Validation of a European standard for the determination of hexavalent chromium in solid material

Abstract

A European standard for the determination of Cr(vi) in solid material has been elaborated in the framework of an international co-operation and finally validated in the course of an interlaboratory comparison. The procedure is based on the alkaline digestion prescribed by EPA method 3060A followed by ion chromatography and determines an operationally defined content of Cr(vi), including water-soluble and insoluble chromates. A preliminary robustness study was carried out in order to compare different extraction methodologies and to study the equivalency of different analytical methods for the determination of Cr(vi) in alkaline extracts of soil and waste materials. During an interlaboratory validation trial with 19 European laboratories a set of 4 samples (2 soil and 2 waste samples) was analysed to determine performance characteristics for different combinations of digestion and detection methods. With the procedures prescribed by the new European standard (EN 15192) acceptable results were obtained for both soil samples and one of the waste samples (sludge). However, for the second waste sample (fly ash) a large deviation in analytical results was observed. This indicates that particularly for waste materials a possible occurrence of strong matrix effects has to be considered and supplementary quality control data are needed in order to assess the validity of analytical results. The accuracy of the determination of Cr(vi) in solid matrices remains a challenging field in terms of maximum extraction efficiency and minimum species interconversion.

Evaluation of Hexavalent Chromium Extraction Method EPA Method 3060A for Soils Using XANES Spectroscopy

“…17 The Cr(VI) content in these samples was certified 15 or determined by means of interlaboratory comparisons, 16 using 3060A as an extraction procedure.…”

Simultaneous extraction and catalytic adsorptive stripping voltammetric measurement of Cr(VI) in solid samples

“…The important advantage of this mechanism is the fact that Pb(II) is in the form of a soluble complex. On the contrary, when extraction is carried out using alkaline carbonate solutions, Pb(II) is precipitated in the form of Pb(OH) 2 and during the neutralisation of the extract Cr(VI) can form insoluble PbCrO 4 and the results of Cr(VI) determination are too low [17]. It must be noted that the presence of a complexing agent in the extraction mixture additionally prevents the oxidation of Cr(III) to Cr(VI) as was described in the literature [16,18].…”

Protocol for Extraction and Determination of Cr(VI) in Solid Materials with a High Cr(III)/Cr(VI) Ratio Using EDDS as a Leaching Agent for Cr(VI) and a Masking Agent for Cr(III)

“…Extraction should be able to transfer all forms of Cr(VI) to solution and simultaneously assure no changes in the speciation of chromium. Various extracting solutions to the extraction of Cr(VI) have been used to this time, including 0.28 mol L À1 Na 2 CO 3 þ 0.5 mol L À1 NaOH (the most common extractant) [5 -7], 10 % Na 2 CO 3 þ 2 % NaHCO 3 preceded by an addition of a magnesium sulfate in a phosphate buffer [8,9], 0.1 mol L À1 NaOH with sonication [10], an ammonium sulfate/ammonium hydroxide buffer with the addition of a complexing agent such as EDTA [11] or DTPA [12], and an acetate buffer with the addition of DTPA [13]. These procedures are well examined and comparisons of their application to the extraction of various samples are often described in literature [8, 10 -12, 14, 15].…”