For EK injection, a cross-injector and a double-T injector have been constructed. The injection and separation modes for a cross-injector vs. double-T injectors (with the 100 and 250 μm “sampling loop”) were visualized as shown in Figure 4.1.620

The aforementioned injection of a solution plug is termed plug injection. Another sample introduction mode is stack injection. Stack and plug injections used in DNA separation have been compared (see Figure 4.2). Under similar conditions, the plug injection produced a better resolution, whereas the stack injection produced a higher sensitivity (see Chapter 6, Section 6.2 for more on capillary electrophoresis (CE) separation).315