“…Doxorubicinol, a major alcohol metabolite of doxorubicin formed by carbonyl reductases 1 and 3, is implicated in off-target cardiotoxicity of doxorubicin-treated patients [3,[7][8][9][10]. High-performance liquid chromatography (HPLC) with fluorescence [11][12][13][14][15][16][17][18][19] or ultraviolet (UV) [20,21] detection, LC with mass spectrometry (LC-MS) [22,23] or tandem mass spectrometry (LC-MS/MS) [24][25][26][27][28][29][30][31][32][33][34][35][36], and capillary electrophoresis [37][38][39] methods have been used to analyze doxorubicin alone or with its metabolite doxorubicinol in various biological matrices, such as blood, serum, plasma, cells, and tissues. Protein precipitation with methanol, acetonitrile, or acetone [13][14][15]18,19,21,22,[25][26][27]31,…”