How is the total volume (Vt) defined in chromatography?

The total volume (Vt) in chromatography is best defined as the total volume of the column, including the void volume. This encompasses not only the space within the packed stationary phase where interactions with the sample molecules occur but also the space that is unoccupied by the stationary phase, which is filled with the mobile phase.

In chromatography, the void volume is the volume in which molecules can pass through the column without any interaction with the stationary phase. The total volume provides a comprehensive understanding of the column capacity and is critical for understanding how different molecules will elute during the separation process.

This characterization is essential in determining how various compounds, depending on their size and affinity for the stationary phase, will migrate and elute from the column. Therefore, the correct definition of Vt captures all the space available in the column for the liquid mobile phase and any solute molecules therein, rather than just focusing on the elution characteristics of specific molecular sizes.