LogD – Shake Flask

This assay is used to determine the LogD of a test article at pH 7.4 using the shake flask method.

Required from Customer

  • Either a minimum of 100 µL of test article at 10 mM in DMSO or 2 mg of powder
  • Exact molecular mass of test article and its salt form
  • MSDS or handling and storage information, e.g., light sensitive, store at -20°C, etc.


  • The measured LogD for testosterone (internal control) at pH 7.4
  • The measured LogD of test article at pH 7.4


  • Test article and testosterone equilibrated at 100 μM total concentration in equal volumes of phosphate buffer and water-saturated octanol

Assay System

  • n-octanol: phosphate buffer at pH 7.4

Assay Conditions

  • Single incubation of test article (n=1)
  • Mix samples for 1 hour at room temperature, then allow to sit for 1 hour at room temperature
  • Sample each phase in duplicate
  • Prepare serial dilutions of the organic and aqueous layers
  • Determine the concentration of the test article in each phase, using a generic LC-MS/MS method with a minimum 6-point calibration curve

Assay QC

  • The LogD of testosterone must be between 3.0 and 3.4 for the test article’s LogD to be accepted


  1. The results from this assay are sent to the sponsor in the ExpressPlus report format, which may include graphical representations of data and comparison with historical data for reference articles.
  2. The LogD value is dependent upon the temperature of the buffer and octanol. The assay is performed at room temperature; we neither monitor nor control the temperature of the aqueous and organic phases.
  3.  This assay can determine the LogD of test articles between approximately -2.0 and 5.0. Data outside this range will be reported as >5.0 or <-2.0.