Chromium(vi) Toxicity to Luminescent Bacteria

Abstract

The toxicity of chromium(VI) to luminescent bacteria was determined using the Microtox bioassay. The aim of this study was to assess the influence of pH on the toxicity of Cr(VI) samples because its speciation depends on this parameter. A Microtox test basic protocol, modified to assure the same pH in all the cuvettes, was used to determine the toxicity of the Cr(VI) compounds. In the range studied, 4.6 to 9.3, the observed EC50 values increased with the pH (31-1,184 mg/L Cr(VI)). These toxicity results were related to the percentage of the different Cr(VI) species. Hydrogenchromate anion was found to be the most toxic species. In general, only slight differences in toxicity were found when the Microtox test basic protocol was used. Nevertheless, when 20.4% (w/v) sucrose was used as an alternative medium to 2% (w/v) NaCl, the results obtained could not be compared because the sensitivity of the bacteria in this medium was found to be different. The influence of an exposure-time effect was also evaluated. In 2% (w/v) NaCl medium, the toxicity increased with time, which indicates a slow response of the bacteria to the toxin. Keywords-Chromium(VI)Toxicity Microtox pH effect Exposure-time effect

Synthesis of thiol amine surfactant for sensor fabrication to determine chromium(III) ions in different water samples

“…Among those, the detection of chromium had more attention due to the high toxicity of Cr(VI), while Cr(III) is considered less toxic and unexpectedly necessary to human health in trace concentration. The reverse effects of higher concentration of Cr(III) comes from its high coordination ability with different organic compounds, resulting in inhibiting some metallicenzyme systems [3,4]. The allowed limit for aqueous effluent discharged into inland waters is 1.0 mg L -1 for total chromium (Cr(III) and Cr(VI)) and 0.10 mg L -1 for Cr(VI) [5,6].…”