Simultaneous Electrochemical Detection of Co(II) and Cu(II) by 1-Diazo-2-Naphthol-4-Sulfonic Acid/MWCNTs Modified Electrode

This work describes a simple preparation of 1-diazo-2-naphthol-4-sulfonic acid (1,2,4-acid) and multiwalled carbon nanotubes (MWCNTs) modified glassy carbon electrode (GCE) for the simultaneous detection of Co(II) and Cu(II). MWCNTs, with their good conductivity and large surface area, were drop-casted onto the surface of the GCE prior to the electrodeposition of 1,2,4-acid, a metal chelating agent. Co(II) and Cu(II) were simultaneously measured by differential pulse anodic stripping voltammetry (DPASV) in a batch system. Under optimum conditions, the linear range of Co(II) was between 0.10 and 2.5 mu gmL(-1) with an LOD of 80 ngmL(-1). Two linear ranges were obtained for Cu(II), 0.0050 to 0.030 mu gmL(-1) and 0.040 to 0.25 mu gmL(-1),with an LOD of 2.4ngmL(-1). The method offered a high operational stability for up to 52 measurements (RSD=3.4% for Co(II) and 2.6% for Cu(II)) and good reproducibility (RSD=1.2% for Co(II) and 1.7% for Cu(II)). In the simultaneous detection of Co(II) and Cu(II), there was no effect from common interferences found in wastewater. The method was successfully applied in real water samples with good recoveries (88.2 +/- 0.8 to 102.0 +/- 0.8% for Co(II) and 96.5 +/- 0.4 to 103.8 +/- 0.9% for Cu(II)) and the results were in good agreement with those obtained from inductively coupled plasma optical emission spectrometry (ICP-OES) (P > 0.05).