Diamond paste electrodes for inorganic analysis

Abstract

Differential pulse voltammetry is one of the most widely used analytical polarographic techniques especially for trace inorganic analysis. Up to now mercury electrode and different types of carbon electrodes were used for such analysis. The emphasis of the present dissertation is on the design of a new class of electrodes, namely mono crystalline diamond paste based electrodes, to be used in differential pulse voltammetry for trace analysis of inorganic compounds. Monocrystalline diamond and boron doped polycrystalline diamond based electrodes exhibit several superior electrochemical properties that are significantly different from those of other carbon allotropes based electrodes, e.g., glassy carbon electrodes, highly oriented pyrolytic graphite based electrodes, which have been widely used for many years. The advantages are: (a) lower background currents and noise signals, which lead to improve SIB and SIN ratios, and lower detection limits; (b) good electrochemical activity ( pre-treatment is not necessary); (c) wide electrochemical potential window in aqueous media; (d) very low capacitance; ( e) extreme electrochemical stability; and (f) high reproducibility of analytical information. Furthermore, later studies shown the superiority of the mono crystalline diamond as electrode material due to high mobilities measured for electrons and holes. The design selected for the electrodes is simple, fast and reproducible. The diamond powder was mixed with paraffine oil to give the diamond paste used as electroactive material in the electrodes. The results obtained by employing the diamond paste based electrodes proved a high sensitivity, selectivity, accuracy and high reliability. These characteristics made them suitable to be used for the analysis of different cations (e.g., Fe(ll), Fe(Ill), Cr(Ill), Cr(VI), Pb(ll), Ag(I)) as well as of anions (e.g., iodide) in pharmaceutical, food and environmental matricies.