Alternative approaches for sample preparation in capillary electrophoresis

In separation science, especially in capillary electrophoresis (CE), the process of sample preparation is often lengthier than the actual separation time and requires specialised equipment and trained personnel in a laboratory environment. Aiming to reduce analytical turn around times by bringing the analytical instrumentation to the sample, we developed a number of alternatives to commonly used sample preparation techniques. Because CE is instrumentally most compatible with the development of portable and field deployable instrumentation, the focus was on the use of CE as separation technique. First, the direct sample injection from fruits and vegetables will be presented [1]. Hydrodynamic effects caused by the separation capillary piercing the fruit were effectively excluded by increasing the hydrodynamic resistance of the separation capillary, enabling the electrokinetic injection from various fruits including zucchini, apple and mushroom. The analytical results correlated well with analysis by ICP-MS. Second, we developed a system for on-line monitoring of suspension cultures by sequential injection capillary electrophoresis [2]. Using only 8.1 mL of media (41 μL per run), the metabolic status and cell density were recorded every 30 minutes over 4 days. Thirdly, an electrokinetic size mobility trap was developed to selectively extract, concentrate and purify pharmaceuticals from whole blood [3]. Using nanojunctions of decreasing poresize, ampicillin, an antibiotic used for the treatment of sepsis, could be analysed from whole blood in less than 5 minutes. With significant differences in their application, these examples demonstrate the feasibility of simplifying sample processing to enable fast and on-site analysis by CE with minimal human intervention.