SOLOCHROME YELLOW 2GS AS ORGANIC REAGENT FOR SPECTROMETRIC DETERMINATION OF IRON(III)

A rapid, reliable and inexpensive method for the direct determination of Fe (111) with the organic reagent Solochrome Yellow 2GS (disodium salt of 2-hydroxy-5-[(4-sulfophenyl)azo]-benzoic acid) is reported. In a 5-fold excess over Fe (111) concentration the organic reagent, R form with Fe (111) within pH range 2.79-3.00 a 1:2 (Fe:R) stable complex. The value of the total stability constant beta(s) = 3.023.10(5) +/- 1.55.10(5) L(2).mol(-2) was determined, which indicates the formation of a rather stable complex. On this basis a spectrometric method for the quantitative determination of traces of iron (111) was proposed. The method is sensitive, accurate and reproducible, being characterized by a detection limit of 0.11 mg.L(-1), a linearity range between 0.3-5.0 mu g.mL(-1), a recovery of 98.45% +/- 1.38%, as well as a good repeatability and reproducibility, characterized by relative standard deviations of 1.537% and 1.365%, respectively. This method was applied in order to determine the iron contents in samples of drinking water and natural mineral water.