Preliminary BCS Solubility Classification – Shake-Flask

This non-GLP assay is used to determine a preliminary BCS solubility classification by measuring the quasi-equilibrium solubility of a test compound in aqueous USP buffer systems at two pH values between 1.0 and 7.4

Required from Customer

  • A study design—the customer must specify the values of several assay variables listed in the Options section
  • Minimum 50 mg of test compound in powder form
  • Highest human dose strength
  • pKa of test compound
  • Molecular mass (exact mass) of test compound and its salt form
  • MSDS or handling and storage information, e.g., light-sensitive, store at -20°C, etc.


  • Solubility of test compound at two pH values specified by the customer between 1.0 and 7.4
  • Preliminary BCS solubility classification


  • Test compound dissolved in an appropriate dosing vehicle

Assay System

  • 1.5 mL shake flask

Assay Conditions

  • Three independent determinations (N=3)
  • Combine test compound with aqueous buffers  then vortex solution for circa 2 hours
  • Let solution sit for at least 8 hours at 37°C
  • Inspect visually for undissolved powder
  • As needed filter the solution
  • Prepare duplicate (N=2) samples for injection into the LC/MS/MS
  • Determine the concentration of test compound using a generic LC-MS/MS method with a minimum 4-point calibration curve


  1. In this assay it is not determined when and if a saturated solution is obtained. Because of this the solubility value obtained might not be the true equilibrium solubility of the test compound.
  2. In this assay neither the recovery nor the stability of the test compound is determined.
  3. Unless told otherwise by the customer it is assumed that the test compound is 100% pure.The assay is often done in conjunction with EA903, Preliminary BCS Permeability.


  1. The customer must specify:
    • either the  standard or custom report format
    • the two pH at which the solubility is measured—typically 2.0 and 7.4
    • the buffer systemThe customer can request additional replicates