Methylated cyclodextrin-bonded stationary phases for liquid chromatography

Abstract Ethylenediamine-monosubstituted per-O-methyl-α- and -β-cyclodextrin were coupled to succinamidopropyl silica. The unreacted, terminal carboxyl groups of the resulting methylated cyclodextrin stationary phases do not interact significantly with several disubstituted benzene derivatives having various functional groups. However, the secondary amino —NH— group in the spacer arm linking the cyclodextrin units to silica gel interacts strongly with solutes having small p Ka values, such as aminobenzoic and nitrobenzoic acids. Methylated α-cyclodextrin stationary phases with non-nitrogen-containing spacer arms were prepared by reaction of bare silica gel with two organotrichlorosilanes incorporating methylated α-cyclodextrin. These new stationary phases do not exhibit the strong interaction with the benzoic acids.