Every peptide,
read down to the molecule.
Peptides are not simple molecules, and generic supplement panels miss what matters. Assay runs the full peptide-specific workup: purity, identity, strength, and the injectable-grade safety tests. Here is exactly what each one measures, and why it decides whether a batch is safe to ship.
A clean label is not a clean vial.
Synthesis is imperfect
Every coupling step can leave truncated or deletion sequences that look almost identical to the target. Only chromatography separates them.
The label is not the dose
Lyophilized peptide carries water and counter-ions. A vial marked 10 mg may hold 8 mg of actual peptide, so dosing depends on net content.
Injectables raise the stakes
Anything reconstituted and injected must clear endotoxins and sterility. Contaminants harmless to swallow can be dangerous in a syringe.
Purity
The sample is pushed through a column that separates molecules by how strongly they stick to it. Each compound leaves the column at its own time and registers as a peak. Divide the area of the main peak by the area of every peak and you get the purity percentage.
Why it matters
Purity tells you how much of the vial is the peptide you actually want, versus closely related junk from synthesis. A tall, sharp, lonely main peak is the signature of a clean batch.
Identity and mass
A mass spectrometer weighs the molecule. Every peptide has an exact mass set by its amino acid sequence, so if the measured mass matches the theoretical mass, the identity is confirmed. MS/MS goes further and reads the sequence itself.
Why it matters
Purity proves the sample is clean; identity proves it is the right molecule. A vial can be 99% pure and still be the wrong or scrambled peptide. This is the anti-counterfeit test, and the one most sellers skip.
Net peptide content
Net content answers a blunt question: how many milligrams of actual peptide are in the vial? Freeze-dried peptide is never pure powder. It carries water, counter-ions like acetate or TFA, and residual salts, all of which add weight.
Why it matters
It is the difference between an accurate protocol and a guess. Reconstitute a 10 mg vial that holds only 8 mg of peptide, and every dose is 20% under. No other test catches this.
Heavy metals
An argon plasma at roughly 6,000°C strips the sample into individual atoms so a mass spectrometer can count metal atoms one by one, down to parts per billion. Lead, arsenic, cadmium, and mercury are the headline four.
Why it matters
Heavy metals accumulate in the body and are toxic at tiny doses. They creep in from reagents, catalysts, glassware, and raw materials. Injectable-intent peptides are held to the tightest limits.
Bacterial endotoxins
Endotoxins are fragments of the outer wall of gram-negative bacteria. The LAL assay uses a reagent derived from horseshoe crab blood that reacts in their presence, measuring concentration in Endotoxin Units per milligram.
Why it matters
This is the test for injectables. Endotoxins are not alive, so they survive sterilization, and even a sterile solution can be pyrogenic: capable of triggering fever, inflammation, or shock. A peptide can pass sterility and still fail here.
Sterility and bioburden
Bioburden counts the viable microorganisms in a sample; sterility testing confirms their absence entirely. Together they cover living contamination: bacteria, yeast, and mold.
Why it matters
Live contamination in an injectable is a direct infection risk. Sterility and endotoxins are complementary: one covers the living organisms, the other the toxic residue they leave behind. Serious peptide programs run both.
The details that separate a spec sheet from a guarantee.
Counter-ion (TFA / acetate)
Peptides ship as a salt. Purification often leaves trifluoroacetate, which is cytotoxic at high levels. We report which counter-ion it carries and how much. Acetate is the gentler form.
Water content
Freeze-dried peptide still holds moisture. Too much water shortens shelf life, invites degradation, and skews the net-content math. Reported as a weight percent.
Residual solvents
Traces of synthesis solvents like acetonitrile and methanol must sit under ICH Q3C safety limits, which matters most for anything injected.
Appearance and reconstitution
Color, clarity, cake integrity, complete dissolution, and pH. The cheapest, first signal that something is off before the instruments confirm it.
How to read a peptide COA.
Here is a full certificate of analysis, the way Assay presents it: every test, its result, the spec it is judged against, and a plain verdict.
| Test | Method | Result | Spec | Verdict |
|---|---|---|---|---|
| Appearance | Visual | White cake | White / off-white | Pass |
| Purity | RP-HPLC | 99.2% | ≥ 98.0% | Pass |
| Identity | LC-MS | 1620.9 Da | 1620.8 Da | Pass |
| Net content | Quant. HPLC | 86.4% | ≥ 80% | Pass |
| Water | Karl Fischer | 3.1% | ≤ 6.0% | Pass |
| Acetate | IC | 4.8% | Report | Pass |
| Heavy metals | ICP-MS | Under limits | USP <232> | Pass |
| Endotoxin | LAL | 0.9 EU/mg | ≤ 17.5 | Pass |
| Sterility | USP <71> | No growth | Sterile | Pass |
Representative values for illustration. Real COAs carry the executing lab's accreditation, method detail, and instrument data.
Put your peptides under the instrument.
Send us a batch and get the full peptide workup back in days, with a transparency panel your customers can actually read. Your first test is on us.