Page 1 of 1
Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Thu Aug 18, 2016 5:23 pm
by djones86
We are running volatiles on A Varian 3900 with a saturn 2100D with a 72 compound standard and are loosing the first 30 or so compounds. We are running the GC at 35c for 2 min, 4 c/min to 50c, then 10 c/min to 220c holding for 12 minutes with a split of 100. The purger is a tekmar 3000 with a 25 ml sparge tube it is purging for 11 minutes at 40 ml/min, desorbing for 2 minutes at 250c, with the transfer line at 110c and the valve at 110c.
The mass spec passes tune with BFB and the peaks roughly after benzene can be seen with relative ease but almost everything before is showing as nothing but noise. It is this way whether the injection is made with the purge or direct inject. I am unsure what needs to be done to fix this issue but anyone who could lend information would be greatly appreciated.
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Mon Aug 22, 2016 7:22 am
by Hornet
What's the Ion trap temperature?
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Mon Aug 22, 2016 7:29 am
by tkubowicz
Hello
Have you checked analytical trap in Tekmar? Are you sure it is ok? (perhaps it is saturated or needs to be bake out).
Regards
Tomasz Kubowicz
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Mon Aug 22, 2016 12:09 pm
by djones86
The Ion trap temperature is sitting at 150 and the tekmar trap bakes for 15 minutes after every purge but it is possible that it could need a longer bake. Thanks for the responses
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Tue Aug 23, 2016 3:38 am
by VOAnalyst
When was the trap last changed? Have you been able to see the early peaks in the past?
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Tue Aug 23, 2016 12:32 pm
by dblux_
... It is this way whether the injection is made with the purge or direct inject...
Begin diagnosing with isolating the problem to GC/MS or P&T.
Seems that it is GC/MS related.
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Tue Aug 23, 2016 2:06 pm
by Steve Reimer
Have you looked for a leak that seals up when the oven temperature rises? Could be at the inlet, or even a cracked column. An air and water check at cold oven and then again with a hot oven would diagnose.
Re: Loss of early retention Peaks on Varian 3900/2100d GC-MS
Posted: Wed Aug 24, 2016 12:33 pm
by djones86
VOAnalyst:
The P&T trap was changed earlier this year in February and yes we have been able to in the past
dblux_:
I tend to think loss of peaks is in the GC/MS, the P&T i dont think is working properly due to mass loss between direct and P&T at higher retention.
Mr. Reimer:
Running an air water check at starting levels of column temp 35c show ok on both air and water. the higher temps drop the percentages lower