Hi, Everyone,
 
   We are using Isoprime IRMS to run CO2 samples in DI mode. After the
ion source was cleaned, we run background scan (Nupro Valve Closed), the
N2 signal is ~12 e-12, it is much higher than before (0.8 e-12) and
above the acceptable value (5 e-12). However, the other signals, such as
H2O, O2, Ar, are not excess of their maximum acceptable values. 
    And to our experience, if there is a leak, Ar and H2O would show a
higher than normal background. Does anyone know what else may be causing
the high N2 background if it is not the leak? Any suggestion would be
greatly appreciated. 
 
 
Wendy Zhang
Air Quality Research Division
Environment Canada 
4905 Dufferin Street
Toronto, Ontario M3H 5T4
Tel: (416) 739-5792 (office)
Tel: (416) 739-5822 (lab) 
Fax: (416) 739-4664
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