Cobalt and nickel can be simultaneously determined by formation of their coloured complexes with 8-quinolinol in solution. Molar extinction coefficients are: εCo = 3529, and εNi = 3228 cm-1 M-1 at 365 nm; and εCo = 428.9 and εNi = 0 cm-1 M-1 at 700 nm. Calculate the concentrations of nickel and cobalt in a solution which has absorbances of 0.725 at 365 nm and 0.0710 at 700 nm in a 1 cm cell.

Question

Cobalt and nickel can be simultaneously determined by formation of their coloured complexes with 8-quinolinol in solution. Molar extinction coefficients are:  εCo = 3529, and εNi = 3228 cm-1 M-1 at 365 nm; and εCo = 428.9 and εNi = 0 cm-1 M-1 at 700 nm.  Calculate the concentrations of nickel and cobalt in a solution which has absorbances of 0.725 at 365 nm and 0.0710 at 700 nm in a 1 cm cell.

FilthyF · Answer

DrBob222 Please work your magic!

DrBob222 · Answer

Sorry I was late getting back. I was typing in the answer, I received a call to go to lunch, I had to RIGHT THEN, just now returned. So here goes. I can write that epsilon so I'll use e.
A @ 725 nm = eCo*Ccobalt + eNi*CNickel
A @ 700 nm = eCo*Ccobalt

Calculate C Cobalt at 700, plug into C Cobalt at 725 and solve for C Ni at 725.