Capillary Chromatography - Back Flushing Techniques 1

Back flushing Techniques


The back flushing system utilizes an eight port valve in the layout depicted in figures 20 (sample injection) and 21 (back flushing).



Figure 20. Sample Injection in the Back Flushing Procedure

Many sample often contain very highly retained solutes that can contaminate the column, or, at the very least, result in very long analysis times. This problem can be obviated by reversing the flow of carrier gas through the column after the solutes of interest have been eluted. This procedures removes the strongly retained solutes and will be accomplished in approximately the same time it took to elute the solutes of interest. This procedure prevents accumulation of contaminating material at the front of the column at the cost of merely doubling the actual analysis time. If the temperature is raised during the back flushing procedure then the time for contaminant removal will be much less. However, it should be noted, that more time will then be required to bring the column temperature back to the initial condition and so the reduction in total re-equilibrium time may not be as great as it would appear.