Andrew,

I'm curious how you arrived at a 45/44 ratio of 2 as the maxium enrichment most instruments can handle.  Is it that the instrument can only handle twice as much ion signal or did you take the standard ratio of 0.011237 and multiply it by about 200 because the resistors on the collectors differ by 100?
I have a Finnigan Delta S and I wanted to find these limits of measurement for both C13 and N15.  I would also like to determine the maximum depletion that the instrument can measure.

Thanks,

David DenHaan

National Soil Tilth Laboratory