-to-charge ratio and allows the observed mass to be compared with a calculated value. It is a strong mass check, but equal mass does not always mean equal structure. Isomers and some modifications can require additional identity methods.
Mass content is not the same as HPLC purity. HPLC purity commonly expresses relative peak area. Mass content expresses the quantitatively assigned fraction of target substance in the material. Water, residual salts and other non-target components can affect that value even when HPLC purity is high.
Endotoxin: a separate line on the COA
Endotoxin sits on a COA separately from HPLC purity and mass content, because it answers a different question. It is a lipopolysaccharide from the outer membrane of gram-negative bacteria, and chromatographic purity does not reveal it. A sample can show a high HPLC main peak and still contain endotoxin introduced during synthesis or purification.
Endotoxin is measured by the LAL test (gel-clot, chromogenic or turbidimetric variant, harmonised across pharmacopoeias). The result is recorded in EU/mg or EU/mL. A blank field in this line does not mean zero, it means the parameter was not measured.
Why the net peptide content can be lower than the weighed amount
The weight of powder in a vial is not the mass of the target peptide. The counterion from synthesis (for example trifluoroacetic acid or acetate) and residual water are part of the total material mass but are not peptide. So the quantitatively assigned net peptide content is often below the total material mass.
Molecular identity is confirmed separately, usually by LC-ESI-MS with impurity profiling. That check shows what the substance is, while net content shows how much target compound the material contains.
A one-minute COA check
- Match the lot number on the COA, label and verification page. If it is absent or different, the report cannot be assigned to the sample.
- For HPLC, read the numeric result together with the chromatogram and method conditions.
- For MS, compare expected and observed mass. It helps when the report explains charge state or adduct.
- Do not turn one number into three conclusions. HPLC purity, MS identity and mass content are separate checks.
What a readable COA contains
A readable report is tied to a lot, names the methods and shows primary results. If a laboratory supplies only a percentage, ask for the chromatogram, mass spectrum and an explanation of how mass content was assigned.
For Longeva batches, the lot number can be checked on the verification page. A COA confirms characteristics of the tested sample. It does not replace a method description, explain analytical limits or automatically apply to another batch.
The general context of COAs and research-use status is covered separately: research-use peptides and what a COA confirms and why origin and the COA matter more than price. This page is deliberately limited to a few key analytical readouts of a COA and does not claim to be a full list of every method.
What happens before these measurements, that is, how a peptide is actually made before it ever reaches a lab, is covered in the article on peptide synthesis (SPPS) and purification. A short overview of the whole path from synthesis to a certificate is on Tripept's "What peptides are" page.
Certificates of analysis for our batches: COA archive.
What a missing COA tells you
An empty space where the certificate should be is itself a data point. Without a report, no result from working with the sample can be tied to what is actually in the vial: not purity, not identity, not how much of the compound is there. That does not automatically make the material worse. It makes it unverified, which is a different thing.
Several situations read as a missing COA in practice, even when you were shown a file:
- A report with no lot number. A certificate belongs to one specific lot. A document without a lot cannot be tied to your vial.
- One report per catalogue item rather than per batch. Synthesis is repeated, and every run has its own impurity profile. Last year's report says nothing about today's material.
- A picture of a percentage with no method. A line reading "99.3%" with no chromatogram, lab name or test date is not a measurement.
- A report nobody can check. If the laboratory is not named, there is no one to ask for confirmation.
The sensible reaction here is not "do not buy" but "ask for the report". A seller who genuinely tests the material will send it without explaining why that is difficult.
Who actually runs the analysis
One question is worth asking before the purity figure: whose report is this. We send samples for testing ourselves rather than relying on a document from the raw material supplier. The difference matters. A supplier is grading its own work, while an outside laboratory has no such conflict.
Longeva batches are tested by independent third-party laboratories, among them Janoshik, Testides, Uzorak and North American Diagnostics. We deliberately do not describe any of them as accredited. That claim is common in this market and it is not true. Laboratory independence and laboratory accreditation are separate things, and nobody benefits from confusing them.
Matching a lot against the public archive
The batch number is printed on the label, and that is what you search the COA archive with. The archive is open, no account is needed, and an address of the form /en/coa?q= with the lot number pre-fills the search. Batches are accompanied by certificates, which we publish in that archive.
The QR code on the packaging leads to the verification page rather than to one batch's file. That is deliberate: the code is printed before the batch ships, so it opens the verification page, where the number is entered by hand.
Catalogue and verification
See the research peptide catalogue; batches are accompanied by certificates in the open COA archive.
What these checks look like on one specific molecule is shown on the page about retatrutide reviews and data. If you have already received our material and are willing to describe the condition of the parcel, the lot number and whether it matched the COA, you can do that at longeva-review.com.
The method background for these checks is described in the peptide-analytics literature: D'Hondt et al., Journal of Pharmaceutical and Biomedical Analysis, 2014 on related impurities in peptide medicines, De Spiegeleer et al., Analytical Biochemistry, 2008 on impurity profiling by LC-PDA and LC-MS, Tamura et al., Biomedicines, 2021 on LAL technology for endotoxin control, and Colalto, Regulatory Toxicology and Pharmacology, 2024 on the regulatory view of peptide-drug impurities.