COMPARISON BETWEEN PYROCATECHOL VIOLET AND 8-HYDROXYQUINOLINE PROCEDURES FOR DETERMINING ALUMINUM FRACTIONS

There is currently considerable interest in quantifying concentrations of Al species in solution because of: (i) concern about the potential toxicity of inorganic forms of Al to plants and aquatic organisms, (ii) the need to better understand the processes contributing to soil development, and (iii) ongoing assessments of the biogeochemistry of Al. This study was conducted to compare the pyrocatechol violet (PCV) and 8-hydroxyquinoline (oxine) methods for the determination of monomeric Al fractions. A strongly acidic cation-exchange resin was used in automated PCV and nonautomated oxine procedures to separate aqueous Al into inorganic (labile) and organic (nonlabile) monomeric forms. Both synthetic and natural solutions were used in this analysis. Results showed good agreement between the two methods, suggesting that the PCV method is an acceptable alternative to the oxine method for the estimation of monomeric Al. In addition, the cation-exchange column fractionation procedure was verified using an F ion-selective electrode. Interference to the PCV method by Fe, F, and dissolved organic C was not significant across the range of solution concentrations studied.