HPLC (High-Performance Liquid Chromatography)
Definition
The separation technique behind the purity figure on a certificate. A sample is pushed through a packed column under pressure and the components come off at different times, so a 99% result means 99% of what the detector saw was the target peak.
In more detail
A sample is dissolved, injected into a stream of solvent and pushed through a column packed with fine particles. Components that interact more strongly with the packing move more slowly, so a mixture that entered as one plug arrives at the detector spread out in time. The detector records a trace, and each component appears on it as a peak.
The purity figure quoted for a peptide is almost always area percent from this trace: the target peak's area divided by the total area of all peaks, at a wavelength where the peptide bond absorbs. That phrasing matters. It is a statement about the proportion of what the detector saw, not about the proportion of what is in the vial, and anything the detector cannot see does not appear in the denominator.
Salts, water and residual solvents are the usual invisible fraction. A lyophilised peptide that is 99% pure by HPLC can still be a minority of the powder by mass once counterion and water are counted, which is why net peptide content is measured separately and reported as its own figure.
On a certificate
A purity percentage, the wavelength it was read at, the column and gradient, and ideally the chromatogram itself so the baseline and the integration can be seen rather than taken on trust.
Where this term comes up
Entries whose definition mentions HPLC (High-Performance Liquid Chromatography).
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
Chromatography
Any technique that separates a mixture by how its components distribute between a moving phase and a stationary one. Reversed-phase liquid chromatography is the version peptide work almost always means.
Mass Spectrometry (MS)
Measurement of the mass-to-charge ratio of ionised molecules, used to confirm that the observed mass matches the mass the sequence predicts. It supports identity; on its own it does not prove the full sequence, since rearrangements can share a mass.
Amino Acid Analysis (AAA)
Hydrolysing a peptide back to its constituent amino acids and quantifying each one, which gives composition and total peptide content. It answers a question HPLC does not: how much peptide is actually in the vial.
Net Peptide Content
The share of the powder that is peptide, once counter-ions and residual water are accounted for. Gross vial weight is always higher, so purity and content are two separate numbers and neither substitutes for the other.
Karl Fischer Water Determination
The standard laboratory assay for water content in a dry solid, using an iodine reaction specific to water. On a lyophilised peptide it reports residual moisture, which is a stability predictor, and the result is reported as a mass fraction of water in the solid.
Purity
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.
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.
