DETERMINATION OF COPPER AT SURFACE-MODIFIED ELECTRODES - EFFECTS OF COMPETITIVE-BINDING AND ELECTRODE SIZE

Electrodes modified with electropolymerized films of [Ru(v-bpy)3]2+ in to which Xylenol orange, Eriochrome cyanine R, Nitroso R salt or Batho cuproine sulfonate were incorporated by ion exchange can be used to de termine copper in solution with high sensitivity, excellent linearity and a dynamic range of over two orders of magnitude. The presence of i ron, cobalt, nickel, chloride or bromide does not alter the response m easurably. Oxalate anions produce a steady increase in the current mea sured at the potential for oxidation of the copper complexes. The pres ence of phosphate anions in the preconcentration solution also gives r ise to an enhanced signal. The use of modified microelectrodes (75 mum diameter) or ultramicroelectrodes (5 mum diameter) results in an enha ncement in the sensitivity, although a saturation response is obtained for copper concentrations above 6 x 10(-6) M. Ultramicroelectrodes mo dified with Bathocuproine sulfonate could be used in multiple determin ations with good reproducibility (+/- 9%) and without the need for rem odification of the electrode surface.