perkin elmer TD-GC-MS

[yyaann]

Hi everyone,
I am working with a Perkin Elmer TD-GC-MS, however, I found the N2 and O2 levels are relatively high in the system, when the column flow (He) is 1ml/min, the N2/He is about 30% and O2/He is around 10%; when the column flow is set to 1.5ml/min, N2/He is about 12% and O2/He is around 5%. The water level looks okay in both cases. The GC is connected to ATD 650 and the outlet split is off when I check the air/water. Is it normal for this system?
I appreciate any suggestions.
Thank you very much!

[wss]

Hi everyone,
I am working with a Perkin Elmer TD-GC-MS, however, I found the N2 and O2 levels are relatively high in the system, when the column flow (He) is 1ml/min, the N2/He is about 30% and O2/He is around 10%; when the column flow is set to 1.5ml/min, N2/He is about 12% and O2/He is around 5%. The water level looks okay in both cases. The GC is connected to ATD 650 and the outlet split is off when I check the air/water. Is it normal for this system?
I appreciate any suggestions.
Thank you very much!

How is the transfer line from the from your TD unit connected to the GC column? This can be a source of air leaks.

We use Markes TDs and the transfer line capillary entering the oven was originally attached to the column using a glass capillary 'sleeve'. We often experienced fairly significant air leaks with this arrangement, so replaced the glass union with an inert steel union from Agilent, which seemed to significantly reduce the amount of air entering the system.

[CrisTheChemist]

In my Perkin elmer TMX350 connected to GCMS shimadzu usually 28 m/z (N2) is about 25% respect to PTFBA 69 m/z peak in tuning and 32 m/z (O2) is about 10% respect to 69. He flow is 1mL/min.

Anyway If tuning is passed, do not mind about N2 and O2 level in my opinion. If you can start mass acquisition from 35 m/z so that you do not see N2 and O2.

[AICMM]

Not having done serious MS in a while, I beg to differ on the N2 question. That much N2 can lead to side reactions (charge transfer) that will affect the compound breakdown significantly. Seen it when I have had helium contaminated with nitrogen.

I would ask if the total flow to the inlet is still 20-30 ml/min even when the column flow is only 1 ml/min to ensure that the inlet is fully bathed in carrier and not a route for air ingress.

Best regards,

AICMM

[yyaann]

Thank you all for your replies, I found a leak at the TD-GC transfer line connection part, the column was not positioned well. It is solved by fixing it.
Best,