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LogP and LogD Measurements



Readout: logD(pH)

Controls: Testosterone; others available on request


Assay Description:

1 mL of 1-octanol and 1 mL of buffer are added to a glass vial. Compound stock solution (10 mM in DMSO) is added and the vial is rotated for one hour using a shaker at room temperature. The layers are allowed to separate and aliquots of each layer are taken.

Aliquots of the 1-octanol and aqueous solutions are serially diluted using DMSO to give the final samples for LC-MS/MS analysis. Three sequential dilutions are made of each 1-octanol phase, covering a 2500-fold range in concentration. Two sequential dilutions are made of each final aqueous phase, covering a 100-fold concentration range. The MS peak areas from these solutions are used to generate a log(peak area) against log(relative concentration) calibration line. LogD is calculated from the ratio of the 1-octanol relative concentrations to the interpolated aqueous relative concentrations.

The MS detection is performed by using a Sciex API 4000 Q trap instrument. Each compound is analyzed by reversed phase HPLC using a Kinetex 2.6u C18 100 Å column (3.0 mm X 30 mm, Phenomenex). Mobile phase – solvent A: water with 0.1% formic acid,  solvent B: acetonitrile with 0.1% formic acid.


Data Analysis:

LogD is calculated using the following formula:

logD = log {(compound concentration in octanol) / (compound concentration in aqueous phase)}



DMSO                     Dimethylsulfoxide

HPLC                       High-performance liquid chromatography

LC                             Liquid chromatography

MS                           Mass spectrometry



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