Aim: To determine the red blood cell to plasma partitioning and whole blood to plasma ratio of test compound.

Background information: During the screening of compounds in Drug Discovery, plasma is the most preferred biological matrix for their quantification. However, pharmacokinetic parameters calculated from plasma data may be misleading if differences exist between drug concentrations in plasma and red blood cells (RBC). The blood to plasma ratio provides an indication of drug binding to red blood cells. The degree of red blood cell partitioning determines whether blood or plasma should be used for future pharmacokinetics studies. 

Test compound is spiked into fresh heparinised whole blood and control plasma. After incubation, the whole blood is centrifuged. Test compound is quantified in control plasma and plasma fraction from whole blood by UPLC-MS/MS.