Strange early peaks - Scion SQ

[crosemeyer]

Hi all.

I'm working on setting up a new Bruker Scion SQ, the intent is to analyze very pure gases for total organic compounts at a sub-ppt level. We're using a Valcor cold trap.

Currently just kind of playing with the instrument to get a feel for the software and instrument.

Cold trap at -180C for 3.35 min, then raise PTV to 200C at 150C/min
Oven holds at 50C for 7min, then ramps to 280C (Column is CP-SIL 5CB 30mx0.32 DF=1.0)

Right now, I've just been running either N2 or He through the trap, and I'm getting, to me some very strange behavior. With N2, I'm getting a "dip" (looks similar to a flat water dip in some IC applications!) at ~7-->7.4 min, followed by a peak (identified as 1,1,1,2,2,3,3-heptafluoro-3-methoxypropane) around 7.6 min. With He, I get two peaks (7.3 and 7.6) identified as the same (roughly same TIC as N2 program). He is the carrier.

Any ideas?

[Peter Apps]

If you are learning the instrument then you need to be running samples whose composition you know - then you can tell whether the hardware and the operator are working properly. When you are sure that everything is running smoothly is the time to be running unknowns.

Peter

[crosemeyer]

Hi Peter.

Yes, as I said, I'm kinda just playing now. I've never analyzed gases in this way, and I'm wondering if these are some kind of "solvent peak". The gases I'm running through the cold trap are just my carrier and purge; both should be pure.