Contamination on GC-FID

Hello GCarmen , use the Condensation test to determine if the issue comes from the gas supply or the inlet: Using the Condensation Test to Troubleshoot the GC Inlet - Agilent Technologies - GC Articles - Gas Chromatography Portal - Agilent Community. 

A quick way to run a blank is just to remove the syringe from the autosampler.

As Mayumi Fukuda has mentioned, one of the possibilities is contamination in the split vent line. It may be caused by overloading the the liner. What injection volume and inlet conditions are you using? (specifically inlet temperature, pressure and liner part number?). 

hello Carlos Vargas  and Mayumi Fukuda 

Thanks for your ideas!

so, simplest thing i could do from all of your ideas, is an blank run without syringe. I did that and the chromatogramm looks clean. So i assume, that my contamination comes from outside the system. Before i am going to the effort to clean split vent trap and so on...

If i had a contamination in the vent trap or the line, then i must have it in the blank run as well, right?

Carlos Vargas said:

As Mayumi Fukuda has mentioned, one of the possibilities is contamination in the split vent line. It may be caused by overloading the the liner. What injection volume and inlet conditions are you using? (specifically inlet temperature, pressure and liner part number?

We use same liner, injection volume and conditions since 4 years (routine analytics) and we never had this problems. Overloading should not be a problem as well, because we use the same concentration since years.

Hi!

Try to bake out your column and condition it. 

Try to reverse your column, install the injection side to detector side. Sometimes column will shoot stationary phase to the detector, because of sample and age of column.

What is your configuration. Is this only column installed in-between evaporator and detector, or is there any switching valves installed?  

Hi!

Try to bake out your column and condition it. 

Try to reverse your column, install the injection side to detector side. Sometimes column will shoot stationary phase to the detector, because of sample and age of column.

What is your configuration. Is this only column installed in-between evaporator and detector, or is there any switching valves installed?  

Hi Beka

We solved the problem. At the end, we just replaced the column. After baking out, cleaning the column and cutting it.
But yes, it was the only column installed and no switching valves.

I just wonder, why we could not see that on the blank run, any idea?

Thanks and KR, GCarmen

Hi Carmen,

Visually check your column in signs of contamination of stationary phase. It looks like your column was too old. In that case you could just reverse the column direction, and put for for long term conditioning at room temperature, then condition it at maximum temperature with desired flow for efficient analysis, then try to run with sample. Contamination of stationary phase at the end of column could break your peaks and shoot it as peak, or stationary phase could carryover with peak! If this column worked for many years usually nothing helps instead of changing to new column. Also, depends on your detector. FID should be cleaned at least once in a 6 month, what is the ceramic isolators condition, is there any electrical noises caused from electrometer, analog board all things need to be checked, sometimes just rebooting your instrument and PC could solve the problem. Your instrument has very simple configuration, so that is thy the solution should be very simple.