Anodic stripping voltammetry at a new type of disposable bismuth-plated carbon paste mini-electrodes.

A new type of disposable carbon paste mini-electrodes (CPmEs), with dimensions in the 50-300 microm range, have been fabricated by heat-shrinking the end-tip of plastic micropipette tips and filling them with carbon paste. The CPmEs have been characterized by microscopic and electrochemical means and tested as substrates for in situ plated Bi film electrodes (BiF-CPmEs), used in the determination of heavy metals by square wave anodic stripping voltammetry (SWASV). It was found that this new class of CPmEs combines the advantages of carbon paste electrodes (readily renewable surface and high surface area) with those of near-microelectrode behaviour (no stirring or electrolyte excess needed). During SWASV experiments in unstirred Pb(II) and Cd(II) solutions well-shaped stripping peaks were obtained whose height varied linearly with analyte concentration in the wide 1x10(-8) to 10(-6) M range, both in acetate buffer and unbuffered solutions. Under optimal conditions detection limits of 8x10(-10) and 1.3x10(-9) M were achieved for Pb(II) and Cd(II), respectively and in a trial application, these metal ions have been determined in a spiked tap water sample using a BiF-CPmE.