Dear all,
when the automatic background subtraction using Isodat 2.0  gave
inaccurate isotope value, I want to integrate the peak manually. There are
three tools in Isodat 2.0 which can be used, define peak, define
background, and scan.
Do you have any idea how to use these tools correctly in order to achieve
precise and accurate isotope value? I used the method of define
background, and then the peak was defined with a negative background for
44CO2. I am wondering why it is negative. Can you explain this? Thank you
very much.

Best regards
Lijun Zhang