Special Topics
Performing cool on-column injection onto 250-µm and 320-µm columns
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the size of the column and syringe needle you will use. (See the previous
section to identify the correct insert.)
Use the following steps to remove an incorrect insert and to install a new one:
1. Lower the temperature of the GC oven. After the oven is cool, turn the
oven off, and set the inlet pressure to 0.
2. Remove the column along with its column nut and ferrule.
3. On top of the oven, unscrew and remove the inlet septum nut.
4. Replace the old septum with the new through-hole septum, and set the
septum nut aside.
5. Remove the spring from the inlet, and set it aside. Be careful not to lose or
damage it because you will use the spring with the new insert.
6. Remove the existing insert from the inlet by pushing it out from below
with a piece of column. Store the insert for possible later use.
7. Drop the new insert straight into the inlet from the top. The end of the
insert in which you inserted the needle should be up; the end of the insert
in which you inserted the column should be down (see the previous
section on checking the needle-to-column size). Use the identification
rings to help you remember which way to install the insert.
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