Silicas modified by polyelectrolyte complexes for the ion chromatography of anionic complexes of transition metals

Abstract

An approach, which is based on the fact that an anion-exchange layer may be bound at the surface of a cation-exchanger by electrostatic interaction of reversibly-charged functional groups, was used for producing polyelectrolyte anion-exchangers. Water-soluble polymers containing positively charged nitrogen atoms were used instead of anion-exchanging latex. A sulfonated co-polymer of styrene and divinylbenzene was replaced with a sorbent for reversed-phase chromatography (silica coated with dodecylbenzenesulfonic acid). The ion-chromatographic behavior of transition metal complexes with ethylenediaminetetraacetic acid (EDTA) and cyclohexanediaminetetraacetic acid (CDTA) separated on sorbent Silasorb-C₁₈, modified by polyvinylpyridinium bromide (PEVP), polydimetyldiallylammonium chloride (PDMDAA), and polyhexamethyleneguanidine chloride (PGMG) was investigated. The limits of detection were 0.1–1 mg/L and 0.01–0.05 mg/L for single and dual-columns, respectively. A comparison of synthesised Silasorb C₁₈-DBSA-PEVP anion-exchanger with several commercial packed materials (Hiks-1, Anieks, TSK gel IC-Anion-PW, TSK gel IC-Anion-SW, BT XI An, Nucleosil 10 SB) was carried out. It was shown that BT I An and BT II An anion-exchangers cannot be used in determining transition metal complexes with EDTA due to high non-ion-exchange sorption of hydrophobic complex anions on the polymer matrix. Silasorb C₁₈-DBSA-PEVP showed the highest selectivity in separating anion complexes of transition metals with EDTA.