Notes: MitoB-d15 is intended for use as an internal standard for the quantification of MitoB (Item No. 17116) by GC- or LC-MS. MitoB is a ratiometric mass spectrometry probe that can be used for assessing changes in H2O2 within mitochondria in vivo. MitoB contains a triphenylphosphonium cation component that drives its accumulation in mitochondria where its arylboronic moiety selectively reacts with H2O2 to produce a phenol product, MitoP (Item No. 17117).{27787,27786} Quantifying the MitoP/MitoB ratio by LC-MS/MS reflects the mitochondrial matrix H2O2 concentration.