Chromatography Forum

Hi All,
I'm running into another issue with my PE Turbomatrix 650. I can't seem to get any desorption of the heavier compunds. I'm running this program from the ATD onto an HP 5890/5972.

Room temp dry purge for 6.0 minutes at 50 mL/min
desob1 (onto cold trap) 330 C 6 minutes at 40 mL/min
desob2 (onto column) trap heat from -20->325 99C/sec
1.2 mL/minute onto column flow 6 min desorb

i'm using the PE Air toxics trap and tubes. we're running EPA method TO-17, at least trying to.

Now here is the weird part. the 650 has the Internal standard injection option, which we use, i can get recoveries of IS up to 18 minutes into the 27 minute run but my analytes that were spiked onto the tube prior to loading stop around 12 minutes. We also have a purge and trap GC/MS set up so i ran the spike standard there and everything recovered perfectly. the concentration of spike doesn't seem to matter either, i have loaded the tubes at 400 ng/l and get identical results, as far which compounds recover, to the 50 ng/L spike. I've tried liquid spiking the tubes and gas phase spiking. at one point i jumped the stage 1 desorb, onto trap, flow rate to 70 mL/min all to no avail. I'm at Wits End, any input is appreciated.

A couple questions:
What sorbents are in the PE air toxics trap?
What range of compounds are you seeing and not seeing?
Are you going splitless both from the tube and the trap?

For heavier compounds on a strong sorbent it can be difficult to get them desorbed with a splitless flow of 1.2mL/min. I use a rule of thumb of at least 10-15mL/min for trap desorb giving a trap desorb split ratio of about 7:1. Can you try a higher column pressure? I routinely run 3.0mL/min column flows to a turbo equipped 5975 to increase mass on column while still keeping the desorb flow through the trap between 10 and 15mL/min for more sensitive methods. Peak shape looks great for heavier compounds, not so great for lights. If you're running a diff pump, you're outa luck on higher flows.
Tube and trap heating times of greater than 5 minutes are more than enough. For the PE turbomatix's, the trap is heated instantly and the tube heats to 275 in less than 45 seconds. This was confirmed with a thermal imager.

A couple questions:
What sorbents are in the PE air toxics trap?
What range of compounds are you seeing and not seeing?
Are you going splitless both from the tube and the trap?

As for the PE traps all i could find is "carboneous sorbents" and little else.

I can recover with reliability halo-methanes and alkanes as well as ethers and benzene. anything that elutes after benzene is pretty hit and miss.

I was running a split from the trap using recollect mode on the turbomatrix 650.

Since the last post i have reworked the method with your suggestions and it did not respond any better. I also used the settings in PE method paper here

https://www.perkinelmer.com/lab-solutio ... 909_01.pdf

Which also didn't help. Looking back through the records there was a point where the old settings worked fine but when i went restart the method something happened and now i'm getting the anomalous recoveries. I have done some work in cleaning out the rotor in the main valve and changing traps and transfer lines inside the turbomatrix to no avail. At this point I'm a bit lost having no experience at all with the TD introduction method.