Ascorbic acid is responsible for reducing all the Fe(III) to Fe(II) form in aqueous phase. The amount of ascorbic acid must be enough and do not bring about interference. The influence of ascorbic acid concentration was investigated by varying volumes of 5 103 mol in the range of 0.3–2 mL. The maximum absorbance was obtained in the range of 0.3–1.0 mL. Hence,1.0 mL of 5 103 mol L1 ascorbic acid was used for the further experiments.