Differential pulse anodic stripping voltammetric determination of cadmium(II) with N-p-chlorophenylcinnamohydroxamic acid modified carbon paste electrode

A sensitive voltammetric method has been developed for the determination of cadmium(II) utilizing a carbon paste electrode modified with N-p-chlorophe nylcinnamohydroxamic acid. The analyte was accumulated at the modified elec trode surface (via complexation) under open circuit and precisely controlle d convective condition. It was then quantified electrochemically by differe ntial pulse anodic stripping voltammetry in a different nondeaerated electr olyte solution following medium exchange Detailed experiments were conducte d to establish the optimal carbon paste composition, pH and concentration o f accumulation and stripping solutions, preconcentration time, bulk cadmium (II) concentration, aid instrumental parameters. Two good linearities were obtained between the voltammetric curl ent and cadmium concentration centra tion employing different preconcentration limes. One was acquired ill the c oncentration range 2.00 x 10(-7)-3.20 x 10(-6) M Cd(II) (r = 0.999) and the other from 4.00 x 10(-8) to 1.60 x 10(-7) M Cd(II) (I = 0.999) with 1 min and 2 min preconcentration time, respectively. The detection limit was foun d to be 9.80 x 10(-9) M (1.1 ppb) Cd(II) with 2 min preconcentration time. For a series of six determinations of Cd(II) at 1 x 10(-6) M and 8 x 10(-8) M levels relative standard deviations of 2.6% and 5.5%, respectively, were achieved. Electrochemical cleaning was used to regenerate the surface rapi dly and reproducibly; and this allows the use oi a single modified electrod e surface in multiple analytical determinations over several weeks. Many co mmon metal ions had little or no effect on the determination of cadmium(II) . The method was verified by the determination of trace cadmium(II) in muni cipal and mineral waters.