The effect of charged groups on hydrophilic monolithic stationary phases on their chromatographic properties.
In order to investigate the effect of charged groups present in hydrophilic monolithic stationary phases on their chromatographic properties, three charged hydrophilic monomers, i.e. N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA), [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETA), and 3-sulfopropyl acrylate potassium salt (SPA) were co-polymerized with the crosslinker N,N'-methylenebisacrylamide (MBA), respectively. The physicochemical properties of the three resulting charged hydrophilic monolithic columns were evaluated using scanning electron microscopy, ζ-potential analysis and micro-HPLC. High column efficiency was obtained on the three monolithic columns at a linear velocity of 1mm/s using thiourea as test compound. Comparative characterization of the three charged HILIC phases was then carried out using a set of model compounds, including nucleobases, nucleosides, benzoic acid derivatives, phenols, β-blockers and small peptides. Depending on the combination of stationary phase/mobile phase/solute, both hydrophilic interaction and other potential secondary interactions, including electrostatic interaction, hydrogen-bonding interaction, molecular shape selectivity, could contribute to the over-all retention of the analytes. Because of the strong electrostatic interaction provided by the quaternary ammonium groups in the poly (AETA-co-MBA) monolith, this cationic HILIC monolith exhibited the strongest retention for benzoic acid derivatives and small peptides with distorted peak shapes and the weakest retention for basic β-blockers. The sulfonyl groups on the poly (SPA-co-MBA) hydrophilic monolith could provide strong electrostatic attraction and hydrogen bonding for positively charged analytes and hydrogen-donor/acceptor containing analytes, respectively. Therefore, basic drugs, nucleobases and nucleotides exhibited the strongest retention on this anionic monolith. Because of the weak but distinct cation exchange properties of the zwitterionic poly (SPDA-co-MBA) hydrophilic monolith, it exhibited the best separation for most test analytes (including phenols, β-blockers and small peptides) in terms of selectivity, peak shape and analysis time. The poly (AETA-co-MBA) hydrophilic monolithic column provides the best separation of nucleobases and nucleosides. These results could guide the selection and application of these charged HILIC monoliths in the future.
Institute of Pharmaceutical Analysis, College of Pharmacy, Jinan University, Guangzhou, Guangdong, 510632, China.
Haibin
H
Li
Institute of Pharmaceutical Analysis, College of Pharmacy, Jinan University, Guangzhou, Guangdong, 510632, China.
Chusheng
C
Liu
Institute of Pharmaceutical Analysis, College of Pharmacy, Jinan University, Guangzhou, Guangdong, 510632, China.
Qiqin
Q
Wang
Institute of Pharmaceutical Analysis, College of Pharmacy, Jinan University, Guangzhou, Guangdong, 510632, China. Electronic address: haibo.zhou@jnu.edu.cn.
Haibo
H
Zhou
Institute of Pharmaceutical Analysis, College of Pharmacy, Jinan University, Guangzhou, Guangdong, 510632, China. Electronic address: jzjjackson@hotmail.com.
Zhengjin
Z
Jiang
D000178:Acrylamides / Q000737:chemistry*; D000179:Acrylates / Q000737:chemistry*; D001565:Benzoates / Q000032:analysis; D001622:Betaine / Q000031:analogs & derivatives* / Q000737:chemistry; D002853:Chromatography, Liquid / Q000295:instrumentation* / Q000379:methods; D003432:Cross-Linking Reagents / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D009705:Nucleosides / Q000032:analysis; D009711:Nucleotides / Q000032:analysis; D010455:Peptides / Q000032:analysis; D010636:Phenols / Q000032:analysis; D058105:Polymerization; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D055672:Static Electricity; D013438:Sulfhydryl Compounds / Q000737:chemistry*
C000617094:3-sulfopropyl acrylate potassium salt; D000178:Acrylamides; D000179:Acrylates; D001565:Benzoates; D003432:Cross-Linking Reagents; C000617092:N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine; D009705:Nucleosides; D009711:Nucleotides; D010455:Peptides; D010636:Phenols; D000644:Quaternary Ammonium Compounds; D013438:Sulfhydryl Compounds; C000617093:(2-(acryloyloxy)ethyl)trimethylammonium chloride; D001622:Betaine; C021221:N,N'-methylenebisacrylamide
Charged group; Electrostatic interaction; Hydrogen bonding; Hydrophilic interaction chromatography; Zwitterionic monolithic column