Copolymer-grafted silica phase from a cation-anion monomer pair for enhanced separation in reversed-phase liquid chromatography.
This work reports a new imidazolium and L-alanine derived copolymer-grafted silica stationary phase for ready separation of complex isomers using high-performance liquid chromatography (HPLC). For this purpose, 1-allyl-3-octadecylimidazolium bromide ([AyImC18]Br) and N-acryloyl-L-alanine sodium salt ([AAL]Na) ionic liquids (IL) monomers were synthesized. Subsequently, the bromide counteranion was exchanged with the 2-(acrylamido)propanoate organic counteranion by reacting the [AyImC18]Br with excess [AAL]Na in water. The obtained IL cation-anion monomer pair was then copolymerized on mercaptopropyl-modified silica (Sil-MPS) via a surface-initiated radical chain-transfer reaction. The selective retention behaviors of polycyclic aromatic hydrocarbons (PAHs), including some positional isomers, steroids, and nucleobases were investigated using the newly obtained Sil-poly(ImC18-AAL), and octadecyl silylated silica (ODS) was used as the reference column. Interesting results were obtained for the separation of PAHs, steroids, and nucleobases with the new organic phase. The results showed that the Sil-poly(ImC18-AAL) presented multiple noncovalent interactions, including hydrophobic, π-π, carbonyl-π, and ion-dipole interactions for the separation of PAHs and dipolar compounds. Only pure water was sufficient as the mobile phase for the separation of the nucleobases. Ten nucleosides and bases were separated, using only water as the mobile phase, within a very short time using the Sil-poly(ImC18-AAL), which is otherwise difficult to achieve using conventional hydrophobic columns such as ODS. The combination of electrostatic and hydrophobic interactions are important for the effective separation of such basic compounds without the use of any organic additive as the eluent on the Sil-poly(ImC18-AAL) column.
Department of Applied Chemistry and Biochemistry, Faculty of Engineering, Kumamoto University, 2-39-1 Kurokami, Kumamoto, 860-8555, Japan.
Abul K
AK
Mallik
Hongdeng
H
Qiu
Makoto
M
Takafuji
Hirotaka
H
Ihara
D000409:Alanine / Q000737:chemistry; D000838:Anions; D002412:Cations; D002623:Chemistry Techniques, Analytical; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D009705:Nucleosides / Q000737:chemistry; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013256:Steroids / Q000737:chemistry; D013696:Temperature
D000838:Anions; D002412:Cations; D007093:Imidazoles; D007477:Ions; D009705:Nucleosides; D011084:Polycyclic Aromatic Hydrocarbons; D011108:Polymers; D013256:Steroids; D012822:Silicon Dioxide; D000409:Alanine