title: Aniline-modified porous graphitic carbon for hydrophilic interaction and attenuated reverse phase liquid chromatography.
abstract: Most stationary phases for hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) are based on silica. Porous graphitic carbon (PGC) is an attractive alternative to silica-based phases due to its chemical and thermal stability, and unique selectivity. However, native PGC is strongly hydrophobic and in some instances excessively retentive. PGC particles with covalently attached aniline groups (Dimethylaniline-PGC and Aniline-PGC) were synthesized to alter the surface polarity of PGC. First, the diazonium salt of N,N-dimethyl-p-phenylenediamine or 4-nitroaniline was adsorbed onto the PGC surface. The adsorbed salt was reduced with sodium borohydride and (Aniline-PGC only) the nitro group was further reduced with iron powder to the aniline. X-ray photoelectron spectroscopy confirmed the surface functionalities and that these moieties were introduced to the surface at concentrations of 0.9 and 2.1molecules/nm(2), respectively. These modified PGC phases (especially Aniline-PGC) were evaluated as HILIC and reversed phases. The Dimethylaniline-PGC phase displayed only weak HILIC retention of phenolic solutes. In contrast, the Aniline-PGC phase displayed up to nearly a 7-fold increase in HILIC retention vs. an aniline-silica phase and selectivity that differed from 10 other HILIC phases. Introduction of aniline groups to the PGC surface reduced the RPLC retentivity of PGC up to more than 5-fold and improved the separation efficiency up to 6-fold. The chromatographic performance of Aniline-PGC is demonstrated by separations of nucleotides, nucleosides, carboxylic acids, basic pharmaceuticals, and other compounds.
authors.affiliation: Department of Chemistry, University of Alberta, Gunning/Lemieux Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada.
authors.forename: Chad D
authors.initials: CD
authors.lastname: Iverson
authors.affiliation: Department of Chemistry, University of Alberta, Gunning/Lemieux Chemistry Centre, Edmonton, Alberta T6G 2G2, Canada. Electronic address: charles.lucy@ualberta.ca.
authors.forename: Charles A
authors.initials: CA
authors.lastname: Lucy
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D056148:Chromatography, Reverse-Phase / Q000295:instrumentation* / Q000379:methods; D057927:Hydrophobic and Hydrophilic Interactions; D056951:Photoelectron Spectroscopy; D016062:Porosity; D013499:Surface Properties
chemical_list: D000814:Aniline Compounds; D002244:Carbon; C023650:aniline
keywords: Diazonium modification; HILIC; Porous graphitic carbon; Reversed phase chromatography