Normal phase eluotropic strength

Relative elution solvent strength (or eluotropic strength) is depicted in solvent polarity charts (Figure 2.39). The relative elution strength for a solvent on a polar, normal-phase sorbent such as silica or alumina increases in reverse order to that measured on a nonpolar, reversed-phase sorbent. Ac-... 

The elution of the solute from a normal-phase sorbent is typically a function of the eluotropic strength and polarity of the eluting solvent. Table 2.1 shows the solvent eluotropic strength and polarity for a range of organic solvents typically used in normal-phase SPE. Silica will adsorb moderately polar... 

The order of solvents is according to increasing eluotropic strength in normal phase chromatography [2). 

Retention volumes in normal-phase chromatography depend much on the polarity and polarizability of the analyte molecules, and little on their molecular masses [42]. Thus, all alkyl benzenes, or all alkyl esters, will be eluted in a narrow range of retention volumes. On the other hand, structural changes affecting the polarity of a molecule are easily seen. The amount of water adsorbed by the stationary phase controls its activity, hence the resolution between analytes, and this is in turn a sensitive function of water dissolved in the mobile phase. Thus, control of the water content of the eluent is a primary concern. The influence of the composition of the mobile phase on retention has been discussed by Snyder, who introduced the concept of eluotropic strength [42],... 

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