Application of diamond thin-film electrodes for the electrochemical detection of trace metal ions

Determination of trace metal ion contamination using anodic stripping voltammetry (ASV) is an established method. The use of boron-doped diamond (BDD) thin-film electrodes as alternates to Hg based electrodes for use in ASV was investigated. This is mainly because of the toxicity of Hg. High-quality conductive diamond is attractive for the detection of trace metal ions due to the material's (i) wide working potential window, (ii) stable surface chemistry and microstructure, (iii) chemically inert surface, and (iv) good activity for metal deposition and stripping reactions. The application of boron-doped microcrystalline and nanocrystalline diamond thin-film electrodes for the analysis of Ag(I), Cu(II), Pb(II), Cd(II), and Zn(II) yielded analytical detection figures of merit comparable and better than those obtained for Hg-coated GC and bare GC, respectively. Limits of quantitation in the low ppb range, good sensitivity, excellent response precision (<4%) and long-term stability (>96%) were obtained.; Nanocrystalline diamond has been found to perform slightly better than the more conventional microcrystalline form of diamond in this application. It was used in conjunction with differential pulse voltammetry (DPASV) to detect these metal ions in lake water, well water, tap water, wastewater treatment sludge, and soil. The electrochemical results were comparable (<10% difference in most cases) with data from inductively coupled plasma mass spectrometric (ICP-MS) and or atomic absorption spectrometric (AAS) measurements of the same samples.; A research goal was to determine how factors such as the diamond surface morphology and chemistry affected the nucleation and growth of metal phases. Scanning electron micrographs of the metal deposits are presented. In general, the fraction of the surface area of the diamond covered by metal deposits was larger for nanocrystalline diamond. This indicates that a larger amount of metal phase formation occurs on nanocrystalline diamond during the preconcentration step, yielding greater sensitivity and lower limits of quantitation in the DPASV measurements.; The quality of the DPASV measurement could be improved if the relatively large peak widths seen in most of our presented data were reduced. We demonstrate the use of pulsed galvanostatic deposition to produce Cu deposits that are nominally smaller in size and more uniformly dispersed over the diamond surface than what is achieved using constant potential or constant current. This in turn leads to relatively sharp and narrow stripping peaks at 40% of the effective deposition time. (Abstract shortened by UMI.)...