Hi Dan,

It depends on the concentration of N and C in the material you want to analyse. Here at Trent we routinely run zooplankton samples with around 10% N and 40% C weighing 0.200mg on our IsoPrime / Eurovector EA and get good 15N and 13C data. If your amphipods have similar bulk compositions then I think its quite possible to analyse individual dried leg samples weighing 0.185mg to the required accuracy and precision. Just be careful to match your standards to your sample sizes.

Michael Isaacs
-----------------
Water Quality Centre
Trent University
1600 Westbank Drive
Peterborough
Ontario
Canada

Email: [log in to unmask]

>>> Daniel Nelson <[log in to unmask]> 02/25/09 12:09 PM >>>
Hi
I'm working with an endangered amphipod.  I would like to do some isotope 
analysis (C&N) to look at diet but I can't sacrafice wild individuals.  However, I 
do have a permit to remove walking legs for genetic analysis.  One large 
amphipod (dried) weighs approximately 4.0 mg and one dried leg weighs 
approximately 0.185 mg.  What is the smallest sample weight that can be 
measured accurately?  Can I analyze individual legs, 3 or 4 legs, or do I need 
to do the whole individual?  I realize the whole individual would probably be 
best but again, I can't sacrafice individuals.  Thanks a lot.

Dan Nelson
MS Student
University of Idaho