KINETIC-POTENTIOMETRIC DETERMINATION OF FE(III) USING A FLUORIDE ION-SELECTIVE ELECTRODE

A kinetic-potentiometric method is described for the determination of Fe(III), based on monitoring of the formation or FeF2+ in acid solution, using a fluoride ion-selective electrode. The influence of pH and fluoride concentration in cell solution on the kinetics of iron - fluoride reaction was studied. The initial rate of the complex formation reaction, or change in potential during fixed time interval (1 minute), was used to construct calibration graphs. There is a linear relationship between the calculated initial rate or (DELTA-E)1min and the concentration of iron in the cell solution. Good linearity (r = 0.9979) was achieved in the range of iron concentration from 3.5 x 10(-5) M to 1.4 x 10(-3) M.