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This article in SSSAJ

  1. Vol. 53 No. 1, p. 38-44
     
    Received: Mar 22, 1988


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doi:10.2136/sssaj1989.03615995005300010008x

Evaluation of Three Aluminum Assay Techniques for Excluding Aluminum Complexed with Fluoride or Sulfate

  1. A. K. Alva ,
  2. M. E. Sumner,
  3. W. P. Miller and
  4. Y. C. Li
  1. Dep. of Agronomy, Coastal Plain Exp. Stn., P.O. Box 748, Tifton, GA 31793-0748
    Dep. of Agronomy, Univ. of Georgia, Athens, GA 30602
    Shandong Cotton Research Center, Jinan City, People's Republic of China

Abstract

Abstract

Aluminon, 8-hydroxyquinoline and ferron reagents are often used to measure Al in solutions. Since Al complexed with F- or SO2-4 is less phytotoxic, in solutions containing these ligands an estimate of Al excluding that complexed with F- and/or SO2-4 represents predominantly phytotoxic Al. In the present study, the capacity of the above reagents to exclude Al complexed with F- or SO2-4 was evaluated in solutions containing 40 µM Al with 20 to 640 µM F- or 40 to 5120 µM SO2-4 at pH 4.5. The effects of varying reaction time from 15 s to 30 min on the recovery of Al by the respective reagents was also investigated. The sum of predicted (by MINTEQ speciation model) concentrations of Al3+ and hydroxy-Al monomers decreased to 45% or to 0.6% of total Al in solutions with 5120 µM SO2-4 or 80 µM F-. The concentration of Al measured by 8-hydroxyquinoline (15- or 60-s reaction) or aluminon (15-s reaction) appeared to exclude entirely Al complexed with F-. All three reagents, however, regardless of reaction time, failed to exclude Al complexed with SO2-4. Therefore, 8-hydroxyquinoline (15- or 60-s reaction) aluminon (15-s reaction) reactive Al would accurately represent phytotoxic Al in the presence of F-, while ferron reagent is likely to overestimate the phytotoxic Al. In the presence of SO2-4, however, all three reagents are likely to overestimate the phytotoxic Al.

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