Solubility – Shake Flask

This assay is used to determine the solubility of a test article at room temperature in aqueous buffer at pH 7.4.

Required from Sponsor

  • A minimum of 3 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 solubility of the test article, in either mg/mL or µM


  • The test article dissolved in aqueous buffer, pH 7.4, at room temperature

Assay System

  • 1.5 mL shake flask
  • Solubility range by this method of determination: 1.0 µM to 1.0 nM, depending on analytical sensitivity

Assay Conditions

  • This assay is run with a single replicate (n=1)
  • Mix >1.0 mg of test article with 1.0 mL of aqueous buffer, pH 7.4
  • Equilibrate overnight at room temperature (>16 hours), with shaking
  • Filter the solution and sample the filtrate in duplicate (n=2)
  • Determine the concentration of test article using a generic LC-MS/MS method with a minimum 6-point calibration curve


  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. In this assay, it is not determined if a saturated solution is obtained. Thus, the value obtained might not be the true equilibrium solubility of the test article.
  3. In this assay, neither the recovery nor the stability of test article is determined.
  4. Unless told otherwise by the sponsor it is assumed that the test article is 100% pure.