Chromatography Forum

Dear all,

my student misunderstood one of my explanations and opened the vent valve of our Agilent 7000B MSD during the vent cycle, maybe around 10 min after I had started it.

I have to assume the quads were still about 130 °C and the source was maybe 140-ish °C (all well above the 100 °C recommended). Since the foreline pump was still running, air was sucked in for 10, 15 or 20 min. The turbo pump should have been off or at a low rpm.

Has anyone else been through this before? If so, how much of a damage has it caused in your case?

Once I have put the system into operation again, I would compare tune reports before/after. Any additional suggestions?

Thanks and best
cb23

One thing I might be concerned about is whether or not oil from the rough pump made it into to the MSD. If it's not visibly obvious that this happened you still might be dealing with major hydrocarbon interference when you start back up. But there might be other things to check before a restart in a case like this.

If the rough pump was still running then it shouldn't have back streamed any oil, the flow on those are quite high and shouldn't allow the oil vapor to flow back to the analyzer, plus the turbo would be a restriction to also help prevent that.

Since it was cooling, it shouldn't oxidize the source any worse than a small air leak would over a long period of time at high temperature. A good source cleaning should remove that if it is present. The quads are gold and fused silica so a little air won't damage those when they are warm.

As long as you are not scanning when that occurs all should be good to go. If it was scanning you would need to worry that the filaments were burned or possibly damage to the electron multiplier with it being hit with high pressure when energized. But since it was already venting those were both turned off.

Now if the student had vented at the vacuum pump fitting, then you would possibly have problems. Damage to the turbo is possible when that happens and if it is an oil diffusion pump model, then you will definitely be cleaning oil from the analyzer if vented from the wrong end of the vacuum path.