Question

You perform an extraction to remove a compound dissolved in an aqueous layer into an organic layer. 80% of the compound is removed after one extraction. You perform the extraction two more times with equivalent amounts of the organic layer. You should expect to extract approximately how much of the compound from the water?

99.2%

What is the equation to do this?

Answer 1

Distribution constant with an expression

K_j = c_jA/c_jB

where c_jA is the molar concentrations of compound in phase A

c_jB is molar concentration of phase B

The extraction fraction E_j is given below

E_j = q_o/q_total =c_oV_o/c_oV_o+c_wV_w = K_j β/ 1+K_j β

                = 1-1/1+K_j β

q_o thamout of the extracted solvent in the organic phase

q_total is total amount of solute

V_o and V_m are the volume of organic and aqueous phase

β is phase ratio is given by β = V_o / V_w

c_o is molar concentration of analyte in organic phase

c_w concentration in water

K_j is equilibrium constant