Which phase in chromatography typically retains the sample longer?

In chromatography, the stationary phase is the component that retains the sample longer. This is because the stationary phase is fixed in place and typically has interactions with the sample molecules, such as adsorption or partitioning, which affect how long the sample spends in that phase before it is eluted or carried away by the mobile phase.

In a typical chromatographic setup, the mobile phase flows over the stationary phase, carrying the sample along with it. However, different components of the sample will interact with the stationary phase to varying degrees, causing some to be retained longer than others based on their respective affinities for the stationary material. This principle is fundamental to the separation of compounds in chromatography, where the varying retention times allow for the separation of different species in the mixture based on their chemical properties.

Thus, the stationary phase is critical in determining the effectiveness of the separation process, serving as a medium that selectively interacts with the compounds being analyzed, ultimately enhancing resolution and separation in chromatographic techniques.