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?:abstract
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A precursor carboxy-silica support was introduced for grafting retentive ligands for use in HPLC. This support was prepared by sequentially reacting 5 µm silica particles with vinyltrimethoxysilane and then thioglycolic acid. The carboxy-silica thus obtained was subsequently functionalized with octadecylamine, 2-naphthylamine or 2-aminoanthracene by on-column reactions via a carbodiimide conjugation reaction. The carbodiimide with its zero-length carboxyl-to-amine coupling ability works by activating the surface carboxyl groups of the precursor support for direct reaction with the primary amines of octadecylamine, 2-naphthylamine or 2-aminoanthracene via amide bond formation. These reactions series, which are applied for the first time in HPLC column fabrication, yielded the octadecyl-, naphthyl- and anthracenyl-silica columns. The three columns were evaluated for their reversed-phase chromatography retention properties with alkylbenzenes, alkylphenyl ketones, nitroalkanes, benzene and toluene derivatives, polyaromatic hydrocarbons and nitro-substituted amino acids. The naphthyl- and anthracenyl-silica exhibited a good selectivity and efficiency towards most of the aromatic analytes when compared to the octadecyl-silica. Nitro-substituted amino acids containing electron withdrawing groups showed greater selectivity than other analytes on the aromatic-based columns than the C18 column. This is because of the ability of the π electron system of the analyte to accept electrons from the aromatic-based stationary phase (a Lewis base). This article is protected by copyright. All rights reserved.
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