Boonsong Kanokporn, Caulum Meghan M, Dressen Brian M, Chailapakul Orawon, Cropek Donald M, Henry Charles S
Sensor Research Unit, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
Electrophoresis. 2008 Aug;29(15):3128-34. doi: 10.1002/elps.200800186.
The effect of successive multiple ionic layer (SMIL) coatings on the velocity and direction of EOF and the separation efficiency for PDMS electrophoresis microchips was studied using different polymer structures and deposition conditions. To date, the majority of SMIL studies have used traditional CE and fused-silica capillaries. EOF was measured as a function of polymer structure and number of layers, in one case using the same anionic polymer and varying the cationic polymer and in the second case using the same cationic polymer and varying the anionic polymer. In both situations, the EOF direction reversed with each additional deposited polymer layer. The absolute EOF magnitude, however, did not vary significantly with layer number or polymer structure. Next, different coatings were used to compare separation efficiencies on native and SMIL-coated PDMS microchips. For native PDMS microchips, the average separation efficiency was 4105 +/- 1540 theoretical plates. The addition of two layers of polymer increased the separation efficiency anywhere from two- to five-fold, depending on the polymer structure. A maximum separation efficiency of 12 880 +/- 1050 theoretical plates was achieved for SMIL coatings of polybrene (cationic) and dextran sulfate (anionic) polymers after deposition of six total layers. It was also noted that coating improved run-to-run consistency of the peaks as noted by a reduction of the RSD of the EOF and separation efficiency. This study shows that the use of polyelectrolyte coatings, irrespective of the polymer structure, generates a consistent EOF in the current experiments and dramatically improves the separation efficiency when compared to unmodified PDMS microchips.
采用不同的聚合物结构和沉积条件，研究了连续多层离子层（SMIL）涂层对聚二甲基硅氧烷（PDMS）电泳微芯片电渗流（EOF）的速度和方向以及分离效率的影响。迄今为止，大多数SMIL研究都使用传统的毛细管电泳和熔融石英毛细管。在一种情况下，以聚合物结构和层数为函数测量EOF，使用相同的阴离子聚合物并改变阳离子聚合物；在另一种情况下，使用相同的阳离子聚合物并改变阴离子聚合物。在这两种情况下，随着每增加一层沉积的聚合物，EOF方向都会反转。然而，EOF的绝对大小并没有随层数或聚合物结构而显著变化。接下来，使用不同的涂层来比较天然PDMS微芯片和SMIL涂层PDMS微芯片的分离效率。对于天然PDMS微芯片，平均分离效率为4105±1540理论塔板数。添加两层聚合物可使分离效率提高两到五倍，这取决于聚合物结构。在总共沉积六层后，聚凝胺（阳离子）和硫酸葡聚糖（阴离子）聚合物的SMIL涂层实现了12880±1050理论塔板数的最大分离效率。还注意到，涂层改善了峰的批间一致性，这表现为EOF和分离效率的相对标准偏差（RSD）降低。本研究表明，在当前实验中，无论聚合物结构如何，使用聚电解质涂层都会产生一致的EOF，并且与未改性的PDMS微芯片相比，显著提高了分离效率。
