Development of new chemotherapeutic drugs is essential as the number of cancer patients is rising all over the world. An important step in pharmacological characterisation of a candidate drug is the study of the drugs pharmacokinetics in human serum. In our study we compare the pharmacokinetics of two Ru based candidate drugs. KP418 is currently undergoing clinical studies, while Q-CYM-08 is a newly synthesised compound. The ability of a drug to bind with serum proteins can influence its efficacy, toxicity and the speed of excretion form the body. For this kind of speciation studies anion exchange (AE) chromatography hyphenated to element-specific detector like inductively coupled plasma mass spectrometry is the most commonly used technique. The biggest limitation of AE chromatography is its inability to separate unbound drug and immunoglobulin bound drug.¹  For this reason we used a previously developed 2D monolithic chromatography method that is a combination of affinity and AE chromatography. Two CIM monolithic disks, the first one is an affinity Protein G disk (binds Fc regions of human immunoglobulins (IgG)) and the second is a weak AE DEAE disk, were combined in a single housing. First a normal gradient elution with NH₄Cl separates the serum proteins on DEAE disk, while IgG remain bound to Protein G disk, followed by an isocratic elution of IgG with acetic acid.²  This enables efficient separation of all the major components of human serum in a single run of 14 min. Protein elution was followed with UV detection and Ru species were detected using ICP-MS with post column isotope dilution to compensate for the drastic differences in eluent composition.