Chemical Science International Journal

A very simple, ultra-sensitive and highly selective non-extractive spectrophotometric method is presented for the rapid determination of iron (III) at trace levels using ortho aminophenol or 2-aminophenol (OAP) as a new spectrophotometric reagent (l_max = 402 nm) in slightly acidic (0.0005-0.0015 M H₂SO₄) aqueous solution. The reaction is instantaneous and absorbance remains stable for over 24 h. The average molar absorption coefficient and Sandell’s sensitivity were found to be 6.65×105 L mol^-1 cm^-1 and 5 ng cm^-2, respectively. Linear calibration graphs were obtained for 0.01-6 mg L^-1 of iron with a correlation co-efficient value 0.9998 for Fe-OAP complex. The stoichiometric composition of the chelate is 1:3 (Fe: OAP). The detection limit and quantification of limit of the reaction system were found 1 µg L^-1 and 10 µg L^-1, respectively. Large excesses of over 50 cations, anions and complexing agents (e.g. tartrate, oxalate, citrate, phosphate, thio-urea, SCN^-) do not interfere in the determination. The developed method was successfully used in the determination of iron in several standard reference materials (alloys and steels) as well as in some environmental waters (portable and polluted), biological samples (human blood and urine), food samples (bean, meat, banana, tomato, egg etc.), soil samples, pharmaceutical samples (tablets, capsules etc.), some solution containing both iron (II) and iron (III) and complex synthetic mixtures. The results of the proposed method for biological and food samples were comparable with AAS and were found to be in excellent agreement. The method has high precision and accuracy (s = ±0.01 for 0.5 mg L^-1).