How we verify every batch: HPLC, Mass Spec & Endotoxin

A vial of white powder tells you nothing on its own. Everything a researcher needs to trust — what the compound is, how pure it is, and whether it’s clean of contaminants — comes from analysis, not from a label. Before any MrPep batch is released for sale it passes three independent tests. Here’s what each one does.

1. HPLC — how pure is it?

High-Performance Liquid Chromatography (HPLC, usually reverse-phase with UV detection around 214 nm) separates everything in a sample by how strongly each component sticks to a column. The target peptide comes off at its own time and shows up as a peak on a chromatogram. Purity is simply the area of that main peak divided by the area of all peaks, expressed as a percentage.

A clean result looks like a single dominant peak — a high number such as 99.9% — with only tiny satellite peaks. What HPLC cannot tell you is whether that big peak is the compound you ordered. For that, you need the second test.

2. Mass Spec — what is it, exactly?

Mass spectrometry (typically LC-MS) measures the molecular weight of the compound and compares it to the expected value for that exact sequence. If the measured mass matches — often to within a fraction of a part-per-million — the identity is confirmed. HPLC tells you how pure; Mass Spec tells you what it is. You need both, which is exactly the subject of our companion article, Purity vs identity.

3. Endotoxin (LAL) — is it clean?

Endotoxins are fragments from bacterial cell walls that can survive long after the bacteria are gone. A Limulus Amebocyte Lysate (LAL) test measures them and reports a quantitative result in endotoxin units per millilitre (EU/mL), with a clear pass/fail against a threshold. It’s a safety-and-quality screen that HPLC and Mass Spec don’t cover.

Purity, identity and endotoxin answer three different questions. A batch has to pass all three before it earns the word “verified”.

Independent, by design

We use independent third-party laboratories that do not sell peptides. That matters: a lab with no commercial stake in the result has no reason to flatter a number. Each batch’s results are published to a public certificate, and the certificate is linked from the product page and from our Verify a Batch tool so anyone can check it — no account required.