Peak Integration
Definition
Deciding where a peak starts and stops so its area can be calculated. Where the baseline is drawn changes the number, which is why integration parameters belong in the method rather than in the analyst's judgement on the day.
In more detail
Integration is the step between the trace and the number: software decides where each peak begins and ends, drops a baseline underneath it, and calculates the area above that line.
Where the baseline is drawn is a real choice, and on a partly resolved pair or a drifting baseline it changes the reported percentage. This is why integration parameters belong in the written method rather than being left to whoever processed the run, and why an audit trail that records reprocessing matters: a result that was integrated several times until it passed looks identical to one that was integrated once.
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
Reversed-Phase HPLC (RP-HPLC)
The chromatographic mode almost all peptide purity work uses: a non-polar stationary phase with a polar moving phase, separating components by hydrophobicity. The gradient usually runs water and acetonitrile with an acidic modifier.
HPLC-UV
High-performance liquid chromatography with an ultraviolet detector, typically reading at 214 nm where the peptide bond absorbs. It reports how much of the absorbing material is the target peak, which is a purity measurement and not an identity one.
LC-MS
Liquid chromatography coupled to a mass spectrometer, so each separated component is also weighed. It answers identity and purity in one run, which HPLC-UV alone cannot: a UV detector cannot tell two compounds apart if they elute together.
Tandem Mass Spectrometry (MS/MS)
Selecting one ion, fragmenting it, and measuring the fragments. The fragment pattern is far more specific than mass alone, which is why certificates quote transitions rather than a single mass for confirmation.
Electrospray Ionisation (ESI)
The soft ionisation technique that gets peptides into a mass spectrometer intact, by spraying the solution through a charged needle. It tends to produce several charge states of one molecule rather than a single ion.
Mass-to-Charge Ratio (m/z)
What a mass spectrometer actually measures: mass divided by charge, not mass. A 4,000 Da peptide carrying three charges appears near m/z 1,334, which is why a raw spectrum rarely shows the molecular weight directly.
Charge State
How many charges an ion carries in the mass spectrometer. Peptides commonly appear in several at once, and the series of peaks they produce is what allows the true molecular mass to be calculated.
Deconvolution
The arithmetic that turns a series of multiply-charged peaks back into one molecular mass. It is the step between what the instrument recorded and the single number printed on a certificate.