Abstract
A new hydrophilic and nonionic poly(2-vinyloxazoline)-grafted silica (Sil-VOX n ) phase was synthesized and applied for the separation of nucleosides and nucleobases in hydrophilic interaction chromatography (HILIC). Polymerization and immobilization onto silica were confirmed by using characterization techniques including 1H NMR spectroscopy, elemental analysis, and diffuse reflectance infrared Fourier transform spectroscopy. The hydrophilicity or wettability of Sil-VOX n was observed by measuring the contact angle (59.9°). The chromatographic results were compared with those obtained with a conventional HILIC silica column. The Sil-VOX n phase showed much better separation of polar test analytes than the silica column, and the elution order was different. Differences in selectivity between these two columns indicate that the stationary phase cannot function merely as an inert support for a water layer into which the solutes are partitioned from the bulk mobile phase. To elucidate the interaction mechanism, the separation of dihydroxybenzene isomers was performed on both columns in normal-phase liquid chromatography. Sil-VOX n was very sensitive to the dipole moments of the positional isomers of polycyclic aromatic compounds in normal-phase liquid chromatography. The interaction mechanism for Sil-VOX n in HILIC separation is also described.
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Acknowledgments
This work was supported by the Grant-in-Aid for Regional Innovation Strategy Support Program and in part by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. The authors thank Kojin Film and Chemicals for proving the 2-vinyloxazoline monomer as a gift.
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Mallik, A.K., Cheah, W.K., Shingo, K. et al. Highly hydrophilic and nonionic poly(2-vinyloxazoline)-grafted silica: a novel organic phase for high-selectivity hydrophilic interaction chromatography. Anal Bioanal Chem 406, 4585–4593 (2014). https://doi.org/10.1007/s00216-014-7868-7
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DOI: https://doi.org/10.1007/s00216-014-7868-7