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)₄Al₂(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)₄Al₂(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 E_a = 81.95 kJ mol⁻¹ and A = 3.62 × 10¹³ s⁻¹.