Abstract
A rapid, reliable and accurate method for the determination of hexavalent chromium in Portland cement is developed. The proposed method includes direct spectrophotometric determination of Cr (VI) in Portland cement with 1, 2, 5, 8 Tetrahydroxyanthraquinone, (Quinalizarin, QINZ) at pH 1.5. The European Directive (2003/53/EC) limits the use of cements so that it contains no more than 2 mg.Kg-1 of water-soluble Cr (VI). The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement. The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances). The validity of the method is thoroughly examined and the proposed method gives satisfactory results. A derivative spectrophotometric method has been developed for the determination of total Cr (VI) in Portland cement in the presence of Fe (III) and Ti (IV). The hexavalent chromium complex formed at pH 1.5 allows precise and accurate determination of chromium (VI) over the concentration range 0.05 to 3.0 mg.L-1of chromium (VI). The validity of the method was examined by analyzing several Standard Reference Material (SRM) Portland cement samples. The MDL (at 95% confidence level) was found to be 25 ng/mL for chromium (VI) in National Institute of Standards and Technology (NIST) cement samples using the proposed method.
Highlights
In cement industry, raw materials are mixed in controlled proportions and ground to form a fine and homogeneous mixture called raw meal
The absorbance at 565 nm due to Cr (VI)-QINZ complex is recommended for the determination of water-soluble Cr (VI) in Portland cement
The quantification of Cr (VI) released from cement when mixed with water is performed according to TRGS 613 (Technical Rules of Hazardous Substances)
Summary
Raw materials are mixed in controlled proportions and ground to form a fine and homogeneous mixture called raw meal. The US EPA, ASTM, OSHA and NIOSH and other agencies have established many of these analytical procedures as required test methods. These methods include a range of instrumental techniques including UV-Visible spectrophotometry, atomic absorption spectrophotometry (AAS), ion chromatogramphy (IC), capillary electrophoresis (CE), XRF and inductively coupled plasma (ICP) by either emission or mass spectrometry. Fundamental study of the complexation reaction of hexavalent chromium with QINZ is described, a rapid and sensitive first derivative ratio spectrum zero-crossing method is undertaken to determine Cr (VI) in the presence of Fe (III) and Ti (IV) in mixtures using Quinalizarin as a complexing agent. The validity of the method is thoroughly examined and its analytical characteristics are determined and approved to be suitable for the intended purpose
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