Ion Chromatographic Retention Mechanism of Inorganic Anions on Macrocycle Based Stationary Phase

Maria Concetta Bruzzoniti,a Peter Hajos,b Krisztian Horvath,b Corrado Sarzaninia*

aUniversity of Torino, Department of Analytical Chemistry, Via P. Giuria 5, I-10125 Torino, Italy.
Tel.: +39(011)6707628,
Fax: +39(011)6707615,

University of Pannonia, Department of Analytical Chemistry, Egyetem Utca 10, POB 158, Veszprem, Hungary

Paper based on a presentation at the 12th International Symposium on Separation Sciences, Lipica, Slovenia,
September 2729, 2006.

Retention behaviour of inorganic anions was investigated on a cryptand-based anion exchange column (Cryptand A1) using NaOH and KOH-based eluents. Due to the ability of the macrocycle to bind cations, the positively charged metalcryptand complexes act as anion exchange sites. In addition, cryptand can be partially protonated and in this form also behaves as anion exchanger. Considering the complexation and protonation mechanisms a theoretical retention model and a general equation were developed for describing the simultaneous effect of the nature and concentration of the eluent on the retention factor k. The parameters of the model were iterated and the ion exchange constants were computed, theoretical and experimental data show a good correspondence with correlation coefficients (r2) 0.9987-0.9998 for KOH and 0.9717-0.9883 for NaOH, experimental and computed data differ maximally 5%.

Keywords: ion chromatography, retention mechanism, macrocyclic ligand.