Extraction and determination of hexavalent chromium in soil samples

Abstract

A procedure for the extraction of Cr(VI) from solid soil-like samples was presented in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract insoluble compounds of Cr(VI). A concentration of DTPA in an ammonium sulphate/ammonium hydroxide buffer equal to 0.02 mol l(-1) was chosen. The conditions of extraction of insoluble Cr(VI) from solid samples were optimised using soil certified reference material spiked with known concentration of insoluble Cr(VI) added as PbCrO(4). The extracts were analysed by adsorptive stripping voltammetry. Validation of the proposed procedure of extraction was carried out by analysis of certified reference material (CRM) 545 and comparison of the results obtained using the proposed and other methods of extraction in the course of analysis of natural soil samples.

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)

“…In earlier studies, it was proved that in the absence of chelating agents the ammonium buffer makes possible the extraction of about 10 to 25% of insoluble Cr(VI), while the addition of a complexing agent (DTPA or EDTA) to the ammonia buffer drastically influences the extractability of total Cr(VI) [11,12]. Predictably, the EDDS also causes an increase of Cr(VI) extraction efficiency.…”

“…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].…”

Sorption Characteristics of Hexavalent Chromium in the Soil Based on Batch Experiment and Their Implications to the Environment

“…At many such sites, leaching and seepage of Cr(VI) from the soils into the groundwater pose a considerable health hazard to both plants and animals (including humans) [5]- [10]. Although both Cr(III) and Cr(VI) are the stable oxidation states of chromium in the environment, Cr(VI) is of particular concern due to its extreme toxicity (100 -1000 times higher than that of Cr(III) [8] [9]. Due to its high solubility and adverse health effects, Cr(VI) poses a significant environmental hazard [11].…”

Determination of Cr(VI) in the Presence of Complexing Agents and Humic Substances by Catalytic Stripping Voltammetry

“…Recently a new procedure for extraction of total Cr(VI) from soil samples was proposed. In the procedure DTPAwas added to the extraction mixture to dissolve insoluble chromates by complexation of the metal ions that form insoluble chromate [18]. Obtained extracts from soil samples contain high concentration of complexing agent and humic substances.…”