Question

A standard analytical procedure for measuring the aqueous concentration (Cw) of a highly hydrophobic compound with a low aqueous saturation solubility (Cwsat) is to first extract the

hydrophobic compound from a large volume of water into a smaller volume of organic solvent such as octanol,and then analyze the concentration of the hydrophobic compound in the organicsolvent (Coct) .What volume of octanol is required to extract 99.9% of pyrene present in 1 L of a water sample?Assume thermodynamic equilibrium and a constant temperature of 25oC? Pyrene, C16H10, MW = 202.26 grams/mole

Answer 1

We will use multiple extraction for this method, as multiple extraction gives effective results.

Let

Xn = amount extracted = 99.9% of amount initially present (0.999x)

v = volume of water = 1L

V = volume of octanol = ? to be calculated

But this is possible when we know the number of extractio , as if we have n=1 then also we can put the values to calculate V

Volume of octanol = volume of water - (0.001)volume of water / 0.001 X Kd

0.001 = Amount left in water

Kd = distribution coeffecient

volume of water = 1L

Kd= Not given

however we need Kd for this

If we have Kd

Then