title: Evaluation of selectivity for L-glutamide-derived highly ordered assemblies in reversed-phase high-performance liquid chromatography.
abstract: Two dioctadecyl L-glutamic acid derivatives with amide and ester type bondings have been synthesized and immobilized from 3-aminopropyltrimethoxysilane (APS) grafted silica (Sil-APS) to be used in reversed-phase high-performance liquid chromatography (RP-HPLC). Subsequent studies showed that dioctadecyl-L-glutamide derivative (GLN) can self-assemble into highly ordered structures by forming three-dimensional fibrillar aggregates as observed in scanning and transmission electron microscopes (SEM and TEM). Variable temperature (1)H NMR and FT-IR spectra of organogel revealed that the special aggregation morphology shown by GLN was stabilized by inter and or intra molecular hydrogen bonding among amide moieties. However, such ordered aggregated or self-assembled structures were not observed for the dioctadecyl-L-glutamate (GLU) derivative. The stationary phases Sil-GLN and Sil-GLU were characterized by DRIFT, elemental analysis, TGA, and (13)C and (29)Si CP-MAS NMR spectroscopic measurements. The chromatographic selectivity for both stationary phases was evaluated from the retention studies of different size and shape polycyclic aromatic hydrocarbons (PAHs). The chromatographic experiment for PAHs and geometrical isomers in RP-HPLC showed that Sil-GLN demonstrated extremely enhanced selectivity than Sil-GLU. The higher selectivity attributed by Sil-GLN has been brought by multiple pi-pi interactions among the pi-electrons of the grafted organic phase and pi-electrons of the guest PAHs molecules. Thermodynamic studies for linear and nonlinear PAHs revealed that the retention behavior does not change over a temperature range from 10 to 60 degrees C for both stationary phases.
authors.affiliation: Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University, Kumamoto, Japan. mizan607@gmail.com
authors.forename: M Mizanur
authors.initials: MM
authors.lastname: Rahman
authors.forename: Makoto
authors.initials: M
authors.lastname: Takafuji
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ihara
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D018698:Glutamic Acid / Q000031:analogs & derivatives* / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D018698:Glutamic Acid; D012822:Silicon Dioxide