Chromatography Forum

Hi,
I am using a pora plot u column and a molsieve to measure permanent gases and c1, c2 gases. I have to isolate the molsieve when co2 and c2 gases come out.
I am using a six port valve to isolate the molsieve column.
when isolating the molsieve the plot coloum is connected to the detector through a adjustable restrictor.
Can someone please tell me how to adjust this restrictor to apply same back pressure as the molsieve column

Thanks a lot

Setting up the needle valve will depend on how the flow through the columns is controlled, flow control or pressure control.

For flow control proceed as follows.

1. Allow the columns to equilibrate at the temperature you will be using them at .
2. Make sure that you have carrier gas flowing through both columns by switching the isolation valve for the mol sieve column to the correct position.
3. Monitor the head pressure to the columns and when it is steady make a note of the pressure.
4. Switch the isolation valve so that mol sieve column is isolated.
5. Now adjust the needle valve to give you the same head pressure that you noted.

For pressure control

1. Allow the columns to equilibrate at the temperature you will be using them at .
2. Make sure that you have carrier gas flowing through both columns by switching the isolation valve for the mol sieve column to the correct position.
3. Measure the flow coming out of the two columns at the exit of the detector, making sure that you have any detector flows turned off.
4. Switch the isolation valve so that mol sieve column is isolated
5. Adjust the needle valve to give you the same flow at the detector outlet.

Gasman