How to read a certificate of analysis.
Every serious peptide vendor talks about COAs. Very few customers are ever shown how to read one — which suits some vendors just fine. Ten minutes here fixes that permanently.
A certificate of analysis is a laboratory's written record of what it measured in a specific batch of material. Read properly, it answers four questions about the vial in your hand: is this the right molecule, how pure is it, how much is actually in there, and is it clean enough to use. Read carelessly, it's a decorative PDF. This guide goes section by section.
First: is the report actually about your vial?
Before any chemistry, check the paperwork's plumbing. A meaningful COA names the compound, a batch or lot number, the analysis date, and the laboratory that performed the testing. That lot number must match the one printed on your vial's label — that match is the entire chain of custody. A “representative” COA with no lot number, or one dated years before the product existed, tells you about a different batch at best and nothing at worst. This is the single most common trick in the research-peptide market: a real report, endlessly reused.
Identity: the right molecule.
Identity is confirmed by mass spectrometry. The instrument weighs the molecule — and a peptide's mass is a fingerprint. BPC-157 has a molar mass around 1,420 g/mol; if the observed mass matches the theoretical mass within instrument tolerance, the chain that was synthesized is the chain that was ordered. On the report, look for a theoretical (calculated) mass beside an observed mass. A missing identity section means the lab never checked that the white powder is the compound on the label — purity of an unidentified substance is a meaningless number.
Purity: how much of the peptide content is the right peptide.
Purity comes from high-performance liquid chromatography. The dissolved sample is pushed through a separation column; the target peptide emerges at its characteristic time and registers as a peak, while truncated chains and synthesis by-products emerge at other times as their own peaks. Purity is the target peak's share of the total peak area — 99.2% purity means 99.2% of what the detector saw was the intended molecule.
On the chromatogram itself: one dominant, sharp peak with a quiet baseline is the picture of a clean synthesis. A cluster of neighbouring peaks, or a purity figure with no chromatogram attached, deserves skepticism. Purity has its own subtleties — what the number does and doesn't include, and why two vendors' “99%” can mean different things — which we cover in peptide purity, explained.
Quantity: how much is really in the vial.
A 10 mg vial should contain ten milligrams of peptide, but lyophilized cakes also carry water and counter-ions, and a careless (or cynical) fill can be far off the label. The quantity assay — gravimetric or by UV absorbance — reports measured content. This is the test that catches underfilled vials, and it's conspicuously absent from most of the market's COAs. If your work depends on knowing concentrations, and all quantitative work does, this section is not optional. Our own standard is that a vial's fill is verified per batch; see how we test.
Endotoxin and sterility: clean enough to use.
Endotoxins are fragments of bacterial cell walls — vanishingly small amounts distort immune-adjacent and cell-culture experiments, and they survive processes that kill the bacteria themselves. The LAL (limulus amebocyte lysate) assay quantifies them, reported in endotoxin units per milligram; every Sentir batch must come in under 0.5 EU/mg. Sterility culturing answers the related question — whether anything living made it into the vial. Both tests concern what's in the vial besides the peptide, which is precisely what a purity number cannot tell you.
The red-flag checklist.
- No lot number, or a lot number that doesn't match the vial label.
- Purity claimed without a chromatogram, or identity claimed without an observed mass.
- A “manufacturer's COA” from the supplier's own lab, re-badged — independent means a third party did the measuring.
- Round, identical numbers across every product in the catalog (every compound exactly “99.9%”) — real measurements vary.
- No endotoxin section anywhere. It's the test cheap vendors skip first, because customers ask about it last.
- A vendor that won't produce the batch report when asked. The report exists or it doesn't; hesitation is the answer.
The test of a vendor is not whether the word “COA” appears on their site — it's whether the document behind it survives this checklist. Ours are included with every order, and the full report for any vial is available by emailing the lot number on its label to [email protected].
Common questions.
Not necessarily — that's the catch. A COA is just a certificate; the question is who did the analysis. A manufacturer can issue a COA about its own material. Third-party testing means an independent laboratory with no stake in the result performed the measurements, which is the standard every Sentir batch is held to.
Every Sentir vial has a lot number printed on its label. Email that number to [email protected] and the full batch report — chromatogram included — is sent within one business day. A copy also ships with every order.
Endotoxin units per milligram of peptide — a measure of bacterial endotoxin contamination from the LAL assay. Below 0.5 EU/mg is a strict reagent-grade threshold; many vendors don't test endotoxin at all.
