Potentiometric and chromatographic study of Cu(II) and Al(III) complexes of quercetin
Çıkla Yılmaz, Deniz
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In this study, the stability constants of the copper(II) and aluminium(III) complexes of quercetin were determined potentiometrically by using Calvin-Bjerrum and Irwing Rossotti methods. The protonation constants of quercetin were found: logK1 = 11.15±0.118, logK2 = 10.42±0.144, logK3 = 9.44±0.162, logK4 = 8.28±0.151. For copper complex formation constant was found by Irwing-Rossotti method: logK1 = 19.92±0.367 and for aluminium complex complex: logK1 = 23.02±0.459. From the results, the components of quercetin / metal complexes are given as 1/1 both copper(II) and aluminium(III). A reversed phase high pressure liquid chromatographic method was developed for the metal complexes which were prepared according to potentiometric results with the ratio quercetin / metal =1/1. Mobile phase was 0.01 M HClO4 / 8.33 x 10-5 M quercetin in Methanol (40/60), column was XTerra RP18, 5 μm, 4.6 x 150 mm , detector was Diode Array Detector at λ = 373 ve 421 nm (band width 4nm).