Retention time in HPLC is the time taken by a compound to pass through the column and reach the detector after being injected into the system.
Simple explanation:
- When a sample mixture is injected, its components travel through the column at different speeds.
- Each compound interacts differently with the stationary phase and the mobile phase.
- Because of these differences, each compound comes out of the column at a different time.
- The time from the injection to when a compound’s peak appears on the chromatogram is called its retention time (tᵣ).
Key points:
- It is measured in minutes or seconds.
- Each compound has a unique retention time under the same conditions.
- Retention time helps in identifying compounds and comparing their behavior.
- It depends on factors like:
- Type of column and stationary phase
- Flow rate of the mobile phase
- Temperature
- Solvent composition
In simple words:
Retention time is how long a compound stays inside the HPLC column before coming out.
Different compounds have different retention times, which helps separate and identify them.