We are using whole blood samples to determine cobalt concentrations in untreated and cobalt-treated animals. The issue is that the starting volume of whole blood used for sample preparation is not accurate, which introduces bias in the results (i.e. more blood = more cobalt).
We are wondering if there is anything we could use in order to normalise our cobalt results? It would need to be a compound that is consistently present in whole blood (preferably plasma as cobalt increases the number of circulating red blood cells) and be unaffected by cobalt (i.e. there is a possibility that Co2+ might be able to displace and replace other divalent cations such as Ca2+ etc).
I realise this is a total long-shot, but if we can analyse any other element (maybe zinc?) in our samples then we could relate the total cobalt levels back to the starting volume of blood and normalise across treatment groups.