title: Diamond paste-based electrodes for determination of Cr(III) in pharmaceutical compounds.
abstract: A new class of monocrystalline diamond paste-based electrodes is proposed for the determination of chromium(III) at trace levels in vitamins. Three types of monocrystalline diamond-natural diamond 1mu (natural diamond), synthetic diamond 50mu (synthetic-1), and synthetic diamond 1mu (synthetic-2)-were used for electrode construction. The linear concentration ranges are between 10(-10) and 10(-8); 10(-9) and 10(-7), and 10(-10) to 10(-8) mol L(-1), with limits of detection of 10(-12), 10(-12), and 10(-11) mol L(-1), when natural diamond, synthetic-1, and synthetic-2, respectively, are used as electrode materials. For electrodes based on natural diamond and synthetic-1 it was found that Cr(III) yields a peak at about +0.275+/-0.015 V (vs. Ag/AgCl) within a predetermined positive potential range situated between +0.4 and +0.2 V, while for the electrode based on synthetic-2 the peaks are found at +0.300+/-0.015 V (vs. Ag/AgCl). The proposed method is reliable for the determination of chromium(III) at trace levels in two vitamin tablets (RSD<0.2%).
authors.affiliation: Department of Chemistry, University of Pretoria, 0002, Pretoria, South Africa. Raluca.Stefan@chem.up.ac.za
authors.forename: Raluca-Ioana
authors.initials: RI
authors.lastname: Stefan
authors.forename: Semere Ghebru
authors.initials: SG
authors.lastname: Bairu
authors.forename: Jacobus Frederick
authors.initials: JF
authors.lastname: van Staden
mesh_terms: D002857:Chromium / Q000032:analysis* / Q000737:chemistry*; D018130:Diamond / Q000737:chemistry*; D004566:Electrodes; D013607:Tablets / Q000737:chemistry*; D014815:Vitamins
chemical_list: D013607:Tablets; D014815:Vitamins; D002857:Chromium; D018130:Diamond