Running 5973 "standard" source at high temp

Discussions about GC-MS, LC-MS, LC-FTIR, and other "coupled" analytical techniques.

7 posts Page 1 of 1
Hi all,

I've seen lots of suggestions to run the source at high temp (280 C or so) to reduce tailing in high boiling PAHs. As far as I know our 5973 has the "standard" source rather than the inert, and the default max is set at 250 C. Furthermore Agilent's official documents suggest the range is up to 250 C. Will it damage the source to run it at 280 C? I spoke with a chemist at Restek who believed it wouldn't be a problem.

Thanks in advance
I think it shouldn't be a problem. Don't expect a lot less tailing by going from 250°C to 280°C, though.
Tailing is more about how dirty the source is than just the source temperature. A higher temperature will help keep it clean longer, but unless you can bake it at 300c or higher it will eventually get dirty and begin to tail for PAH analytes.

Another trick that will work is to run hydrogen carrier if you can do it and keep the sensitivity needed. If not you can install a simple three way valve so that when you are not running samples you can switch to hydrogen carrier and keep the source and column temp elevated and it will work to clean the system. The 5973s is compatible with hydrogen, but only some 5975s are, you have to check the magnets on the source to be sure on those. I currently run my 7000C with hydrogen and have little or not tailing and the source stays much cleaner. Tuning for DFTPP is possible but may require a little tweaking if you run hydrogen as the carrier for analysis, but I have yet to get it to pass consistently for BFB tuning for volatiles.
The past is there to guide us into the future, not to dwell in.
Try installing a 6mm drawout plate in place of the 3mm. This should improve heavy PAH tailing and resolution. It's worked well for us on a number of instruments.

Thanks all for the replies. Our lab director is averse to running hydrogen, so unfortunately that's out. Restek did recommend the 6mm drawout plate in addition to a higher source temp. However, the instrument is still under warranty and they warned me that they wouldn't repair a source that was damaged by running too hot. I'll give the larger plate a shot.
cjm wrote:
Try installing a 6mm drawout plate in place of the 3mm. This should improve heavy PAH tailing and resolution. It's worked well for us on a number of instruments.

It might be common knowledge but I was not aware of this. After googling it seems you have a good point. Interesting post!

Is there a similar option for the EI extractor ion source on a 7000c?
To the OP: what are your chromatographic conditions? Column, oven ramp, flow, etc. There may be some changes we could make to your settings to improve the chromatography.

As for the 7000c, I'm not familiar with it. An interesting effect (that I still need to verify 100%) when switching from the 3mm to the 6mm drawout plate, is the repeller apexes of 69/219/502 when ramping all shifted to the right. On two instruments it's shifted far enough that we're running the repeller in the high 30s. It's not a problem, it's just different.

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