Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT 84602, USA.
J Chromatogr A. 2011 Mar 11;1218(10):1399-408. doi: 10.1016/j.chroma.2011.01.028. Epub 2011 Jan 18.
Highly cross-linked networks resulting from single crosslinking monomers were found to enhance the concentrations of mesopores in, and the surface areas of, polymeric monoliths. Four crosslinking monomers, i.e., bisphenol A dimethacrylate (BADMA), bisphenol A ethoxylate diacrylate (BAEDA, EO/phenol=2 or 4) and pentaerythritol diacrylate monostearate (PDAM), were used to synthesize monolithic capillary columns for reversed phase liquid chromatography (RPLC) of small molecules. Tetrahydrofuran (THF) and decanol were chosen as good and poor porogenic solvents for BAEDA-2 and BAEDA-4 monoliths. For the formation of the BADMA monolith, THF was replaced with dimethylformamide (DMF) to improve the column reproducibility. Appropriate combinations of THF, isopropyl alcohol and an additional triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) or PPO-PEO-PPO porogen were found to be effective in forming rigid PDAM monoliths with the desired porosities. Selection of porogens for the BADMA and PDAM monoliths was investigated in further detail to provide more insight into porogen selection. Isocratic elution of alkyl benzenes at a flow rate of 0.3 μL/min was conducted for BADMA and PDAM monoliths. The peaks showed little tailing on both monoliths without addition of acid to the mobile phase. The column efficiency measured for pentylbenzene using the BADMA monolithic column was 60,208 plates/m (k=7.9). Gradient elution of alkyl benzenes and alkyl parabens was achieved with high resolution. Optimized monoliths synthesized from all four crosslinking monomers showed high permeability, and demonstrated little swelling or shrinking in different polarity solvents. Column preparation was highly reproducible; relative standard deviation (RSD) values were less than 1.2% and 7.5% based on retention times and peak areas, respectively, of alkyl benzenes.
通过使用单交联单体形成的高度交联网络，发现其可增加聚合整体柱中的中孔浓度和比表面积。使用四种交联单体，即双酚 A 二甲基丙烯酸酯（BADMA）、双酚 A 乙氧基二丙烯酸酯（BAEDA，EO/苯酚=2 或 4）和季戊四醇二丙烯酸酯单硬脂酸酯（PDAM），合成用于小分子反相液相色谱（RPLC）的整体毛细管柱。选择四氢呋喃（THF）和癸醇作为 BAEDA-2 和 BAEDA-4 整体柱的良好和不良致孔剂。对于 BADMA 整体柱的形成，用二甲基甲酰胺（DMF）代替 THF 以改善柱重现性。发现 THF、异丙醇和外加三嵌段聚（氧化乙烯）-聚（氧化丙烯）-聚（氧化乙烯）（PEO-PPO-PEO）或 PPO-PEO-PPO 致孔剂的适当组合可有效形成具有所需孔隙率的刚性 PDAM 整体柱。进一步详细研究了 BADMA 和 PDAM 整体柱的致孔剂选择，以提供对致孔剂选择的更多了解。以 0.3 μL/min 的流速在 BADMA 和 PDAM 整体柱上进行烷基苯的等度洗脱。在没有向流动相中添加酸的情况下，两种整体柱上的峰均无拖尾。使用 BADMA 整体柱测量戊基苯时的柱效为 60,208 板/m（k=7.9）。实现了烷基苯和烷基对羟基苯甲酸酯的梯度洗脱，具有高分辨率。四种交联单体合成的优化整体柱具有高渗透性，在不同极性溶剂中几乎没有溶胀或收缩。柱制备具有高度重现性；基于烷基苯的保留时间和峰面积的相对标准偏差（RSD）值分别小于 1.2%和 7.5%。
