A bismuth/multi-walled carbon nanotube (Bi/MWNT) composite modified electrode for determination of cobalt by differential pulse adsorptive cathodic stripping voltammetry is described. The electrode is fabricated by poten-tiostatic pre-plating bismuth film on an MWNT modified glassy carbon (GC) electrode. The Bi/MWNT composite modified electrode exhibits enhanced sensitivity for cobalt detection as compared with the bare GC, MWNT modified and bismuth film electrodes. Numerous key experimental parameters have been examined for optimum analytical performance of the proposed electrode. With an adsorptive accumulation of the Co(Ⅱ)-dimethylglyoxime complex at -0.8 V for 200 s, the reduction peak current is proportional to the concentration of cobalt in the range of 4.0 × 10~(-10)-1.0×10~(-7) mol/L with a lower detection limit of 8.1×10~(-11) mol/L. The proposed method has been applied successfully to cobalt determination in seawater and lake water samples.
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