Lämmerhofer Michael, Tobler Ernst, Zarbl Elfriede, Lindner Wolfgang, Svec Frantisek, Fréchet Jean M J
Institute of Analytical Chemistry, University of Vienna, Vienna, Austria.
Electrophoresis. 2003 Sep;24(17):2986-99. doi: 10.1002/elps.200305527.
A new chiral monomer derived from cinchona alkaloid, namely O-9-(tert-butylcarbamoyl)-11-[2-(methacryloyloxy)ethylthio]-10,11-dihydroquinine 1, was employed for the preparation of enantioselective monolithic capillary columns by an in situ copolymerization with 2-hydroxyethyl methacrylate 2 (HEMA), ethylene dimethacrylate 3 (EDMA) in the presence of cyclohexanol and 1-dodecanol as porogens (UV or thermal initiation of azobisisobutyronitrile (AIBN) as radical initiator). The porous properties and the electrochromatographic behavior of the new chiral monoliths were comparatively evaluated with previously described analogs obtained from O-9-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine 4 as chiral monomer. Despite close structural and physicochemical similarities of the both chiral monomers, the pore distribution profiles of the resulting monoliths were shifted typically towards larger pore diameters with the new monomer 1. Once more, it was confirmed that a low cross-linking (10 wt% related to total monomers) and a pore diameter of about 1 microm in the dry state provides the best electrochromatographic efficiency as a result of lower resistance to mass transfer (smaller C-term contribution to peak broadening) and more homogeneous flow profile (smaller A-term). Most importantly, as expected the new poly(1-co-HEMA-co-EDMA) monoliths showed enhanced enantioselectivities and in addition faster separations as compared to poly(4-co-HEMA-co-EDMA) analogs, which represents a significant improvement. Further, the elution order was reversed owing to the pseudoenantiomeric behavior of quinine- and quinidine-derived monomers. Fluorescence-labeled 9-fluorenylmethoxycarbonyl (FMOC), dansyl (DNS), 7-dimethylaminosulfonyl-1,3,2-benzoxadiazol-4-yl (DBD), carbazole-9-carbonyl (CC) amino acids could be separated with resolution values between 2 and 4 (with efficiencies typically between 100,000 and 200,000 plates/m) and fluorescence detection (variable wavelength fluorescence detector in-line with UV) yielding routinely a gain in detection sensitivities up to two orders of magnitude without specific optimization of the conditions with regards to fluorescence efficiency.
一种源自金鸡纳生物碱的新型手性单体，即O - 9 -（叔丁基氨基甲酰基）- 11 - [2 -（甲基丙烯酰氧基）乙硫基]- 10,11 - 二氢奎宁1，被用于通过在环己醇和1 - 十二烷醇作为致孔剂存在下与甲基丙烯酸2 - 羟乙酯2（HEMA）、二甲基丙烯酸乙烯酯3（EDMA）原位共聚来制备对映选择性整体式毛细管柱（以偶氮二异丁腈（AIBN）作为自由基引发剂进行紫外或热引发）。将新型手性整体柱的多孔性质和电色谱行为与先前描述的以O - 9 - [2 -（甲基丙烯酰氧基）乙基氨基甲酰基]- 10,11 - 二氢奎尼定4作为手性单体得到的类似物进行了比较评估。尽管这两种手性单体在结构和物理化学性质上相近，但使用新型单体1时，所得整体柱的孔径分布曲线通常向更大的孔径偏移。再次证实，低交联度（相对于总单体为10 wt%）以及干燥状态下约1微米的孔径，由于较低的传质阻力（对峰展宽的C项贡献较小）和更均匀的流动分布（较小的A项），提供了最佳的电色谱效率。最重要的是，正如预期的那样，与聚（4 - co - HEMA - co - EDMA）类似物相比，新型聚（1 - co - HEMA - co - EDMA）整体柱表现出更高的对映选择性，并且分离速度更快，这是一个显著的改进。此外，由于奎宁和奎尼定衍生单体的假对映体行为，洗脱顺序发生了反转。荧光标记的9 - 芴甲氧羰基（FMOC）、丹磺酰基（DNS）、7 - 二甲基氨基磺酰基 - 1,3,2 - 苯并恶二唑 - 4 - 基（DBD）、咔唑 - 9 - 羰基（CC）氨基酸能够以2至4的分辨率值（效率通常在100,000至200,000理论塔板数/米之间）进行分离，并且通过荧光检测（与紫外联用的可变波长荧光检测器），在不针对荧光效率进行特定条件优化的情况下，通常能使检测灵敏度提高两个数量级。
