Characterization of Amino-, Cyano-alkyl Bonded Silica Columns in Normal-Phase Liquid Chromatography by Using Steroids

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Abstract
In order to characterize the chemically bonded phases in HPLC analysis, the retention behavior of fifteen steroids including estrogen, androgen, progestogen and corticoid were systematically examined using dioxan as the stronger component in an n-hexane-binary system. A linear relationship between the logarithm of the capacity ratio and logarithm of the molar concentration of the binary solvent was confirmed for amino- and cyano-type bonded as well as non-bonded silica gel columns. Based on the retention indices of these phases, the retentivity of the packing materials was determined as follows: the amino-type is similar to and the cyano-type is weaker (0.7 times) than bare silica gel when using dioxan as the stronger component. The specific retentivity of an amino column for polar steroids containing phenolic and alcoholic hydroxyl groups suggests a molecular interaction associated with hydrogen bonding between the polar packing surface and solute compounds. The selectivity of amino packing was found to be larger than cyano packing whose retention selectivity is similar to a bare silica gel.