Determination of Cr(VI) in plants by electrothermal atomic absorption spectrometry after leaching with sodium carbonate

The determination of chromium (VI) compounds in plants by electrothermal atomic absorption spectrometry (ET AAS) is proposed based on their leaching with 0.1 M Na2CO3. Due to the presence of relatively high amounts of Na2CO3 in the resulting samples, the temperature and time of pyrolysis and atomization stages must be optimized to minimize the influence of the matrix. A limit of detection (LOD) for determination of Cr(VI) in plants by ET AAS was found to be 0.024 mu g g(-1). The concentration of Cr(VI) and total chromium in plants collected in different geographical areas (South Africa and Russia), grown on soils high in chromium was determined. The concentration of Cr(VI) and total Cr in stems and leaves of plants was in the range of 0.04-0.7 mu g g(-1) and 0.5-10 mu g g(-1), respectively.. The limited uptake of Cr(III) by plants, in comparison to its concentration in soil, can be explained by the very low solubility of natural Cr(III) compounds. Results for the determination of Cr(VI) were confirmed by the analysis of BCR CRM 545 (Cr(VI) in welding dust) with good agreement between certified (39.5 +/- 1.3 mu g mg(-1)) and found (38.8 +/- 1.2 mu g mg(-1)) values. The total concentration of Cr in plants has also been determined by ET AAS after dry ashing of samples at 650 degrees C. Results were confirmed by the analysis of BCR CRM 281 (Trace elements in Rye Grass) with good agreement between the found (2.12 +/- 0.16 mu g g(-1)) and certified value (2.14 +/- 0.12 mu g g(-1)). (c) 2005 Elsevier B.V. All rights reserved.