NUCLEAR-MAGNETIC-RESONANCE AND ELECTRON-SPIN-RESONANCE SPECTROSCOPIC INVESTIGATIONS OF REVERSED-PHASE LIQUID-CHROMATOGRAPHIC RETENTION MECHANISMS - STATIONARY-PHASE STRUCTURE

Recent studies have demonstrated that stationary phase structure and conformation play important roles in reversed-phase liquid chromatographic (RPLC) behavior. Nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopic techniques can provide a unique perspective for studying RPLC stationary phases. They not only provide information about the types of molecular dynamics and interactions ongoing at the stationary phase surface, but also about their temporal domains. This paper reviews NMR and ESR spectroscopic studies that have been performed to better understand the structure and mobility of RPLC stationary phases. The effects of ligand morphology, mobile phase composition and temperature on alkyl chain mobility and conformation are discussed. The advantages and limitations of spectroscopic techniques for these types of investigations are also reviewed.