Abstract: In this study, the stability constants of the complexes of quercetin formed
with aluminium(III) and iron(II) were determined potentiometrically by using
Calvin-Bjerrum and Irving Rossotti methods and by spectrophotometric way. The
evaluated protonation constants of the ligand were found: logK1=9.630.11and
logK2 = 8.32013, at the 25°C. For the aluminium and iron complexes logarithms of
the stability constants were found: for Al : logK1=14.050.09 , logK2=10.020.12,
and for Iron: logK1=9.440.11, logK2=3.860.08.
Key words:quercetin, aluminium, iron, stability constant, potentiometri,