The analysis of iron(III) using solvent extraction with phenylacetic and n-decanoic acids

The extraction of Fe(III) from aqueous solutions by phenylacetic acid in chloroform solution provides a simple, rapid, and accurate method for the determination of low amounts of iron. Concentrations less than 1 μg/ml can be easily determined particularly if advantage is taken of the amplification procedure afforded by the solvent extraction technique by using a large aqueous to organic phase ratio. A maximum concentration of iron(III) of about 18 μg/ml in the aqueous phase (aqueous to organic phase ratio of 2.5:1) can be determined; however, above this concentration deviations from Beer's Law occur for the absorbance of the organic phase. The method is very selective, particularly in the presence of copper, provided care is taken to adjust the aqueous pH to a value of 2.8. n -Decanoic acid could also be used in the method in place of phenylacetic acid and would have some advantage in selectivity, particularly in cases where very large amounts of Ag(I) and Pb(II) were present.