Quantitative Analysis of Elements in Sediments and Soils by X-Ray Fluorescence

Abstract

Abstrac~Previous applications of the method of known additions for quantitative X-ray fluorescent analysis have assumed a linear relationship between peak intensity and concentration of the element being analyzed. This assumption is true for soils or sediments containing small amounts of the element in question. In this paper, an equation is derived which takes into account both absorption and enhancement and thus is applicable to samples containing high concentrations of the element. The equation was tested by analyzing an artificial soil sample containing 60% kaolinite and 40% hematite, i.e. the sample contained 28% by weight iron. The fluorescent analysis utilizing the equation derived here resulted in an iron content of 27%. In addition, nine soils from Hawaii were analyzed by this method and the results of these analyses compared with analyses by atomic absorption. The agreement between the two methods is good. It is concluded that the method and equations proposed here provides a reliable measurement of elements in a soil sample which contains high concentrations of the elements in question.

Quantitative Analysis of Elements in Sediments and Soils by X-Ray Fluorescence: A Reply

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Since the references cited in Tuncer et al (1977) address many of the points raised by Subramanian (1979), e.g., Diehl (1970) for the determination of iron in earth materials, we do not feel obliged to elaborate on all of his comments. However, his remarks on grain-size distribution which directly influences the homogeneity of a sample deserve special attention.

For the sake of brevity the method of sample preparation used in the original experiments was not outlined in detail in the 1977 paper; however, all of the materials used were ground to pass a 200 mesh sieve to assure a maximum composite particle size of less than 75/~m, which was considered satisfactory for achieving homogeneity for relatively strong iron radiation.

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“…Since the references cited in Tuncer et al (1977) address many of the points raised by Subramanian (1979), e.g., Diehl (1970) for the determination of iron in earth materials, we do not feel obliged to elaborate on all of his comments. However, his remarks on grain-size distribution which directly influences the homogeneity of a sample deserve special attention.…”

Quantitative Analysis of Elements in Sediments and Soils by X-Ray Fluorescence: A Discussion

“…In a recent issue of this journal, Tuncer et al (1977) described a mathematical treatment of X-ray fluorescence (XRF) data to estimate the elemental composition of soils. The following discussion refers to this paper: Tuncer et al (1977) compared results obtained by three analytical techniques; however, their methodology for preparing samples for atomic absorption spectrophotometry (AA) indicates that an undisclosed amount of "insoluble residue" was removed from the solution prior to analysis.…”

“…The following discussion refers to this paper: Tuncer et al (1977) compared results obtained by three analytical techniques; however, their methodology for preparing samples for atomic absorption spectrophotometry (AA) indicates that an undisclosed amount of "insoluble residue" was removed from the solution prior to analysis. The soils analyzed by XRF, on the other hand, contained this material as one of their components, with resultant matrix problems.…”

“…Further, it is difficult to calculate exactly the mass absorption coefficient of the matrix for soil without knowing its chemical composition. Tuncer et al (1977) used the internal standard technique only for iron determinations. The suitability of the equations developed by them for the analysis of other elements by XRF method remains to be verified experimentally.…”