The Chromium-Diphenylcarbazide Reaction1

Journal of the American Chemical Society (Impact Factor: 12.11). 10/1956; 78(19). DOI: 10.1021/ja01600a014
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    • "DPC forms a colored complex with Cr(VI) (dichromate) at acidic conditions [48], but not with Cr(III). However, DPC can be oxidized to diphenylcarbazone at alkaline conditions and in the presence of oxygen [48], which can form the same colored complex with Cr(III) as DPC forms with Cr(VI) [48]. DPC drops were applied on all unexposed leather samples. "
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    ABSTRACT: About 1-3% of the adult general population in Europe is allergic to chromium (Cr). The assessment of the potential release of Cr(III) and Cr(VI) from leather is hence important from a human health and environmental risk perspective. The Cr(VI) content in leather was recently restricted in the European Union. The aim of this study was to assess possible correlations between the bulk and surface chemistry of leather, released Cr(III) and Cr(VI), and capacities of co-released leather specific species to reduce and complex released Cr. Four differently tanned leathers were characterized by scanning electron microscopy with energy dispersive spectroscopy, X-ray photoelectron spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and the diphenylcarbazide colorimetric method. Their characteristics were compared with results on Cr(III) and Cr(VI) release into artificial sweat (ASW, pH <6.5) and phosphate buffer (PB, pH 7.5-8.0), measured by means of spectrophotometry and atomic absorption spectroscopy. Co-released leather-specific species were shown to reduce Cr(VI), both in ASW and in PB. Their reduction capacities correlated with findings of the surface content of Cr and of released Cr. Leather samples without this capacity, and with less aromatic surface groups visible by ATR-FTIR, revealed Cr(VI) both at the surface and in solution (PB).
    Journal of Hazardous Materials 09/2014; DOI:10.1016/j.jhazmat.2014.08.061 · 4.53 Impact Factor
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    • "The absorbance of the red – violet complex of unknown composition, formed at the pH range of 1.6 – 2.2, is read at 540 nm (Clesceri et al., 2002). Chromium (III) does not react with the DPC reagent (Pflaum et al., 1956). The sample acidification carried out before the DPC addition prevents the solubilization of Cr(III) species, the releasing of Cr(III) from complexes or colloidal particles, or even the increase of Cr(VI) reduction by organic compounds in the sample (Sule et al., 1996). "
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    ABSTRACT: A simple, fast and sensitive spectrophotometric method for the simultaneous determination of Cr(III) and Cr(VI) in effluents and contaminated waters using a UV-visible spectrophotometer, which operates with an advanced software for multicomponent analysis, is proposed. The method consists in the complexation of Cr (III) with EDTA and reaction of Cr(VI) with diphenylcarbazide (DPC). Variables, such as pH and colour stability time, were studied. The effect of concomitant ions on the simultaneous Cr(III) and Cr(VI) determination was also investigated. The sums of the chromium species concentrations obtained by the proposed method were compared with the total chromium concentrations found by electrothermal atomic absorption spectrometry. Recoveries of the chromium species between 75 and 136% were obtained for spiked samples. The linear working range for Cr(III) was 0.5-30 mg L−1, while for Cr(VI) was 0.005-0.30 mg L−1. The detection limits were 0.3 mg L−1 for Cr(III) and 0.003 mg L−1 for Cr(VI) while the quantification limits were 1.0 mg L−1 for Cr(III) and 0.01 mg L−1 for Cr(VI).
    Chemical Speciation and Bioavailability 07/2009; 21(3):153-160. DOI:10.3184/095422909X466095 · 0.59 Impact Factor
  • Analytica Chimica Acta 11/1961; 25(5):507-508. DOI:10.1016/0003-2670(61)80185-2 · 4.51 Impact Factor
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