Selective Spectrophotometric Determination of Aluminium in the Presence of Beryllium and Lanthanide Cations

Abstract.

A spectrophotometric method for the selective determination of Al(III) in the presence of Be and Ln (lanthanide) cations is proposed. It is based on the selective reaction of SXO (Semi-Xylenol Orange) with Al(III) at pH 2.6. The presence of 8% v/v of 1,2-ethanediol serves to stabilize the chelate formed by heating at 100 °C for 5 min. 0.5 mg each of Be(II), Ce(III), La(III), 4 mg of Mn(II), 1.2 mg of Pb(II), 1 mg of Tl(I), 40 mg each of Ca(II) and Mg(II) and 1.9 mg of sodium dihydrogen phosphate are tolerable. A ligand buffer of HEDTA-Pb is incorporated to further enhance the selectivity of the color reaction. Under the specified conditions SXO reacts with Al(III) to form a 1:1 chelate. Its molar absorptivity at 526 nm was found to be 3.3×10⁴ L mol⁻¹ cm⁻¹. The linear regression equation for 2–20 µg of Al(III) is A=0.04458C+0.0112 (where C stands for the concentration of Al(III), µg per 25 mL) and correlation coefficient γ=0.9988. The RSD at the level of 10 µg (n=10) and LOQ were found to be 3.5% and 2 µg, respectively.