The Chromium-Diphenylcarbazide Reaction1

Journal of the American Chemical Society (Impact Factor: 12.11). 10/1956; 78(19). DOI: 10.1021/ja01600a014


A study of the nature of the chromium-diphenylcarbazide reaction was carried out. Absorptimetric data for the reactions of chromium(VI), chromium(III) and chromium(II) ions with diphenylcarbazide and diphenylcarbazone were compared. The stoichiometry of the various systems was determined together with the effects of pH and the extractability of the colored reaction product into non-aqueous media. The behavior of the colored complex under the influence of an electric field was observed. The nature of the highly absorbing complex formed in the reaction of chromium and the organic reagents was postulated.

  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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).
    Full-text · Article · Sep 2014 · Journal of Hazardous Materials
  • Source
    • "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). "
    [Show abstract] [Hide abstract]
    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).
    Preview · Article · Jul 2009 · Chemical Speciation and Bioavailability
  • [Show abstract] [Hide abstract]
    ABSTRACT: Potassium peroxydisulfate is recommended as a reagent for the mineralization of organic materials, such as sutures, for chromium determination. After dissolution of the fusion mixture, hypobromite oxidation is carried out to transform the chromium into the hexavalent state. Excess oxidant is removed and the chromium is reacted with s-diphenylcarbohydrazide in a solution of pH 1.1. A large excess of reagent is needed to achieve linearity of the calibration curve. The time for a single determination, including weighing the dried sample is less than 15 minutes. The standard deviations on 3–12 mg. samples containing 0.4–0.8% Cr2O3 is ±0.006%. The method is easily adapted to macro samples as well as chromium trace analysis.
    No preview · Article · Nov 1958 · Microchemical Journal
Show more