Why do different substances travel at different speeds during chromatography?

In chromatography, substances travel at different speeds because they distribute themselves differently between a moving mobile phase and a stationary phase.12

The separation is driven by the competition between the mobile phase, which transports the solutes, and the stationary phase, which exerts a resistive force through intermolecular forces such as dispersion, polar attraction, or hydrogen bonding. Components with a higher affinity for the stationary phase are held back and travel more slowly, while those with a stronger affinity for the mobile phase are transported more rapidly.231

In specific cases like size-exclusion chromatography, the speed of travel is determined by molecular size rather than chemical affinity. Larger molecules are excluded from the porous structure of the stationary phase and move through the system faster, while smaller molecules enter the pores and are retained longer. Ultimately, these differences in migration rates allow for the effective separation of complex mixtures.452