Determination of Trace Fe(III) by Catalytic Kinetic Spectrophotometry

A new system was investigated for the determination of trace Fe(Ⅲ) with the kinetic spectrophotometric method in this paper. Buffer medium is hydrochloric acid-adjacent benzene hydrogen potassium solution(pH= 2.2). In this paper it has been found that the trace Fe( Ⅲ) can catalyze the oxidation of the O-methoxyphenol. The optimum condition and dynamic parameter were studied. The reaction mechanism of this reaction system was discussed. A new kinetic spectrophotometric method for the determination of trace Fe(Ⅲ) was developed. The selectivity of the method is relatively high. Many foreign ions don't interfere with the determination of Fe( Ⅲ ). The linear range is 0.07-1.1 μg·(25 mL)-1 . A detection limit of 5.4×10-8 g·L-1 was achieved. The measurement of trace Fe(Ⅲ) was applied to river water sample, tap water sample, city sewage sample, soybean milk powder sample and tea sample. The relative standard deviations(RSD) were between 0.36%-3.4% , and the recoveries were 97.3%-102.7% . The results of determination for these actual samples are satisfactory.