The principle involved in paper chromatography is

Paper chromatography is primarily a form of partition chromatography [2]. The principle involves the distribution of components between two liquid phases: a stationary phase and a mobile phase. In this technique, water molecules trapped within the cellulose pores of the filter paper act as the stationary liquid phase, while a solvent (or mixture of solvents) acts as the mobile phase. As the mobile phase travels up the paper via capillary action, the solutes separate based on their differential partition coefficients between these two phases. While adsorption can occasionally occur if the solid surface of the paper interacts directly with the solute, the standard scientific classification for paper chromatography is partition chromatography [2]. This distinguishes it from techniques like thin-layer chromatography (TLC), which are often based on adsorption [2].

Sources

1. [2] https://www.sciencedirect.com/topics/biochemistry-genetics-and-molecular-biology/paper-chromatography