Chromatography Forum

Dear all!

We have to measure BTEX, THM, trichloroethylene etc. and 2-butoxyethanol from air. We have a Markes TD-100 7890-7000C GC-MS system. We tried out Tenax and Carbograph/Carboxen/Tenax trap with Tenax and graphitised carbon cold traps. The TD method was: 6 min desorb time (300 °C), the cold trap: -20°C then 320 °C with 3 min hold time. The used column was PONA. The TD is directly connected to the column.

We have only problem 2-butoxyethanol it gives a broading peak about 0,5-0,7 min wide peak. The other compounds gives really nice peaks, we tried out even free phenols and with a little tailing but they give really nice peaks. We tried to leave out TD from the system and directly inject to the column with an SL inhlet and it was really good without TD.

Thank u for any helps!
Erdno

We have only problem 2-butoxyethanol it gives a broading peak about 0,5-0,7 min wide peak.

Catalytic thermodegradation? Are you use inert tubes (specially deactivated) for TD?

Dear Sav!

We are using inert tubes and caps and the flow path should be inert too (as i know). I tried to decrease the temperature (120°C for flow path and 200 °C for desorption temp) but it didnt use too.

Erdno

I presume you're using a 5-phase column. Please correct me if that is not the case. Butyl cellosolve tails pretty badly on my 5-phases. Perhaps you could go to a wax or a cyano phase and get better chromatography.

I presume you're using a 5-phase column. Please correct me if that is not the case. Butyl cellosolve tails pretty badly on my 5-phases. Perhaps you could go to a wax or a cyano phase and get better chromatography.

Seems it is not a problem of inappropriate column since he wrote:
"We tried to leave out TD from the system and directly inject to the column with an SL inhlet and it was really good without TD."

Split or splitless?

Our TD is directly connected to do column with an union, so no split on inlet. At TD after the cold trap we use 20:1 split (tried out 80:1 split too).

Erdno

What if you use Tenax only in the cold trap?

Or the carbon only?

The 2-butoxyethanol may be adsorbing too strongly in the cold trapping material. At -20C can you trap these analytes on something inert like just glass beads or the walls of the trap itself?

Dear James!

I tried out Tenax cold trap and carbon cold trap too. Both of them was same. I dont have any empty trap to try out if i can trap them on wall (or glass beads).

Erdno

the flow path should be inert too (as i know).

Try to replace transfer line (if you can). I don't think that its desorption issue since phenols are ok.