title: Preparation and characterization of surfactin-modified silica stationary phase for reversed-phase and hydrophilic interaction liquid chromatography.
abstract: Surfactants are good candidates as selectors in mixed-mode reversed-phase liquid chromatography (RPLC)/hydrophilic interaction liquid chromatography (HILIC) because they contain both a hydrophobic and a hydrophilic moiety. Surfactin, a cyclic heptapeptide, is an efficient biosurfactant produced by Bacillus subtilis that comprises seven amino acids and a β-hydroxyl fatty acid. A surfactin-modified silica (SMS) stationary phase was prepared by amide bond formation between amino groups on aminopropyl silica and the carboxylic acid groups of L-Glu and L-Asp residues in surfactin. The resulting SMS stationary phase was characterized in both RPLC and HILIC mode using different mobile phases. The SMS column was found to separate analytes in both modes. The retention of polar solutes exhibited "U-shaped" curves, depending on the acetonitrile content. "U-shaped" curves are an indicator of RPLC/HILIC mixed-mode retention behavior. The presence of hydrophobic and hydrophilic moieties in surfactin provides unique properties that allow the SMS column to be used for both RPLC and HILIC separations, simply by changing the mobile phase composition.
authors.affiliation: Course of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Japan.
authors.forename: Kaname
authors.initials: K
authors.lastname: Ohyama
authors.affiliation: Course of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Course of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Japan.
authors.forename: Naoya
authors.initials: N
authors.lastname: Kishikawa
authors.affiliation: Course of Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Japan. Electronic address: n-kuro@nagasaki-u.ac.jp.
authors.forename: Naotaka
authors.initials: N
authors.lastname: Kuroda
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D056148:Chromatography, Reverse-Phase / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D012822:Silicon Dioxide
keywords: Hydrophilic interaction; Mixed-mode; Reversed-phase; Surfactin