Purity
Definition
The proportion of a sample that is the intended peptide rather than related impurities, measured chromatographically and quoted as a percentage. It says nothing about identity, sterility or endotoxin content, each of which is a separate test. Volta releases every batch against a >99% HPLC specification.
In more detail
Purity is a measured property of one lot by one method, and the method is part of the claim. A figure from reversed-phase HPLC at 214 nm is a statement about the proportion of ultraviolet-absorbing material that was the target peak.
It is distinct from a specification, which is a threshold set in advance and applies to every lot released against it. A site stating a purity standard of greater than 99% is describing where its release line sits; a certificate reporting 99.4% is describing what one laboratory measured on one batch.
Things the figure does not cover are worth naming: water, counterion and salts the detector never saw, any impurity that co-eluted with the target, and anything that does not absorb at the wavelength used.
Terms used in this definition
Other entries this definition refers to.
Where this term comes up
Entries whose definition mentions Purity.
What this means for research sourcing
Purity and identity verification are central to research reproducibility. Every Volta compound ships with >99% HPLC-verified purity and a certificate of analysis.
Related Terms in Quality
Endotoxin
Lipopolysaccharide from the outer membrane of Gram-negative bacteria. It survives ordinary sterilisation and is not removed by filtration alone, and it provokes a febrile inflammatory response, which is why it is assayed separately from sterility.
LAL Test (Limulus Amebocyte Lysate)
The endotoxin assay, which uses a clotting cascade from horseshoe crab blood that endotoxin triggers. A result on a certificate is a quantity against a limit, not a yes or no.
Sterility Testing
Incubation of a sample in growth media to confirm no viable microorganism is present. Sterility is a property of a validated process and its container and is independent of chemical purity: a very pure material can be non-sterile and often is.
Sterility
The absence of viable microorganisms in a preparation. It is conferred by a process and preserved by a closure, so it is lost the moment either is compromised and nothing about the appearance of a vial reports that.
Assay
Any procedure that measures whether something is present, how much of it there is, or how active it is. Analytical assays report composition; functional assays report activity, and a material can pass one and fail the other.
Quality Control (QC)
The testing a batch passes through before release, typically identity by mass spectrometry, purity by HPLC, content and, where relevant, water, sterility and endotoxin. QC is the set of tests; the certificate is the report of their results.
Degradation Product
A compound formed as a peptide breaks down, through oxidation, deamidation, hydrolysis or aggregation. Certificates report these as impurity peaks, and their pattern says more about how a batch was handled than the headline purity figure does.
Reference Standard
A well-characterised sample run alongside an unknown so that retention time and response can be compared against something known. Without one, a chromatogram shows separation but supports no identification.
