Stability of the proteasome inhibitor bortezomib in cell based assays determined by ultra-high performance liquid chromatography coupled to tandem mass spectrometry - Clemens, Jannick; Longo, Magdalena; Seckinger, Anja; Hose, Dirk; Haefeli, Walter E.; Weiß, Johanna; Burhenne, Jürgen (Journal of chromatography, 2014)