| As a chelating agent,nitriotriacetic acid has a large number of coordination atoms and small molecular weight,which shows good complexability for many metal ions.Compared with other chelating agent,it is cheap and biodegradable.As a new carbon nano-materials,acetylene black and carbon nanotubes are the first choice of modification materials,which large specific surface area,strong adsorption capacity and good conductivity.In this paper,the modified carbon paste electrode was prepared by direct mixing method with nitriotriacetic acid,acetylene black,nitrilotriacetic acid/carbon nanotubes composites and acetylene black/nitrilotriacetic acid composites as modifiers.Its response to heavy metal ions such as lead,mercury,cadmium and cobalt were studied by cyclic voltammetry.The main contents are as follows:?1?Nitrilotriacetic acid modified carbon paste electrode was prepared,Electrochemical behaviors of lead ion at the bare carbon paste electrode and nitrilotriacetic acid modified carbon paste electrode were investigated by cyclic voltammetry.The experimental results showed that lead ion had obvious redox peak on the nitriotriacetic acid modified carbon paste electrode.The mechanism of electrode reaction was speculated and the detection conditions were optimized,under this conditions,the oxidation peak currents were proportional to lead ion concentration in the range of 1.0×10-79.0×10-6mol/L with the detection limit of1.83×10-88 mol/L.The electrode had good reproducibility and stability,the trace amounts of lead ion in simulated water samples were successfully detected by standard addition method.?2?Electrochemical behaviors of mercury ion at the bare carbon paste electrode and acetylene black modified carbon paste electrode were investigated by cyclic voltammetry.The experimental results showed that mercury ion had obvious redox peak on the acetylene black modified carbon paste electrode.The detection conditions were optimized,under this conditions,the oxidation peak currents were proportional to mercury ion concentration in the range of 3.0×10-72.4×10-55 mol/L with the detection limit of 2.30×10-88 mol/L.The trace amounts of mercury ion in simulated water samples were successfully detected by standard addition method.?3?Nitrilotriacetic acid/carbon nanotubes composites modified carbon paste electrode was prepared,cyclic voltammetry determination of cadmium ions.The experimental results showed that the response performance of the electrode to the cadmium ion was the best under the condition of a pH 7.50 PBS buffer solution with a scanning speed of 140 mV/s and a scan range of 0.8-0.2 V.Under this conditions,the oxidation peak currents were proportional to cadmium ion concentration in the range of 1.0×10-71.0×10-44 mol/L with the detection limit of 3.70×10-88 mol/L.The electrode had good reproducibility and stability,the trace amounts of cadmium ion in simulated water samples were successfully detected by standard addition method.?4?Acetylene black/nitrilotriacetic acid composites modified carbon paste electrode was prepared,Electrochemical behaviors of cobalt ion at the bare carbon paste electrode,nitrilotriacetic acid modified carbon paste electrode and acetylene black/nitrilotriacetic acid composites modified carbon paste electrode were investigated by cyclic voltammetry.The experimental results showed that cobalt ion had obvious redox peak on the acetylene black/nitrilotriacetic acid composites modified carbon paste electrode.The detection conditions were optimized,under this conditions,the oxidation peak currents were proportional to cobalt ion concentration in the range of 2.0×10-72.8×10-55 mol/L with the detection limit of4.30×10-8mol/L,and the correlation coefficient was 0.9993.The trace amounts of cobalt ion in simulated water samples were successfully detected by standard addition method. |
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