Development and validation of a liquid chromatographic method for the simultaneous determination of four anthracyclines and their respective 13-S-dihydro metabolites in plasma and saliva

A quantitative HPLC method with fluorescence detection has been developed for the simultaneous determination of four anthracyclines (doxorubicin, epirubicin, daunorubicin and idarubicin) and their respective 13-S-dihydro metabolites (doxorubicinol, epirubicinol, daunorubicinol and idarubicinol) in plasma and saliva, using epidaunorubicin as internal standard. A progressive optimization matrix led to a two-step extraction based on a protein precipitation with ethanol followed by a liquid–liquid extraction with dichloromethane after pH adjustment to 8.5. The chromatographic separation was performed in 14 min on a C18 column, applying gradient elution with a mixture of 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The analytes were detected and quantified at an excitation and emission wavelength of 480 and 555 nm, respectively. Limit of detection (LOD) and lower limit of quantification (LLOQ) were 0.3 or 0.75, and 1 or 2.5 ng/mL, respectively. Linearity by means of weighted (1/x) regression was obtained from the LLOQ up to 1000 or 2500 ng/mL for the parent drugs and up to 400 or 1000 ng/mL for the metabolites. Intra-assay and inter-assay relative standard deviation values were all less than 14% at low, medium and high levels, and below 17% at the LLOQ. Accuracy ranged between 91 and 113% at low, medium and high concentrations and between 83 and 118% at the LLOQ. Absolute recoveries were between 78 and 88% in plasma, and between 70 and 79% in saliva, respectively. Autosampler, benchtop, freeze–thaw and long-term stability samples fulfilled acceptance criteria. This selective method was applied successfully to the analysis of plasma and saliva samples from patients administered epirubicin intravenously