Characterization of an aluminium(III)–citrate species by means of ion chromatography with inductively coupled plasma-atomic emission spectrometry detection

The aluminium(III)–citrate complex (NH4)4[Al2(C6H4O7)(C6H5O7)2]·4H2O was characterized using anion exchange chromatography on-line coupled with the element specific ICP-AES detector. Time-dependent monitoring of individual species in aqueous solution at different temperatures gave information about the species stability and the decomposition pathway. The aluminium–citrate complex (NH4)4[Al2(C6H4O7)(C6H5O7)2]·4H2O disintegrated via an unknown intermediary Al(III)–citrate species from which the thermodynamically stable complex [Al3(C6H4O7)3(OH)(H2O)]4− was formed. The activation energy for the decomposition reaction and the pre-exponential factor were determinated to be Ea = 81.95 kJ mol−1 and A = 3.62 × 1013 s−1.