100 mg of ibuprofen has mixed with 25 mL octanol and 25 mL water inside a separa

Question

100 mg of ibuprofen has mixed with 25 mL octanol and 25 mL water inside a separating funnel in order to determine its partition coefficient. After aqueous and organic phases are separated, determination of absorption of aqueous phase and construction of a calibration curve using UV-spectrophotometer has been applied. Concentration of ibuprofen in aqueous phase (water) is found to be 0.0125 mg/mL.

Draw the separation setup (show organic and aqueous phases). And calculate the partition coefficient (log P) of this drug.

Explanation / Answer

Based on Information....

For calculation of partion coefficient we need to find concentration of ibuprofen in each phase.

concentration of ibuprofen in water = 0.0125 mg/mL

so for 25mL = 0.0125*25 = 0.313 mg / 25mL

concentration of ibuprofen in octanol = 100 mg - 0.313 mg = 99.69 mg / 25ml

to calculate a partition coefficient between two solvents, the concentration of the first solvent mentioned goes on top of the Kpc expression

Kpc = concentration of ibuprofen in octanol / concentration of ibuprofen in water

Kpc = 99.69 mg / 25ml / 0.313 mg / 25mL = 318.48

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