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Physicochemical properties

Aqueous solubility

The solubility of a compound is an important factor in determining its absorption from the gastrointestinal tract and ultimately its oral bioavailability. Poor solubility can also limit the quality of the data generated in other in vitro assays.

Cyprotex provide both a turbidimetric solubility service and a thermodynamic solubility service for measurement of aqueous solubility. The contrasting features of these methods are described in our online ADME guide.


Lipophilicity is a key determinant of the pharmacokinetic behavior of drugs. It can influence distribution into tissues, absorption and the binding characteristics of a drug, as well as being an important factor in determining the solubility of a compound.

Cyprotex provide a log P (partition coefficient) service using Sirius technology and a log D shake flask service (octanol/buffer) for determining lipophilicity.

pKa determination

The pKa of a molecule predicts the degree of ionization the molecule will have at a particular pH. The ionization potential of a compound affects the distribution of the chemical in solution and affects the availability of the chemical to enter into physical, chemical and biological reactions. The pKa of a compound influences properties such as logD and solubility as well as the absorption, distribution, metabolism, elimination and potency of a compound.

Cyprotex provide a pKa and log P determination assay using a potentiometric titration method technology developed by Sirius.

Chemical Stability

A chemically unstable compound is degraded by non-enzymatic processes, most commonly by hydrolysis, oxidation or light-catalyzed degradation. Cyprotex combines its chemical stability assay with a non-specific binding assay to determine binding of the compounds to the polypropylene plate.

Physicochemical Property Services
turbidimetric solubility
thermodynamic solubility
chemical stability and non-specific binding assessment
pKa and logP
logD shake flask
early formulation assessment
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