Doxorubicin hydrochloride, epirubicin hydrochloride, and acetic acid were all purchased from Sigma Aldrich (Dorset, United Kingdom). Doxorubicinol hydrochloride was purchased from Toronto Research Chemicals (Toronto, Canada). The Analytical Chromatography TLC Silica gel 60 F245 used for the DOX experiments were purchased from Merck/Millipore (Hertfordshire, United Kingdom). The methanol and the acetonitrile were purchased from Fisher Scientific (Loughborough, United Kingdom). The chloroform was purchased from VWR (Leicestershire, United Kingdom). Water was purified using the MilliQ filtration system from Merck/Millipore (Hertfordshire, United Kingdom). Healthy plasma samples and were provided by the Centro di Riferimento Oncologico di Aviano, Italy. The doxorubicin clinical patient samples were supplied by the Department of Pediatric Hematology and Oncology, University Hospital Münster, Germany. Imaging of the TLC plates was performed using a SynGene PXI imaging system (SynGene, Cambridge, United Kingdom). MatLab R2015A was used to write the custom optical quantification program (Mathworks, Cambridge, United Kingdom).