Van Deemter equation

The Van Deemter equation relates chromatographic plate height to the linear velocity of the mobile phase. Its terms describe how different sources of band broadening make column efficiency depend on flow rate.

Eddy diffusion: Band broadening caused by molecules taking different paths through a packed chromatographic column. This is the equation’s flow-independent A term for packed columns.
Chromatography: A separation technique in which components distribute differently between a mobile phase and a stationary phase. The equation describes efficiency within this family of separation methods.
High-performance liquid chromatography: A liquid-chromatography method that pumps pressurized mobile phase through a packed column of small particles. Its operating velocity and particle packing shape the terms governing plate height.
J. J. van Deemter: Dutch chemical engineer whose name is attached to an influential equation for chromatographic plate height. He co-authored the 1956 paper that established the equation’s familiar form.
Longitudinal diffusion: Band broadening caused by solute molecules diffusing along the column’s length. This B/u contribution grows in importance as mobile-phase velocity decreases.
Mobile phase: The fluid that moves through a chromatographic system and carries sample components. Its linear velocity is the independent variable in the equation.
Gas chromatography: A chromatographic method that uses a gas as the mobile phase to separate volatile compounds. The equation’s classic use includes selecting carrier-gas velocity for efficient separations.
F. J. Zuiderweg: Dutch chemical engineer who co-authored the 1956 paper presenting the Van Deemter equation. His collaboration helped derive the relationship between flow velocity and plate height.
Mass transfer: The movement of a substance between phases or regions, often at a finite rate. Finite equilibration between mobile and stationary phases produces the high-velocity contribution.
Stationary phase: The phase held in place in chromatography, with which sample components interact during separation. Interactions with this phase contribute to finite mass transfer.

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