In 1988, Bosch-Reig and Compais-Falco [1] presented a new technique H-point standard addition method (HPSAM), that was based on the principle of dual wavelength spectrophotometer and the standard addition method. The greatest advantage of HPSAM is that it can remove the errors resulting from the presence of an interfering and blank reagent. So, HPSAM can determine the two components simultaneously [2-4]. In this work, a kinetic model has been constructed to investigate the possibility of the simultaneous of Fe (II) and Fe (III) or selective determination of Fe (III) in the presence of Fe (II) by using HPSAM. The method was based on the difference in the rate of two processes ; reduction of Fe(II) whit cystein and subsequent complex formation whit 1,10-phenanthrolin ,and direct complex formation between Fe(II) and 1 ,10-phenanthrolin. The optimum conditions, for Simultaneous Kinetic-determination of Fe (II) and Fe (III), Such as 1, 10-phenanthrolin concentration, cystein concentration, pH, temperature, and ionic strength were investigated. The calibration curve was linear in the range of 0.2 µg/ml to 4 µg/ml for Fe (II) and Fe (III), both. Relative standard deviation for five replicate analysis of 1 µg/ml Fe (II) and 1 µg/ml Fe (III) were obtained 3% and 2%, respectively. The effects of interferences also were investigated. The proposed method was successfully applied for the determination of Fe (II) and Fe (III) in the drinking water.

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