The proportion of a sample that is the intended compound, as measured by a stated analytical method.
Purity is a measured proportion, normally reported from HPLC peak area. Because it depends on what the method can resolve and detect, purity is only meaningful alongside the method that produced it.
Purity is also not the same as peptide content: a lyophilized solid is not 100% peptide by weight even when the peptide present is highly pure, because counter-ions and bound water contribute mass.
Topic: Lab Practice
A foundational overview of what research peptides are, how laboratories handle them as reference compounds, the difference between in-vitro and preclinical models, and why COAs matter.
Read moreThe counterion can be the largest non-peptide term in a lyophilised solid, and it is not inferable from the sequence. How suppressed-conductivity ion chromatography measures trifluoroacetate, acetate, chloride and the common cations; how to dilute into the linear range; what system suitability to fix for a small anion; and how to read a molar ratio that lands far from expectation.
Read moreNebulisation-based detectors answer a physical question rather than an optical one: how much non-volatile mass reached the detector. What that buys when a sequence has no tryptophan or tyrosine, why the response is a power law, how far mobile-phase composition moves it and what inverse-gradient compensation corrects, and the precise claim a relative mass percent from CAD or ELSD will and will not support.
Read moreA C-terminal aldehyde is electrophilic, epimerises the carbon beside it, and is not a single species in water. How masked precursors carry it through a synthesis, and what the resulting chromatogram and mass spectrum do and do not tell you.
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