Chromatography Forum

Hello,

I've problem with new Entech 7200A. Some oxygenated VOCs are missing from the chromatogram.

I tried all possible options for method setting including switched back to running as 7200 but still can get ketone and ester peaks back. Please let me know if you ever had missing VOCs peaks from switching Entech 7200 to 7200A. I've been working with the previous model 7200 for over 10 years. The system worked fine but we need to replace the obsolute GC so we get a new system.

Any suggestion on solving the problem is highly appreciated.

Cheers

Sounds like an active site. I've seen water solubles and heavy bois drop out before, oxy compounds is a new one. Set M1 to 80 C and try an injection, bake out the hydrocarbon trap overnight or replacing the transfer line are where I would start.

70 eV wrote:
Sounds like an active site. I've seen water solubles and heavy bois drop out before, oxy compounds is a new one. Set M1 to 80 C and try an injection, bake out the hydrocarbon trap overnight or replacing the transfer line are where I would start.

Thank you for your reply. Transferline is already replaced. M1 dehydration is at 80C. Still cannot find missing peaks. We have NAAQS for 1,4-Dioxane which can be detected with our old 7200. We've new system installed since April 2022, trying to get lower LOD but it didn't work and peaks're still missing.

Are you missing low points or the compound entirely? If they're totally gone I'd start spiking individual analytes into cans, otherwise jack the multiplier voltage and see if your top end is still linear.

Have you already gone up and down the system with the leak detector and ran a leak check off the 7200 blind port?