Spectrophotometric determination of traces of iron(II) with novel water-soluble nitrosophenol derivatives

Abstract

Eight water-soluble derivatives of nitrosophenol were synthesized and their analytical applications have been investigated. The reagents were prepared through the N-sulfoalkylation of N-alkyl-m-aminophenols with propanesultone, 2-bromoethanesulfonic acid, or 3-chloro-2-hydroxypropanesulfonic acid, followed by the nitrosation with butyl nitrite. They are yellow to brown crystalline powder and very soluble in water. The acidic aqueous solutions are stable at least in one month. Each reagent reacts with iron (II) to form an intense green, water-soluble complex in a wide range of acidity (weakly acidic to alkaline). Among the reagents obtained 2-nitroso-5-(N-propyl-N-sulfopropylamino) phenol (Nitroso-PSAP) having 4.5×104 dm3 mol−1 cm−1 of molar absorptivity at 756 nm was most sensitive. The composition of the iron(II) complex was found to be 1: 4 (Fe:reagent) by molar ratio method. To a sample solution (containing up to 25µg of iron), 2 ml of 0.1 M solution of ascorbic acid, 5 ml of 1×10−3 M solution of Nitroso-PSAP in 0.1 M hydrochloric acid, and 5 ml of 2 M solution of ammonium acetate were added and then diluted to 50 ml with water. The absorbance at 756 nm was measured against a reagent blank. Beer's law was obeyed from 2×10−7 M to 1×10−4 M of iron. The coefficient of variation for five determinations was 1.2 % for 1×10−5 M of iron. Equimolar amounts of Cu(II), Co(II), Ni(II), Zn(II), Cd(II), Al(III), and Ca(II) did not interefere. © 1981, The Japan Society for Analytical Chemistry. All rights reserved.