Reversedphase Chromatography

Nonpolar adsorbents have rarely been applied in TLC of alkaloids, perhaps because of the low efficiency of such systems, which is caused by the interaction of alkaloid molecules with silanol groups present on the adsorbent surface in addition to the hydrocarbon chains. In reversed-phase chromatography on silanized silica gel, alkaloids as easily ionized compounds require specific conditions of analysis such as suppression of dissociation, ion suppression or the application of specific ion pair reagents.

The suppression of dissociation is achieved with a mobile phase of a suitable pH (pH > pKa) for the specific solvent, in accordance with the curve shown in Figure 2.

Reversed-phase conditions may also be obtained by impregnating silica gel with paraffin or silicone oil. Additionally, chemically bonded reversed phases with polar groups (cyano- and amino-layers) have been employed. Their properties depend on the kind of compounds to be separated and on the composition of the mobile phase.

Solar Panel Basics

Solar Panel Basics

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