Thermo GC-MS/MS

[yangz00g]

Any one has experince with Thermo's Trace GC Ultra-TSQ MS/MS? We had one installed recently, but is experiencing some high N2 signal (comparing to H2O signal, H2O/N2 ~2:1.2 to 1.3) during the turing process. The vacaum is very good. Anyone sense there my be a leaking? Thanks in advance.

[Ron]

What is the ratio of nitrogen to oxygen? If it about 4 to 1 you have an air leak. I suspect the ratio will be much larger, around 50 or 100 to1.

Do you have one of the Valco traps on the carrier in line? These often release a large quantity of nitrogen when first installed, and this lasts for a long time if the trap in not mounted vertically. If you have one of these traps try running at a 250:1 split for 20 minutes and see if the nitrogen goes down.

[yangz00g]

Thank you very much, Ron.

The N:O ratio is around 3:1 consistently. There is a N-pretreated filter in line, but have it purged for quite a while.

The mystery is when it's operated at 1ml/min, N signal is at normal range, but when flow rate is increased to 2, N become abnormal. We have a thermo technican here struggling. The answer is likely to be "no problem".