Analysis of metal complexes in the presence of mixed ion pairing additives in capillary electrophoresis

It was demonstrated that metal complexes were successfully separated by capillary electrophoresis with mixed ion pairing agents in the running buffer. The migration behavior of metal complexes in the presence of the ionic additives ammonium, tetramethylammonium, tetraethylammonium, and tetrabutylammonium is discussed. 4-(2-Pyridylazo)resorcinol (PAR) was selected as the chelating reagent for the pre-column derivatization with Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) ions. Under optimum conditions [10 mM NaH2PO4-Na2HPO4 as the running buffer containing 1.10(-4) M PAR, 5 mM tetramethylammonium and 5 mM tetrabutylammonium as the mixed ionic additives, pH 8.0, 70 cm (62.5 cm effective length)x50 mu m capillary, separation voltage: 30 kV, injection time: 5 s, detection wavelength: 510 nm], the separation of six analytes was accomplished in 9 min. Excellent linearity with a dynamic range of two orders of magnitude from 1.10-4 to 1.10(-6) M was obtained. The detection limits of Fe(II), Co(II), Ni(II), Cu(II) and Zn(II) were 6.80.10(-7), 3.36.10(-7), 3.27.10(-7), 2.64.10(-7) and 6.63.10(-7) M, respectively. This method was applied to the analysis of some metals in a pharmaceutical sample and an anode slime sample. (C) 1999 Elsevier Science B.V. All rights reserved.