Chromatography Forum

Hi there,
I am using my CP WAX 57CB column for a GC-FID with a 1.2 ml/min flow rate (He) and the pursue is very high 134 kPa. I removed the column and cut 1cm and connected the pressure was still high. The FID got to 2000 pA (did a blank injection).
I really appreciate if you help me to solve this issue.
Thanks in advance.

Hi there,
I am using my CP WAX 57CB column for a GC-FID with a 1.2 ml/min flow rate (He) and the pursue is very high 134 kPa. I removed the column and cut 1cm and connected the pressure was still high. The FID got to 2000 pA (did a blank injection).
I really appreciate if you help me to solve this issue.
Thanks in advance.

Think of a column as a restrictor. Column ID and lenght is more important than type of a column.
Check if your column isn't clogged and whether it is properly installed.
What were the circumstances you noticed high pressure ?
Any maintinence works on inlet, column or detector.
What was the pressure earlier, before you noticed 134 kPa.
Is it configured properly in GC ?

Hey, that's first time I'm using this column so no information on previous pressure. I usually get 45 kPa on my TG-5 column (30mx 0.25x0.25) and thought 134 kPa is too high! However as I checked the pressure can go as high as 400kPa for a 50m column with 0.25 mm ID, but I still think 134kpa at 35C is too high!
I check the column connection and reconnected it. maybe my conditioning was not enough?

Hey, that's first time I'm using this column so no information on previous pressure. I usually get 45 kPa on my TG-5 column (30mx 0.25x0.25) and thought 134 kPa is too high! However as I checked the pressure can go as high as 400kPa for a 50m column with 0.25 mm ID, but I still think 134kpa at 35C is too high!
I check the column connection and reconnected it. maybe my conditioning was not enough?

Hi. Conditioning influences baseline not pressure.
Check with: https://ez.restek.com/ezgc-mtfc what pressure should you get for your flows and temperatures. Isn't your column clogged with rests of rubber cap in the column ?

When trimming a column, take a chunk if you suspect that the end is clogged or dirty. The only reason to score and knock off 1CM is if you made a ragged cut when removing the previous 7-10CM.
134kpa sounds reasonable for a 60M column given your 30M column pressure.

If you double the column length you will more than double the pressure. Just a thought.

Thanks @dblux_ for sharing the Link. It is vey handy and makes life easier!
Thanks @DR I will cut 7cm.
Thanks @James, I have benefited from all your responses in GC related posts.

Looks like 110kPa is a normal pressure at 35C for a 50m column.