Chromatography Forum

Hello to everyone! I have come up with a tricky task! I am using an SRI 8610C GC system with ECD/FID in a raw and running workplaces atmosphere BTEX samples. The problem is that ALL BTEX peaks are reduced sudenly. One day I make a quality control (QC) 10ppm standard and all its ok,the next day the same standard is ok BUT the 3rd day the same standard is calculated 7 ppm!!! I made new 10ppm standard but again it was measured 6.5-7 ppm!!! Is there a leakage in my system? The liner is already cleaned, the bolts are tightened and the syringe (manual injection) I checked is ok. I have also changed the septum! 30% loss during 3 days??? Is it an FID problem? The column also is brand new, about 2 months old...Any ideas?
Thank you very much
John

I would definitely check that the flame tip of the FID isn't partially blocked.
Removing this and giving it a quick flush with acetone and using a thin piece of wire should clear the debris.

Re-test your sample to see if there is improved sensitivity.

Good Luck!

I re-check the sample after weekend and it is OK!!!! But I will give a clean in the FID wire and collector electrode.....