Some characteristics of apigenin-aluminum complex in alcohol-water solutions

Abstract

Basic studies were made of the spectrophotometric determination of aluminum using apigenin (5, 7, 4'- trihydroxyflavone), which had been proposed as a possible reagent by Nowicka-Jankowska et al. Chem. Anal. (Warsaw), 10, 129 (1965). Experimental emphases were put on the measurements of the maximum absorption wavelength, the optimum pH-value, the molar composition, the molar absorptivity and the stability of apigenin-aluminum complex in 50% (v/v) alcoholic medium.Preceding experiments confirmed that ethanol was unsuitable as a solvent for the complex formation, and revealed also that the acetate-buffer-solution interferred (Fig. 1). The following results were thus obtained in 50% (v/v) methanolic media, the pH of which was adjusted with a dilute sodium hydroxide solution or with dilute hydrochloric acid;(1) the maximum absorption wavelength; 388 nm(2) the optimum pH value; 5.1 (Fig. 2)(3) the molar composition; Al (apigenin)2 (Fig. 3)(4) the molar absorptivity; 26400 (388 nm, pH 5.1)(5) the stability of the complex; No change of absorbance was observed even on keeping it for 24 hours at room temperature.(6) The disadvantage of this reagent is the sensitive dependence of the absorbance of the complex on pH. (Fig. 2)