Apologies for the stupid questions but I have confused myself. I was separating out blood components in lab- column chromatography- and now we have to calculate Na+ content of each fraction collected (in μmoles) and the protein content of each fraction in mg. Each fraction was 1.5ml. The Na+ concentration in mM and the protein concentration in mg/ml were read off standard curves. For the sodium, the samples were diluted (0.5ml of blood serum with 9.5ml water). Would I be right to use the full 10ml amount rather than the 0.5ml amount in my calculation? And do- n=c(changed to M) v (changed to litres) = .... then change the finial answer to micro moles. For the protein, I have used Cm= m/v. Again 0.5ml of blood plasma plus 2ml of reagent was used- so would i use the full 2.5ml volume? For my calculation i didn't change the units- not sure if thats right or not. so for example, 5.15mg/ml= m/2.5ml. so m= 5.15 x 2.5= 12.88mg Additionally for the protein, the standard curve line did not go to very low absorption vales, such as 0.006 so I couldn't read off protein concentration value. Could I use the Beer-Lambert Law equation? However i dont know the values of the absorption co-efficient or the path length, so I'm unsure as to how I would do this. I now realised that it asks for moles/mg of each fraction- so i am confused as to which volumes I use for the initial calculations because concentrations were read of standard curves using the diluted volume/ plasma with reagent. Thankyou!