Electrophoretic separation of inorganic anions with an anion complexone-modified capillary column

Abstract

A twenty-eight-membered macrocyclic polyamine, 4,8,12,18,22,26-hexaaza-1,15-dioxacyclooctaeicosane ([28]ane-N 6O 2), was covalently bound to fused-silica for the electrophoretic separation of simple anions, complex anions and metal-containing anions. Parameters influencing bound ligand complexation properties or the electrophoretic behavior of analytes, such as the nature of the background electrolyte, the pH and concentration were investigated. The separation of metallocyanide complexes, Fe(CN) 6 3− and Fe(CN) 6 4− has been achieved. Supercomplex formation resulting from the second-sphere interaction between metallocyanide and polyamine was indicated. The method was effective for the separation of arsenite, arsenate, dimethylarsinic acid and phenylarsonic acid or selenite as well as selenate species. Better resolution of a mixture of bromide, chloride, sulfate, nitrate, bromate and iodate was achieved using an applied potential of −20 kV, with chromate (5 m M, pH 8.1) as background electrolyte and indirect detection at 270 nm. Linearity of response, expressed as peak height or peak area was in the range of 10 −5–10 −6 M; detection limits (LODs) based on three times signal-to-noise ratio for bromide, chloride, sulfate, nitrate, bromate, iodate, selenate and selenite were all at the femtomole levels. The anions present in mineral water and rainwater were also analyzed to evaluate the quantitative performance of the proposed method. The response mechanism of the prepared capillary column was briefly discussed in terms of anion complex formation between analytes and the protonated [28]ane-N 6O 2 bound at the silica surface.