5975 Tune Problem solved...but how?
Posted: Fri Nov 09, 2012 3:51 pm
Hi all..
I'm running a 5975C/7890A and have been struggling with a serious tune problem, which I just fixed, but don't know how I fixed it. I had run some pretty awful sediment sample extracts a few weeks ago. The MS source at the time was already close to needing a cleaning, filament 1 was toast. So after I ran these samples I took the source apart, cleaned as normal, clipped my column, did routine inlet maintenance. First, here's my targets when tuning. I had a DFTPP target tune run back a while ago and I just keep the following steady and it has proven very successful in passing a DFTPP tune. Entrance lens offset = variable to fine tune each ion.
Peak widths for 69/219/502 = 0.50 amu
target abundance for 69 = 1.5 million counts
relative abundance for 131/219/414/502 = 40%/40%/1.9%/1.0%
After everything was back to temperature for a full day I went in to manual tune. Usually when I turned the MS on my percentages were pretty close, within 20% of my target, and I would just do minor adjustments to the entrance lens offset voltages, maybe turn up or down the EM a click or two. This day was not the case. 502 was down at 0.4%, 131 was at 75% so I had to to pretty major tweaks to get everything where it should have been. Then I ran a DFTPP standard. Ion 51 was more than 80% of 198. It usually runs around 45% for this system. Ion 197 was an issue as well, going well over 1% necessary for one of my methods. The system was suddenly extremely low-end-sensitive.
I assumed source contamination. So I re-cleaned everything, put everything back together....same thing. Yesterday I took it apart again, noticed repeller ceramics had some discoloration so I (very skeptically) took Agilent's advice and used a cotton swab and methanol to clean it. Also I used their advice for source parts solvent sonication: Water->Methanol->Acetone->Hexane. Put everything back together, went to manual tune, and now everything was crazy again, 502 was 7%!! 414 was 5%...so I tweaked everything to how I normally do to get the ratios I'm after. Ran a DFTPP standard. It's perfect.
So my question is: what did I do the THIRD time that made all the difference? Could it have been the ceramics? Could it be the solvent cleaning? Something else? Thank you for any thoughts on this. This is the first time I've had any real trouble with this instrument and I'm not great at troubleshooting this MS yet.
I'm running a 5975C/7890A and have been struggling with a serious tune problem, which I just fixed, but don't know how I fixed it. I had run some pretty awful sediment sample extracts a few weeks ago. The MS source at the time was already close to needing a cleaning, filament 1 was toast. So after I ran these samples I took the source apart, cleaned as normal, clipped my column, did routine inlet maintenance. First, here's my targets when tuning. I had a DFTPP target tune run back a while ago and I just keep the following steady and it has proven very successful in passing a DFTPP tune. Entrance lens offset = variable to fine tune each ion.
Peak widths for 69/219/502 = 0.50 amu
target abundance for 69 = 1.5 million counts
relative abundance for 131/219/414/502 = 40%/40%/1.9%/1.0%
After everything was back to temperature for a full day I went in to manual tune. Usually when I turned the MS on my percentages were pretty close, within 20% of my target, and I would just do minor adjustments to the entrance lens offset voltages, maybe turn up or down the EM a click or two. This day was not the case. 502 was down at 0.4%, 131 was at 75% so I had to to pretty major tweaks to get everything where it should have been. Then I ran a DFTPP standard. Ion 51 was more than 80% of 198. It usually runs around 45% for this system. Ion 197 was an issue as well, going well over 1% necessary for one of my methods. The system was suddenly extremely low-end-sensitive.
I assumed source contamination. So I re-cleaned everything, put everything back together....same thing. Yesterday I took it apart again, noticed repeller ceramics had some discoloration so I (very skeptically) took Agilent's advice and used a cotton swab and methanol to clean it. Also I used their advice for source parts solvent sonication: Water->Methanol->Acetone->Hexane. Put everything back together, went to manual tune, and now everything was crazy again, 502 was 7%!! 414 was 5%...so I tweaked everything to how I normally do to get the ratios I'm after. Ran a DFTPP standard. It's perfect.
So my question is: what did I do the THIRD time that made all the difference? Could it have been the ceramics? Could it be the solvent cleaning? Something else? Thank you for any thoughts on this. This is the first time I've had any real trouble with this instrument and I'm not great at troubleshooting this MS yet.