100 mg of ibuprofen has mixed with 25 mL octanol and 25 mL water inside a separa
ID: 518880 • Letter: 1
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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