Eluting power:
The eluting power of a solvent is determined by its whole polarity, a polarity of the stationary phase, and the nature of sample elements. The capacity factor, k′, is controlled through the strength of solvent that could be easily predicted in adsorption chromatography. Snyder has defined solvent strength parameter, εo, as the adsorption energy per unit area of adsorbent.
Some common solvents used in adsorption chromatography are listed in Table 8.6 in the order of increasing solvent strength. It also includes adsorption strength of the various functional groups of solute molecules. Such a list is also called eluotropic series of solvents. It has been observed that log k′ for a given solute varies linearly with εo. Other properties of solvents which must be taken into account include boiling point and viscosity, flammability detector compatibility, and toxicity. Generally, the lower boiling and therefore, the low viscosity solvents give higher chromatographic efficiency and lower back pressure.