THE SYSTEM L-MALIC ACID+OXOVANADIUM(IV) - A POTENTIOMETRIC AND SPECTROSCOPIC STUDY

The equilibria in the system L-malic acid + oxovanadium(IV) in aqueous solution for 1 < pH < 12 have been studied by a combination of potentiometric and spectroscopic methods [electron paramagnetic resonance (EPR), visible absorption and circular dichroism (CD)]. The results of the various methods are made self-consistent in the region 1 less than or similar to 2pH less than or similar to 7, then rationalized assuming an equilibrium model including species MLH-2, MLH-1, ML, MLH, ML2H-2, ML2H-1, ML2, ML2H, ML2H2 (where H2L denotes L-malic acid and M is VO") and several hydrolysis products; their formation constants are given. Some other species were also detected in the region 7 less than or similar to pH less than or similar to 12.