Yes, relative concentrations for different elements within the same sample can be estimated from edge jumps. Be sure to normalize by the difference in absorption coefficient for each edge--you can get those figures from Hephaestus, among other places.

This method won't be as accurate as techniques like ICP or XRF, largely because it's hard to normalize XAS spectra consistently between different edges. But you can easily do better than 20% accuracy.

--Scott Calvin

Sarah Lawrence College