by
LALman » Sat Apr 28, 2018 6:03 am
Its a 6890N, I swapped in a known good EPC and the problem of variable IS and Surrogate recoveries persists. Although, oddly, I necessarily had to R&R the inlet while changing out the EPC. For some reason, the intensities of all peaks are 50% of what I had, across the board. So, now I can rule out the EPC for variability. Maybe the column position in the inlet is that critical? I was careful to cool the inlet and transfer line before shutting down the GC for the changeover. And I capped the column. I'm pretty sure I did not oxidize my 5973 MS source.
I think now, that its got to be a flow problem in the Archon or the Tekmar. I ran a couple samples using the Tekmar 3000 glassware. The signals were higher 90% of normal. So provisionally, I think its a problem with flows from the Archon autosampler running in soil mode. I removed and cleaned the needle assembly so I can now rule that out. Tomorrow, I will try cleaning the transfer line and check to see if the in-line gas filters might have been compromised and have too high back pressure. Boy do I wish I had a digital flow meter.