what is the appropriate shut down method for GCMS

[jiangds06]

Need to standby over weekend. what it the gc/ms shut down method? Carrier gas reduced to 0.5ml/min? Inlet temperature 150C, split mode 20:1 oven 150C, transfer line temp 250C, MS QUAD and source 150C and 230C? Anything that I need to change?

[James_Ball]

Need to standby over weekend. what it the gc/ms shut down method? Carrier gas reduced to 0.5ml/min? Inlet temperature 150C, split mode 20:1 oven 150C, transfer line temp 250C, MS QUAD and source 150C and 230C? Anything that I need to change?

Over a weekend we don't change anything except keep the oven at least 150c instead of the normal starting temp of around 50c. That will help prevent any hydrocarbons that might be present from accumulating on the column phase. You may lower the split if you are worried about using too much helium, or even plumb in a nitrogen source if really worried about wasting helium, but we just count it as an operating expense. Quad and source temps can remain at running levels, it doesn't take that much more electricity to keep them heated, and you don't have to wait for them to come back to temp on Monday to start analysis.

The old HP5970 had a setting to reduce the turbo pump down to 80% speed as a standby, but keeping them at 100% seemed to make them last longer.

Unless you are shutting down for several months I really don't see any advantage to changing anything over what you would for an overnight pause in analysis.

[jiangds06]

Thank you so much!

Need to standby over weekend. what it the gc/ms shut down method? Carrier gas reduced to 0.5ml/min? Inlet temperature 150C, split mode 20:1 oven 150C, transfer line temp 250C, MS QUAD and source 150C and 230C? Anything that I need to change?

Over a weekend we don't change anything except keep the oven at least 150c instead of the normal starting temp of around 50c. That will help prevent any hydrocarbons that might be present from accumulating on the column phase. You may lower the split if you are worried about using too much helium, or even plumb in a nitrogen source if really worried about wasting helium, but we just count it as an operating expense. Quad and source temps can remain at running levels, it doesn't take that much more electricity to keep them heated, and you don't have to wait for them to come back to temp on Monday to start analysis.

The old HP5970 had a setting to reduce the turbo pump down to 80% speed as a standby, but keeping them at 100% seemed to make them last longer.

Unless you are shutting down for several months I really don't see any advantage to changing anything over what you would for an overnight pause in analysis.