Preparation of the 25mM stock solution
Calculation  of dried metal complex to be used as follows,  n = C x V, n = 25x10-3 M x 500x10-6 L = 12.5x16-6 mol.  
M = n x Mw,  12.5x16-6 mol  x  588g/mol = 0.00736g
0.