The invention comprises a method for the determination of the binding coefficient of a hydrophobic chemical compound comprising: g. Providing an assay plate with a plurality of rows and columns of test vessels; h. Providing the majority of the test vessels in said assay plate with a polymer, wherein in each row the amount of polymer coating per test vessel is increased; i. Filling each test vessel with a solution of binding partner to which the binding coefficient should be assayed, wherein in each column the amount of binding partner is increased; j. Adding the hydrophobic compound and incubate the plate; k. Determining the concentration of said compound in said polymer or in the solution; l. Calculating the protein binding coefficient of the compound.