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A new spectrophotometric method for fluoride based on its bleaching action on the color of aluminium (III) -gallacetophenone phenylhydrazone complex

D.Venkataramana Reddy, P.Jeevan Jyothi

A simple, sensitive, rapid and economical spectrophotometric method for the determination of fluoride is developed. The method is based on the bleaching action of fluoride on the intense yellow colour ofAl (III)-GPPH complex with proportional decrease of absorbance. Therefore, in principle the decrease in colour intensity of the absorbing medium is proportional to the concentration of fluoride.At first, aluminiumis determined spectrophotometrically by measuring the absorbance at 375nm. The system obeyed Beer’s lawupto 2.0ppmofAl. Themolar absorptivity and Sandell’s sensitivity of theAl (III) -GPPHcomplex are 1.341041.mole-1cm-1. and 0.002g cm- 2 respectively. The stoichiometry of the complex is found to be 1:1 by both Job’s continuous variation and molar ratio methods. The stability constant of the complex is 3.197103 at 30C. The effect of diverse ions has been studied. Based on the above principle, the method is employed for the determination of fluoride in water samples. The results of the proposed method are in close agreement with the values obtained fromAAS.