title: Characterization of C18-bonded liquid chromatographic stationary phases by Raman spectroscopy: the effect of mobile phase composition.
abstract: Raman spectroscopy is used to examine the effect of mobile phase composition on the orientation of octadecyl-bonded silica-based reversed-phase liquid chromatographic (RPLC) stationary phase ligands. The effect of ligand bonding density is also investigated. The present experimental set-up utilizes a direct, noninvasive, on-column approach to examine the solvent dependent conformational behavior of the bonded ligands under flow-rate and back pressure conditions similar to those used during conventional RPLC measurements. Neat, single-component, mobile phase solvents including water, acetonitrile, methanol and chloroform are used to investigate the hypothesized collapsing and extension of stationary phase ligands with changes in mobile phase composition. No evidence of phase collapse was observed upon changing the mobile phase composition from an organic to an aqueous content. Also, Raman spectroscopic measurements allowed the differentiation between associated and free acetonitrile solvent.
authors.affiliation: Department of Chemistry, University of Cincinnati, OH 45221-0172, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Doyle
authors.forename: T J
authors.initials: TJ
authors.lastname: Vickers
authors.forename: C K
authors.initials: CK
authors.lastname: Mann
authors.forename: J G
authors.initials: JG
authors.lastname: Dorsey
mesh_terms: D002725:Chloroform / Q000737:chemistry; D002853:Chromatography, Liquid / Q000295:instrumentation*; D008024:Ligands; D000432:Methanol / Q000737:chemistry; D008968:Molecular Conformation; D012997:Solvents / Q000737:chemistry; D013059:Spectrum Analysis, Raman
chemical_list: D008024:Ligands; D012997:Solvents; D002725:Chloroform; D000432:Methanol