Spectrophotometric determination of acidity constant of Cinnamic acid using rank annihilation factor analysis (RAFA)

A significant parameter for understanding and quantifying chemical phenomena reaction rates, biological activity, biological uptake, biological transport and environmental fate [1] can be dissociation constants. In order to the determination of dissociation constants, several procedures such as potentiometric titration, spectrophotometric determination and conductometry, have been reported [2,3].Rank annihilation factor analysis (RAFA) was a means employed in order to determine spectrophotometrically the acidity constant of Cinnamic Acid in water at 25 °C and an ionic strength of 0.1 M. A general method in rank annihilation factor analysis (RAFA) is annihilation of the contribution of one chemical component from the original data matrix. The contributions HA were annihilated from the absorbance data After recording the electronic absorbance spectra of the acid at different pH, making possible the determination of successive acidity constant. It was obtained that there was a very close and exact agreement between the resulted values by RAFA(pKa=4.44 )and the declared values(pKa=4.44 ).