Chromatography Forum

Hi,

I really hope for some help regarding my problem. I use a 100m column with a temperature programme from 50 C to 230 C on a GCMS. The analytes I am measuring are eluting from 20 min (GC temp around 160 C) to 55 min. As an analyte that elutes at 50 min is at a low concentration I am having a problem as the LOD is a bit too high, it is a broad peak so I think the S/N could be corrected with a better GC method. I currently use constant pressure and so the flow gets lower at the time the last analyte elutes (50 min, GC column temp 230 C). I think I could improve the LOD with changing the method to a constant flow, except I do not know the best way to change the method as the method translator programs I found so far do not have this option. It took me some time to develop an adequate separation and I do now want to go through all the work again if it is not neccesary.

I kindly ask for any suggestions and comments!

Kind regards

Welcome to the forum.

With no information on the GC you are using or the diameter of the column, the only advice anyone can give is to enter the column dimensions in the GC control software and tell it the linear flow you want (35 cm/s for helium, 50 cm/s for hydrogen) and let the electronics do the work.

Peter

Hi and. I agree with Peter. To get help, you need to provide more info. It might be possible to improve LOD by translating a method to constant flow or without it.
What is your column internal diameter?
What is the carrier gas?
What is the column gauge pressure (or initial flow rate, or initial hold-up time)?
What is the temperature program?
What is the width of the low S/N peak?
lmb