Why are the bands drawn as Gaussians?

Under linear chromatography with many random partitioning steps, the zone shape approaches a Gaussian by the central-limit theorem. Real peaks can front or tail when isotherms are nonlinear; the cartoon assumes the ideal symmetric case.

What makes two compounds separate?

They spend different average times adsorbed on or dissolved in the stationary phase, so their effective velocities differ. Separation grows with distance traveled, while diffusion and mass-transfer broaden peaks — resolution is the trade-off between those effects.

Is this HPLC, GC, or TLC?

It is a generic partition-column cartoon, not a specific instrument model. The same retention-versus-broadening intuition applies across liquid and gas chromatography; hardware details are omitted on purpose.

Chromatography Column

Partition chromatography cartoon: Gaussian bands separate as retention on the stationary phase differs.

About this model

A partition-chromatography cartoon shows analyte bands migrating down a column as Gaussian peaks. Different retention on the stationary phase produces different migration speeds, so bands separate in space and time. Peak width grows as the bands travel, illustrating dispersive broadening alongside separation. The model is schematic: linear partition coefficients, Gaussian zones, and no detailed van Deemter plate-height theory, gradient elution, or nonlinear isotherms. Mobile-phase flow is idealized as steady and one-dimensional. You observe how relative retention splits a mixture into resolved peaks and how longer travel increases both separation and broadening — the qualitative idea behind column chromatography in analytical chemistry.

Who it's for: General and analytical chemistry students meeting chromatographic separation for the first time.

Key terms

Chromatography
Retention
Stationary phase
Mobile phase
Gaussian peak
Band separation

How it works

Schematic partition chromatography: analytes equilibrate between mobile and stationary phases; stronger affinity for the stationary phase moves more slowly and exits later.

Key equations

Retention increases with partition coefficient K = C_s / C_m (toy model uses distinct effective band speeds).

Frequently asked questions

Why are the bands drawn as Gaussians?: Under linear chromatography with many random partitioning steps, the zone shape approaches a Gaussian by the central-limit theorem. Real peaks can front or tail when isotherms are nonlinear; the cartoon assumes the ideal symmetric case.
What makes two compounds separate?: They spend different average times adsorbed on or dissolved in the stationary phase, so their effective velocities differ. Separation grows with distance traveled, while diffusion and mass-transfer broaden peaks — resolution is the trade-off between those effects.
Is this HPLC, GC, or TLC?: It is a generic partition-column cartoon, not a specific instrument model. The same retention-versus-broadening intuition applies across liquid and gas chromatography; hardware details are omitted on purpose.