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

Abstract

The aluminium(III)–citrate complex (NH 4) 4[Al 2(C 6H 4O 7)(C 6H 5O 7) 2]·4H 2O 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 (NH 4) 4[Al 2(C 6H 4O 7)(C 6H 5O 7) 2]·4H 2O disintegrated via an unknown intermediary Al(III)–citrate species from which the thermodynamically stable complex [Al 3(C 6H 4O 7) 3(OH)(H 2O)] 4− was formed. The activation energy for the decomposition reaction and the pre-exponential factor were determinated to be E a = 81.95 kJ mol −1 and A = 3.62 × 10 13 s −1.