Retention Time
Definition
How long a component takes to travel through the column and reach the detector. It is characteristic of a compound under fixed conditions, which is why identity is often confirmed by a sample and a reference standard eluting at the same time.
In more detail
Under fixed conditions a compound leaves the column at a characteristic time, so retention time is the first evidence of identity a chromatographic run produces. A sample peak and a reference standard peak arriving at the same time is consistent with them being the same compound.
Consistent is not the same as proven. Many compounds share a retention time on any given method, which is why identity is confirmed with a second, orthogonal measurement rather than with timing alone. Mass spectrometry is the usual partner because it reads a different property entirely.
Retention time is a property of the method as much as of the compound. Change the column chemistry, the gradient, the temperature or the flow rate and the number moves, which is why a certificate quoting a retention time has to quote the conditions with it.
Terms used in this definition
Other entries this definition refers to.
Where this term comes up
Entries whose definition mentions Retention Time.
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
Co-elution
Two components leaving the column together and arriving as one peak. It is the main way a purity figure can be honestly measured and still be too high, and it is why an orthogonal method is worth running.
Peak Integration
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.
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.