Limitations of acid digestion techniques for the determination of fluoride in plant material
Date
1995
Authors
Stevens, D.
McLaughlin, M.
Alston, A.
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Journal article
Citation
Communications in Soil Science and Plant Analysis, 1995; 26(11-12):1823-1842
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Abstract
Procedures for determination of fluoride (F) in plant material employing acid digestion and solution analysis by ion specific electrode (ISE) were compared to alkali fusion using a range of plant materials. The efficiency of the methods were assessed using standard reference plant material (SRM) not previously available for plant F analysis. All acid digestion procedures tested failed to obtain the certified value for F in the SRM. This was due to failure of the acids to liberate F bound strongly within silicate minerals found in the plant materials. Acid digestion is therefore not recommended for determination of total F, but could be used to determine labile F in plant materials. During investigation of the acid digestion procedures, it was also found that F concentrations determined in solution using the ISE are sensitive to solution pH, even at solution pH values where complexation of F with hydrogen ions (H⁺) can be discounted. It is therefore recommended that both ionic strength and pH of sample and standard solutions be matched when determining F concentrations in solution using the F-ISE.