Cyano cyanopropyl column

Silica has often been modified with silver for argentation chromatography because of the additional selectivity conferred by the interactions between silver and Jt-bonds of unsaturated hydrocarbons. In a recent example, methyl linoleate was separated from methyl linolenate on silver-modified silica in a dioxane-hexane mixture.23 Bonded phases using amino or cyano groups have proved to be of great utility. In a recent application on a 250 x 1-mm Deltabond (Keystone Scientific Belief onte, PA) Cyano cyanopropyl column, carbon dioxide was dissolved under pressure into the hexane mobile phase, serving to reduce the viscosity from 6.2 to 1 MPa and improve efficiency and peak symmetry.24 It was proposed that the carbon dioxide served to suppress the effect of residual surface silanols on retention. 

Dipolar compounds such as those with chloro, nitro, and nitrile substituents are more strongly retained on cyano columns, compared to amino or diol [14]. Also, cyanopropyl silica can exhibit acidic or basic character, depending on the mobile phase used. It was shown that a complete reversal of elution order was obtained for phenol and anihne when MTBE and chloroform were used as the mobile phases, because phenol eluted first in the MTBE solvent and second in the chloroform solvent [9],... 

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