Novotny Allyson L, Nurok David, Replogle Randall W, Hawkins Gregory L, Santini Robert E
Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 402 North Blackford Street, Indianapolis, Indiana 46202, USA.
Anal Chem. 2006 Apr 15;78(8):2823-31. doi: 10.1021/ac052262v.
Pressurized planar electrochromatography (PPEC) is a fast and efficient planar chromatographic technique. The mobile phase is driven by electroosmotic flow, while the system is pressurized in a manner that allows heat to flow between the sorbent layer and the pressurizing medium. The reproducibility of solute retention was not satisfactory in the initial report describing PPEC. In the current report, this reproducibility is improved by better control of several experimental variables. The pressure at which PPEC is performed is now free of drift, and the temperature at which the layer is preconditioned is maintained to within +/-1 degrees C. The best reproducibility of retention is obtained when the plate is soaked in the mobile phase for a defined time before each run. In the original prototype, the temperature of the sorbent layer was not controlled. In the present apparatus, water, at a constant temperature between 3 and 60 degrees C, is circulated through channels in the two die blocks that pressurize the layer. The highest efficiency is obtained at an intermediate temperature. This behavior is ascribed to high resistance to mass transfer at the lower temperatures and increased diffusion at higher temperatures. Efficiency, as measured by the number of theoretical plates, increases with increasing migration distance. The height equivalent of a theoretical plate diminishes with increasing migration distance, and values as low as 0.0106 mm are obtained under appropriate conditions. This extrapolates to 94 000 plates/m. Manual spotting was used in this report. Evidence is presented that substantially better efficiency would be obtained if the initial spot size were smaller. The efficiency of PPEC in its current form is illustrated by a chromatogram showing the separation of nine solutes in 2 min. PPEC was also performed with TLC plates in a back-to-back configuration, and this doubles the number of samples that can be simultaneously separated.
加压平面电色谱（PPEC）是一种快速高效的平面色谱技术。流动相由电渗流驱动，而系统以允许热量在吸附剂层和加压介质之间流动的方式进行加压。在最初描述PPEC的报告中，溶质保留的重现性并不令人满意。在本报告中，通过更好地控制几个实验变量提高了这种重现性。现在进行PPEC时的压力无漂移，并且层进行预处理的温度保持在±1℃以内。每次运行前将板在流动相中浸泡规定时间可获得最佳的保留重现性。在原始原型中，吸附剂层的温度未得到控制。在本装置中，温度在3至60℃之间恒定的水通过对层进行加压的两个模块中的通道循环。在中间温度下可获得最高效率。这种行为归因于较低温度下传质阻力高以及较高温度下扩散增加。以理论塔板数衡量的效率随迁移距离增加而提高。理论塔板高度随迁移距离增加而减小，在适当条件下可获得低至0.0106mm的值。这外推至94000块塔板/米。本报告中使用手动点样。有证据表明，如果初始点样尺寸更小，将可获得显著更高的效率。以一张在2分钟内分离出9种溶质的色谱图说明了当前形式的PPEC的效率。PPEC也采用背靠背配置在薄层色谱板上进行，这使可同时分离的样品数量增加了一倍。
