Characterization of liquid chromatographic stationary phases by Raman spectroscopy. Effect of ligand type.
This study represents the first Raman spectroscopic characterization of conventional chemically-bonded liquid chromatographic (LC) stationary phases under typical flow-rate and pressure conditions. Raman spectra were obtained for amino propyl (NH2), cyano propyl (CN), phenyl (Ph), octadecyl (C18), octyl (C8), and methyl (C1) chemically-bonded silica-based stationary phases in 100% aqueous mobile phases. The present experimental set-up has allowed Raman spectra of various stationary phase ligands, present in sub-monolayer coverages on the siliceous supports, to be obtained. This study: (1) demonstrates that conventional Raman spectroscopic techniques can be used to study LC stationary phases; (2) presents the experimental set-up, conditions, and approaches utilized to obtain Raman spectra of conventional stationary phases; (3) examines the spectroscopic differences observed for a variety of different types of bonded ligands that are typically used in reversed-phase (RPLC) and normal-phase (NPLC) liquid chromatographic separations; and (4) considers other future studies that are possible with this experimental approach, including mobile phase composition and temperature studies.
Doyle
C A
CA
Department of Chemistry, University of Cincinnati, OH 45221-0172, USA.
Vickers
T J
TJ
Mann
C K
CK
Dorsey
J G
JG
D002853:Chromatography, Liquid / Q000295:instrumentation / Q000379:methods*; D008024:Ligands; D013059:Spectrum Analysis, Raman
D008024:Ligands