The Spectrophotometric and Fluorometric Determination of Aluminum with 8-Hydroxyquinoline and Butyl Acetate Extraction
1978
Bloom, P. R. | Weaver, R. M. | McBride, M. B.
A spectrophotometric method and a fluorometric method for the determination of Al by the extraction of the Al-hydroxyquinolate complex with butyl acetate were evaluated. The Al complex was found to be very stable in butyl acetate. Since butyl acetate is less dense than water the extractions could be done in screw top tubes and it was not necessary to dewater the solvent phase. The spectrophotometric method was found to be useful for the analysis of solutions containing 2 × 10⁻⁶M (50 ppb) Al or greater. The spectrophotometric response was linear up to absorbance = 1.1. The relative error in midrange was < 2.5%. The quantity of Al determined in soil extracts was shown for some soils to be strongly dependent on the time of contact with the complexing reagents before extraction with butyl acetate. This was attributed to the complexation of Al by organic matter in the soil solutions. The flourometric method was found to have a detection limit of about 1 × 10⁻⁸M (0.3 ppb) Al. The fluorometric response was nearly linear in the most sensitive range of the fluorometer but was less linear for higher Al concentrations. The relative error was < 8% except near the detection limit. There was no interference with either method from Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Fe²⁺, Fe³⁺, F⁻, PO₄³⁻, SO₄²⁻, and SiO₃²⁻ at the levels found in most soil extracts.
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