Photometric Determination of Traces of Iron(Ⅲ) Based on Its Catalytic Action on Oxidation of Guaiacol by Potassium Periodate

In a phthalate buffer medium of pH 2.6 and in the presence of o-phenanthroline as activator, catalytic action of Fe(Ⅲ) on the oxidation of guaiacol by KIO4 was studied and its kinetic parameters were tested. The reaction mixtures in two 25 mL volumetric flasks containing in one flask 0.30 mol·L-1 guaiacol solution 0.6 mL, phthalate buffer solution 1.5 mL, 1×10-3mol·L-1 o-phenanthroline solution 2 mL, 0.03 mol·L-1 KIO4 solution 3 mL and a definite amount of Fe(Ⅲ), and in the another flask the same reagents but without Fe(Ⅲ), were heated after diluting to 25 mL in a water bath at 60 ℃±0.5 ℃ for 6 min. The values of absorbance of both solutions were taken at the wavelength of 480 nm and ΔA was calculated by A-A0. Linear relationship between values of ΔA and mass concentration of Fe(Ⅲ) was kept in the range of 0.2-2.0 μg·L-1, with detection limit (3S/N) of 2.3×10-2μg·L-1. Samples of pure water, mineral water, grape wine and beer were analyzed by this method for their Fe(Ⅲ) contents, the results obtained were in conformity with the results found by FAAS, and values of RSD′s (n=6) found were in the range of 0.51%-2.1%.