Dear Isogeochem,

    I am working on the denitrifying method in order to analyze  
nitrate in ground water samples. I wonder whether anyone has advice on  
this method, which involves using bacteria to convert nitrate to  
nitrous oxide. The nitrous oxide is then concentrated in a  
Preconcentrator and analyzed on A GV Instruments mass spec.
    Although tests have shown that my bacteria have removed all  
nitrate and nitrite, the peak heights of analyzed nitrous oxide are  
only around 1 nA. In terms of storage, I have suspended them in  
glycerol in a -80 degree freezer, where they have been for the past 9  
months. However, it was suggested to me that genetic drift may result  
in strains that no longer work properly.
   If anyone has any advice or knowledge about these issues, I would  
love to hear from you.


Tiffany Yesavage
Graduate Student
Colorado School of Mines
Department of Geology and Geological Engineering