Forced flow overpressured developing chamber

Figure 7.19 Chronpes 25 overpressure development chamber for forced-flow TLC. The configuration shown is for on-line detection. 

Figure 8.19 illustrates another example of the versatility of multidimensional OPLC, namely the use of different stationary phases and multiple development ("D) modes in combination with circular and anticircular development and both off-line and on-line detection (37). Two different stationary phases are used in this configuration. The lower plate is square (e.g. 20 cm X 20 cm), while the upper plate (grey in Figure 8.19) is circular with a diameter of, e.g. 10 cm. The sample must be applied on-line to the middle of the upper plate. In the OPLC chamber the plates are covered with a Teflon sheet and pressed together under an overpressure of 5 MPa. As the mobile phase transporting a particular compound reaches the edge of the first plate it must-because of the forced-flow technique-flow over to the second (lower) stationary phase, which is of lower polarity. 

Empore silica sheet, because of its physical characteristics, cannot used in a conventional chamber system over 5 cm development distance (62). Due to the forced flow OPLC makes a longer development distance and rapid separation possible on this sorbent. This is promoted also by the higher density of sheet caused by overpressure (63). 

---