Glossary
Net peptide content
Also called NPC, Peptide content, Assay, Content vs label, Quantity per vial
The share of a powder's weight that is actually peptide, after water, salts and counterions are excluded. It tells you how much peptide is really in the vial.
In more detail
Peptide powders are never 100% peptide by weight. Leftover water (peptides attract moisture), salts and counterions like TFA from purification make up the rest. HPLC purity does not count these, so a sample can be 99% pure and still hold noticeably less peptide than its gross weight.
Some lab reports state a measured amount per vial ("content" or "quantity"), which is the number to compare against the label. A 10 mg label with a measured 8 mg means your doses are about 20% lower than the math assumes.
Why it matters
Purity tells you what is in the vial; content tells you how much. For dosing, content is the number that changes your units. See How to read a peptide lab report (COA).
Related terms
- HPLC purityThe share of the peptide signal in a sample that is the target peptide, measured by high-performance liquid chromatography. It is the percentage most COAs lead with.
- Certificate of analysis (COA)A document from a testing lab that reports what was measured in a sample: usually identity, purity and sometimes amount and contamination tests.
- Mass spectrometryA test that measures the mass of molecules. On a peptide COA it confirms identity: the measured mass should match the expected mass of the peptide.
Sources
Each source is labeled by where the information comes from. How we label sources
- Vendor guideWhat is peptide purity?(opens in a new tab)
LifeTein · checked
- Reference workCertificate of analysis(opens in a new tab)
Wikipedia · checked
Updated