A simple and rapid spectrophotometric method for the determination of iron in environmental, biological, pharmaceutical, food and soil samples using 1,2-dihydroxybenzene-3,5-disulfonic acid

Abstract

An ultra-sensitive and highly selective non-extractive spectrophotometric method is presented for the rapid determination of iron (III) at trace levels using 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) as a new spectrophotometric reagent (l_max = 665 nm) in slightly acidic aqueous (2×10^-6 - 2×10^-5 mol/L H₂SO₄) solution. The reaction is instantaneous and absorbance remains stable for over 24 h. The average molar absorption coefficient and Sandell’s sensitivity and detection limit were found to be 6.0×10⁵ L/mol.cm, 10 ng/cm², and 1 µg/L, respectively. Linear calibration graphs were obtained for 0.02-70.00 mg/L of Fe(III). The stoichiometric composition of the chelate is 2:3 (Fe(III):Tiron). Large excesses of over 50 cations, anions and complexing agents (e.g. Tartrate, oxalate, citrate, phosphate, thiourea, and thiocyanate) do not interfere in the determination. The 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, pharmaceutical and soil samples, solution containing iron (II) and iron (III) and some complex synthetic mixtures. The method has high precision and accuracy (s = ±0.01 for 0.5 mg/L).