A spectrophotometric investigation of the complex between titanyl oxalate and 3-hydroxyflavone in water ethanolic mixtures

Abstract

It has been established, by the application of suitable spectrophotometric methods and pH-metric measurements, that titanyl oxalate anion and 3-hydroxyflavone (3HF) form a [TiO(C2O4)2(C15H9O3)2]4- complex. The investigation of the composition and the concentration stability constant of the complex were carried out in a 50 % aqueous ethanol solution at room temperature (20 °C), in the pH range from 1.9 to 9.0. The concentration stability constant of the complex, log β2, ranged from 16.65 at pH 5.0 to 13.96 at pH 7.0. The conditions for the spectrophotometric determination of 3HF by means of the complex formation were investigated in the concentration range from 2.5 x 10-5 to 3.0 x 10-4 mol dm-3 3HF.

Korišćenjem pogodnih spektrofotometrijskih i pH-metrijskih metoda utvrđeno je da titanil oksalat i 3-hidroksiflavon (3HF) grade [TiO(C2O4)2(C15H9O3)2]4- kompleks. Ispitivanje sastava i određivanje koncentracionih konstanti stabilnosti ovog kompleksa vršeno je u 50 % etanolnom rastvoru, na sobnoj temperaturi (20 °C), u oblasti pH od 1,9 do 9,0. Izračunate vrednosti koncentracione konstante stabilnosti kompleksa, log β2, su u intervalu od 16,65 pri pH 5,0 do 13,96 na pH 7,0. Određeni su i uslovi za spektrofotometrijsko određivanje 3HF korišćenjem nagrađenog kompleksa u koncentracionom intervalu od 2,5 x 10-5 do 3,0 x 10-4 mol dm-3.