Purity and content answer different questions
Purity asks what share of the detected material is the target peptide. Content asks how many milligrams of it are in the vial. A sample can pass one and fail the other: highly pure but underfilled, or correctly filled with a significant impurity. They are separate measurements, and a certificate reporting only a percentage is silent on quantity. Purity versus content, in detail.
Reading the result
- Content against label uses measured values only. It needs a measured content figure, which is a separate test rather than part of a standard purity analysis.
- Target peptide in the powder multiplies declared figures. Treat it as a cross-check of a supplier’s specification, not as a result.
- The calculator never estimates a value that was not measured, and none of these figures establish safety or suitability for use.
Questions
Is peptide purity the same as how much peptide is in the vial?
No. HPLC area purity is the share of detected UV signal in the main peak. A vial can be 99% pure and still hold less peptide than its label, because purity says nothing about mass. The amount of peptide is a separate measurement, reported as content.
How do I calculate content against the label claim?
Divide the measured content by the labelled amount and multiply by 100. A 10 mg vial measured at 9.6 mg is 96% of its label claim.
What is net peptide content?
Lyophilized peptide powder also contains counter-ions (such as acetate or TFA) and residual water. Net peptide content is the share of the powder mass that is peptide. Multiplying gross powder mass by net peptide content and by purity estimates the target peptide mass, but only a content measurement confirms it.
What purity is acceptable for a research peptide?
There is no universal number. Acceptance depends on the specification you are testing against, and a purity result should always be read together with identity confirmation and measured content.