A simple spectrophotometric method for the determination of iron(II) aqueous solutions


Abstract: An ultra-sensitive and highly selective non-extractive spectrophotometric method is presented for the rapid determination of iron(II) at trace levels using 2', 3, 4', 5, 7-Pentahydroxyflavone (morin) as a new spectrophotometric reagent in slightly acidic solution (0.0001-0.0002 M H_2SO_4). The reaction is instantaneous and absorbance remains stable for over 24 h (\lambda_{max} = 415 nm). The molar absorptivity was found to be 6.85 \times 10^4 L mol^{-1} cm^{-1}. Linear calibration graphs were obtained for 0.01-10 \mu g mL^{-1} of Fe^{II}. The stoichiometric composition of the chelate is 1:2 (Fe:morin). 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 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 (arum, apple, egg, etc.), soil samples, and some complex synthetic mixtures. The method has high precision and accuracy [s = \pm 0.001 for 0.5 \mu g L^{-1} (n = 5)] over 24 h; 415 nm was used.

Keywords: Spectrophotometry; iron determination; morin; alloys; steels; environmental; biological samples; soil samples.

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