ELECTROPHORETIC SEPARATION OF INORGANIC ANIONS WITH AN ANION COMPLEXONE-MODIFIED CAPILLARY COLUMN

A twenty-eight-membered macrocyclic polyamine, ,8,12,18,22,26-hexaaza- 1,15-dioxacyclooctaeicosane ([28]ane-N6O2), was covalently bound to fu sed-silica for the electrophoretic separation of simple anions, comple x anions and metal containing anions. Parameters influencing bound lig and complexation properties or the electrophoretic behavior of analyte s, such as the nature of the background electrolyte, the pH and concen tration were investigated. The separation of metallocyanide complexes, Fe(CN)(6)(3-) and Fe(CN)(6)(4-) has been achieved. Supercomplex forma tion resulting from the second-sphere interaction between metallocyani de and polyamine was indicated. The method was effective for the separ ation of arsenite, arsenate, dimethylarsinic acid and phenylarsonic ac id or selenite as well as selenate species. Better resolution of a mix ture of bromide, chloride, sulfate, nitrate, bromate and iodate was ac hieved using an applied potential of -20 kV, with chromate (5 mM, pH 8 .1) as background electrolyte and indirect detection at 270 nm. Linear ity of response, expressed as peak height or peak area was in the rang e of 10(-5)-10(-6) M; detection limits (LODs) based on three times sig nal-to-noise ratio for bromide, chloride, sulfate, nitrate, bromate, i odate, selenate and selenite were all at the femtomole levels. The ani ons present in mineral water and rainwater were also analyzed to evalu ate the quantitative performance of the proposed method. The response mechanism of the prepared capillary column was briefly discussed in te rms of anion complex formation between analytes and the protonated [28 ]ane-N6O2 bound at the silica. surface. (C) 1998 Elsevier Science B.V. All rights reserved.