Varying MTBE responses using Purge and Trap

Chromatography Forum: GC Archives: Varying MTBE responses using Purge and Trap
Top of pagePrevious messageNext messageBottom of pageLink to this message  By michael dunn (host-209-214-119-128.bna.bellsouth.net - 209.214.119.128) on Monday, July 19, 1999 - 06:00 pm:

I lose MTBE response over a few days. Sometimes stable then declines. New traps help for awhile. Using BTEX traps and carbopack b & c. Also limited upper range about .1 ug/l then flattens out. I have Tekmar 2000 and 3000's. Purge at 38-42 ml/min. for 11 min. Desorb per manufacturer. Any suggestions?


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Jay Gandhi ( - 161.16.1.48) on Thursday, July 29, 1999 - 11:24 am:

Have you tried isolating purge-trap by directly injecting into GC?
Oxygenates in general is very sensitive to active sites, specially exposure to hot metal surfaces(injector, valves etc..) This effect is magnified at low level trace analysis. You may have to do extensive trouble shooting on this one.
Any questions, plese e-mail me.
Thanks.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Jay Gandhi ( - 161.16.1.48) on Thursday, July 29, 1999 - 11:25 am:

 By Jay Gandhi ( - 161.16.1.48) on Thursday, July 29, 1999 - 11:24 am:

Have you tried isolating purge-trap by directly injecting into GC?
Oxygenates in general is very sensitive to active sites, specially exposure to hot metal surfaces(injector, valves etc..) This effect is magnified at low level trace analysis. You may have to do extensive trouble shooting on this one.
Any questions, plese e-mail me.
Thanks.


Top of pagePrevious messageNext messageBottom of pageLink to this message  By Dan Vassilaros on Tuesday, August 3, 1999 - 08:11 am:

Sounds like more of a trap problem than adsorption by the Tekmar plumbing. The 2000 and 3000 use stainless steel traps, and perhaps the trap tubing surface becomes slightly more active with temperature cycling. Are glass or deactivated ss traps available, coated with Silcosteel or thin-film siloxane? I use Silcosteel-coated stainless steel liners in one of my thermal desorption applications. They are sufficiently inert for the most adsorptive target analytes. (I do not do oxygenate analysis.) I had to discontinue using my 3000 because the target analytes were more-or-less permanently adsorbed by the plumbing.


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