Purity vs. net-peptide content: what the number actually means.
Two peptide vials can both say “99% pure” and hold wildly different amounts of peptide. That's not a contradiction — it's the difference between purity and content, and it's the most commonly confused thing on a peptide COA. Here's the distinction, and why it changes how you read a certificate.
Purity answers “how clean,” not “how much”
Chromatographic purity is the area-percent of your target peak relative to everything else the analysis resolves. A 99% purity result means that, of what the column separated and the detector saw, 99% was your compound and 1% was other resolved material. It's a statement about quality — how much of what's in the vial is the thing you wanted, versus impurities.
What purity does not tell you is how much peptide is actually there. It's a ratio, not a quantity. A nearly empty vial and a full one can both be 99% pure.
Net-peptide content answers “how much”
Net-peptide content (also called net-peptide assay) is the actual mass of peptide in the vial, in milligrams, quantified against a certified reference standard. This is the number that tells you whether a vial labeled “10 mg” contains 10 mg — or 7.
This matters because peptide isn't the only thing in a lyophilized vial. Counterions, residual water, and excipients all add mass. A vial can weigh the “right” amount on a scale and still be well short on actual peptide. Purity won't catch that. Only a content assay will.
Why a 99% pure vial can still be underfilled
Imagine a vial that's genuinely 99% pure by HPLC — the peptide present is clean. But it was filled with 6 mg of peptide, not the 10 mg on the label, with the rest of the vial mass made up of salt and water. Purity: excellent. Content: 40% short. A purity-only COA on that vial would have said everything looked perfect — and the label would still be 40% wrong.
That's the gap. Purity describes the quality of the peptide that's present; content describes how much peptide is present. You need both numbers to know what you actually have.
Why KMD reports both
On every certificate, KMD reports chromatographic purity (area %) and net-peptide assay (mg per vial), alongside a reference-standard identity confirmation — all by RP-HPLC-UV, against certified reference standards. We report the milligram figure because a purity percentage alone leaves the most practical question — how much peptide did I actually get? — unanswered.
And because every COA we issue is SHA-256 verifiable, those numbers can't be quietly edited after the fact without the tampering being detectable.
How content is judged — and what “conforms” means
A milligram figure needs a rule to be judged against, and the rule should be on the certificate. KMD's content specification is a floor: the measured net-peptide content must be at least 90% of the label claim. There is deliberately no upper cap — a vial that holds more than its label says is reported as exactly that, not marked as a failure, because an overfill is information the buyer wants, not a defect to hide. The specification is printed beside the result, and content counts toward the certificate's overall conformance alongside identity and purity. Purity itself is printed to two decimal places, never rounded to a friendlier number.
Blends make the distinction sharper. In a vial with more than one active — a GLOW, a Wolverine, a CJC-1295/Ipamorelin — there is no such thing as the vial's purity or the vial's content. Each active is resolved as its own peak and gets its own purity and its own milligrams, judged against its own share of the label, so a short component cannot hide inside a healthy-looking total. A blend certificate with a single purity number has answered a question nobody asked. How the identity side of that works is in how peptide identity is confirmed.