Chemija / Chemistry
 ISSN 0235-7216 ISSN 2424-4538 (online) |
2011 m. Nr. 4 Determination of chromium in cement by catalytic adsorptive stripping voltammetry
Chromium determination in cement by catalytic adsorptive stripping voltammetry using a hanging mercury drop electrode is described. The composition of medium for Cr(VI) determination is the following: CH3COONa 0.15 mol l–1, diethylene- triaminepentaacetic acid 5 mmol l–1, NaNO3 0.7 mol l–1, pH 6. The optimal voltammetry conditions: accumulation potential –0.9 V, accumulation time 5–10 s, square wave voltammetry stripping mode. The detection limit for Cr(VI) is about 0.05 μg l–1, and the relative standard deviation does not exceed 3%. Chromium species are extracted from cement with water or nitric acid. The total chromium is determined after the quantitative oxidation of Cr(III) to Cr(VI) by addition of 0.1–0.3 mmol l–1 of permanganate ions to the cement extracts. The concentration of Cr(III) is evaluated as the difference between total chromium and Cr(VI).
Keywords: chromium, speciation, catalytic adsorptive stripping voltammetry, hanging mercury drop electrode, cement |
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