Determination of aluminum ion at ng mL^-1 level in natural water using trimethoxyphenylfl uorone by light-absorption ratio variation approach

The complexation between trimethoxyphenylfl uorone (TMPF) and Al ³⁺ is sensitive at pH 10.98 in the presence of both cetyltrimethylammonium bromide (CTAB) and acetone. CTAB was used as a sensitizer to bind TMPF and acetone as a stabilizer to inhibit the oxidation of the TMPF-Al complex. The masking reagent, ethylenediaminetetraacetic acid (EDTA) is helpful to improve the selectivity of the complexation. The spectral correction technique was applied to characterize the Al-TMPF complex and the formation of Al (TMPF)₂ complex. The light-absorption ratio variation approach (LARVA) is used for quantitative detection of Al³⁺ using complexation in a range from of 2 to 50 ng mL^-1 of Al3+. The lightabsorption ratio difference in this range is linear. The limit of detection (3σ) of Al³⁺ by the LARVA is only 2 ng mL^-1. Trace amounts of Al³⁺ in natural water has been determined with satisfactory results.