My latest adventures in instrumentation and method development ...
Some GC/MS problems are straightforward.
This one has turned into a full-blown detective story.
I’m still chasing an intermittent HIGH VACUUM error occurring mid-run on an Agilent 5977B diffusion pump system.
So far, the troubleshooting adventure has included:
~ Diffusion pump replacement
~ Diffusion pump heater replacement
~ Diffusion pump temperature sensor replacement
~ Vacuum gauge replacement
~ Main board replacement
~ AC board replacement
~ Software upgrade to a newer MassHunter version
…and somehow the exact same intermittent high vacuum fault still appears in the middle of runs.
The fun part about intermittent failures is that the instrument can behave perfectly long enough to make you think you solved it… right before reminding you that you absolutely did not.
To be fair, Agilent tech support has been very helpful overall (seriously appreciated), although troubleshooting sessions occasionally take unexpected turns.
For example:
I learned it is apparently possible to spend 15 minutes discussing “burping” vacuum hose.
...
How many GC/MS analysts print an autotune report, file it away, and never look at the numbers?
- EM Voltage = 1187 V
Typical guideline:
• 800–1200 V = Excellent
• 1200–1800 V = Good
• 1800–2200 V = Aging
• >2500 V = Near replacement
- Water = 2.2%
Typical guideline:
• <5% = Excellent
• 5–20% = Normal
• >30% = Investigate
Often decreases significantly after overnight stabilization.
- Nitrogen = 0.5%
- Oxygen = 0.2%
Typical guideline:
• N₂ <5%
• O₂ <2%
Elevated values can indicate air leaks.
- Relative Abundance 219 = 74.2%
....