Chromatography Forum

I work at a Biodiesel plant and recently our GC has been causing some headache. It doesn't appear to be picking up certain peaks in the right quantity. All of the areas are reading much lower then they actually are. The column has not been changed recently, nor has it been calibrated since these problems started occuring. My question is, how do I know when the column needs to be changed/adjusted? and whether or not this sounds like it is the problem. We have run over 1000 samples on this column, we use an FID detector. Anyways, please bear with me and help me out, if something doesn't sound like it makes sense please ask.

We have an Agilent 7890A GC with a 7683B auto injector, we use Chemstation.

Thanks,
Ryan

We need some information.

Did this happen all at once or have the values decreased gradually?

Do you run calibration standards regularly and have they been giving the correct results?

How often do you change your septum. inlet liner, and gold seal?

I recently learned at a GC class that most problems occur in the inlet and that it is rarely the column although columns do age and can be destroyed by poor GC practices.

All of the areas are reading much lower then they actually are.

Are the peaks smaller also? Please clarify.

ryanegger,

Assuming you are doing triglycerides, 1000 injections for the oven profile you have to use is quite a lot. It is highly likely that your column is shot.
This would be evident as tailing peaks, missing peaks, poor retention time reproducibility, etc....

The other question that comes to mind is when you folks last did inlet maintenance. As a starting point in troubleshooting, I would change perform inlet maintenance on this instrument and I would order a spare column.

Best regards.

Yes, we are running triglycerides. Also their is peak tailing. I will change the inlet liner and evaluate, but I think you are right, the column is likely shot. Thanks for the symptoms of the column crash! I will let you know if it works out.

Thanks again,
Ryan