Article

The Chromium-Diphenylcarbazide Reaction1

04/2002; DOI: 10.1021/ja01600a014
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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).
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    ABSTRACT: The aim of this study was to compare two different widely-used methods for the determination of hexavalent chromium (Cr(VI)) in water samples by Electrothermal Atomic Absorption Spectrometry (ETAAS). Both methods are based on the complexation - reaction of Cr(VI) with an organic complexation reagent, which is then extracted and preconcentrated in organic solvent. In the first method, ammonium pyrrolidine dithiocarbamate (APDC) is used as complexation reagent, whereas 1,5-diphenylcarbazide (DPC) is used in the second method. The speciation methods were optimized and validated. Both methods were applied for the determination of Cr(VI) in the same multi-level groundwater samples (0.060 – 42 μg/L, n=13) and the results were compared statistically. Beside the comparison of the two extraction methods (APDC, DPC), the samples were also analyzed by Reagent Free Ion Chromatography (RFIC) with conductivity detector and statistical comparison was also performed. Paired t-test was applied and the results indicated that there was no statistically significant difference between the three methods. Useful conclusions about the analytical performance of these widely-used-in-routine-labs methods were drawn. The selectivity of Cr(VI) determination was significant for both methods. The DPC method had lower limit of detection than APDC, however the APDC method was more robust than the DPC method. Both methods are appropriate for the determination of Cr(VI) in different ground water samples at sub-μg/L levels.
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    ABSTRACT: Chromium(VI) salts are possible contaminants of the chromium(III) pigments used as colorants in eyeshadow preparations. The use of products containing these contaminants poses acute risks for sensitization and contact allergies. Chromium(VI) compounds are also classified as carcinogenic to humans (IARC group 1). An analytical method to analyse trace levels of chromium(VI) in eyeshadow was developed in this study. The method is based on an extraction of the chromium(VI) from the sample using a maximum extraction with alkali and additionally with synthetic lachrymal fluid to simulate physiological conditions. Following derivatization with 1,5-diphenylcarbazide, the extracted chromium(VI) is then quantified by spectrophotometry (540 nm). Validation tests indicated a method standard deviation (inter- and intraday) of 8.7% and a linear range up to 25 mg/kg. The average recovery was 107.9%, and the detection limit was 2.7 mg/kg. The applicability of the procedure was confirmed by the analysis of pigments and authentic eyeshadow matrices.
    International Journal of Spectroscopy 01/2012; 2012(2):Article ID 985131.

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