Centre for Bioanalytical Sciences, National Centre for Sensor Research, Dublin City University, Glasnevin, Dublin 9, Ireland.
Analyst. 2009 Jul;134(7):1314-21. doi: 10.1039/b901300h. Epub 2009 Apr 3.
Capacitively coupled contactless conductivity detection (C4D) is utilised as a simple, rapid and non-invasive technique for the quantitative evaluation of the ion-exchange capacity of charged polymer monoliths in capillary format. A charged monomer, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was photografted onto a 100 microm i.d. butyl methacrylate-co-ethylenedimethacrylate monolith in a number of discrete 10 mm zones. By varying the energy dose (J/cm2) during grafting of each zone, the grafting density and thus ion-exchange capacity could be precisely controlled. Ion-exchange capacity could be correlated with energy dose by measuring the conductive response of each grafted region using scanning C4D techniques. Repeatability of the scanning C4D method was excellent with % RSD values of 0.7% and 2.4% obtained for three replicate scans of the ungrafted and grafted regions of a single monolith, respectively. Repeatability of the photografting process on separate monoliths was also examined by comparison of C4D profiles. The spatial accuracy of photografting was probed using scanning C4D which could measure the conductive response of the monolith at measurement intervals as low as 1 mm along its entire length. Scanning C4D was also used for the real time visualisation of the equilibration of grafted zones to permit the optimisation of monolith washing procedures. Finally, scanning C4D was applied to the measurement of the ion-exchange capacity of butyl methacrylate-co-AMPS-co-ethylenedimethacrylate copolymers with a direct correlation between monolith conductive response and concentration of charged monomer in the polymerisation mixture. The longitudinal homogeneity of charge along the monolith was 0.3% RSD, demonstrating that the charged functional monomer was evenly dispersed throughout the bulk of the monolith. Ion-exchange capacity was cross validated chromatographically using breakthrough studies and found to closely correlate to within 1% of the measurements made by scanning C4D.
电容耦合非接触式电导检测 (C4D) 被用作一种简单、快速和非侵入式的技术，用于定量评估带电荷聚合物整体柱的离子交换容量。在许多离散的 10mm 区域中，将带电单体 2-丙烯酰胺基-2-甲基-1-丙磺酸 (AMPS) 光接枝到 100μm id 的丁基甲基丙烯酸酯-乙二甲基丙烯酸酯整体柱上。通过在每个区域的接枝过程中改变能量剂量 (J/cm2)，可以精确控制接枝密度，从而控制离子交换容量。通过使用扫描 C4D 技术测量每个接枝区域的导电响应，可以将离子交换容量与能量剂量相关联。扫描 C4D 方法的重复性非常好，对于单个整体柱的未接枝和接枝区域的三个重复扫描，分别获得了 0.7%和 2.4%的 %RSD 值。通过比较不同整体柱的 C4D 图谱，还检查了光接枝过程的重复性。使用扫描 C4D 探测光接枝的空间精度，该方法可以在整个长度上以低至 1mm 的测量间隔测量整体柱的导电响应。扫描 C4D 还用于实时可视化接枝区域的平衡，以优化整体柱洗涤程序。最后，扫描 C4D 用于测量丁基甲基丙烯酸酯-AMPS-乙二甲基丙烯酸酯共聚物的离子交换容量，整体柱的导电响应与聚合混合物中带电单体的浓度之间存在直接相关性。电荷沿着整体柱的纵向均匀性为 0.3%RSD，表明带电功能单体均匀分散在整体柱的大部分体积中。通过使用突破研究进行色谱学交叉验证，发现离子交换容量与扫描 C4D 测量值密切相关，相差不超过 1%。
