Determination of total cadmium in calcareous soils by extraction using aliquat‐336 and 3‐heptan‐one afteraqua regiadigestion
作者:
Y.‐M. Li,
L. Stanislavova,
R. L. Chaney,
期刊:
Communications in Soil Science and Plant Analysis
(Taylor Available online 1994)
卷期:
Volume 25,
issue 11-12
页码: 2029-2045
ISSN:0010-3624
年代: 1994
DOI:10.1080/00103629409369170
出版商: Taylor & Francis Group
数据来源: Taylor
摘要:
Measurement of total soil cadmium (Cd) is difficult due to calcium (Ca) and other chemicals which cause high background absorbance when trace levels of Cd are to be determined. When soil Cd is low, even use of deuterium background correction with flame atomic absorption spectroscopy (AAS) cannot provide accurate Cd results. Use of furnace atomic absorption with method of standard additions can circumvent these interferences, but the cost and time required are substantial. We desired a more rapid, convenient, and reliable alternative to extraction using dithizone and back‐extraction into acid, or to ammonium pyrollidinedithiocarbamate (APDC) which does not require close pH adjustment nor have many sources of potantial contamination. We evaluated analysis of these complex soil extracts with the method of Viets (1978) which extracts metals from 1N acid solutions using Aliquat‐336 in methylisobutyl‐ketone (MIBK). We tested the use of the less toxic and less water soluble 3‐heptanone as an organic solvent alternative to MIBK which can be directly analyzed by flame atomic absorption. A series of extraction experiments were conducted to determine if Cd was extracted from standard solutions and from total metal digests of calcareous soils into an Aliquat‐336/3‐heptanone solution, and under what conditions extraction was optimum. In the optimum method, Cd was extracted from aqua regia soil digests by 10% Aliquat‐336 in 3‐heptanone without addition of ascorbic acid or potassium iodide (KI) used by Viets. Excellent recovery of Cd was obtained for both standard reference soils and low Cd highly calcareous soils from North Dakota and Minnesota. Addition of ascorbic acid and KI did not increase the efficiency of extraction indicating that the extraction system used was free of ferric‐iron [Fe(III)] interference. The ion‐association complex of Cd remained stable for at least 24 hr after extraction, providing a very convenient method to analyze low levels of total Cd in soils and other geologic materials.
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