Loss of early retention Peaks on Varian 3900/2100d GC-MS

[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.

[Hornet]

What's the Ion trap temperature?

[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

[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

[VOAnalyst]

When was the trap last changed? Have you been able to see the early peaks in the past?

[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.

[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.

[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