Trace determination of iron in natural products

A new organic reagent, (E)-2-hydroxy-3-((2-hydroxybenzylidene) (amino) benzenesulphonic acid, was synthesised on the basis of salicylic aldehyde. The complexation of iron (III) with c (E)-2-hydroxy-3-(2-hydroxybenzylidene) (amino) benzenesulphonic acid (R) was studied both in the presence and absence of the following surface-active substances (SAA): cetylpyridinium chloride, cetyltrimethylammonium bromide and Triton X-114. Fe (III) was established as forming coloured mixed-ligand complexes with the reagent in the presence of third components. The optimal complexation conditions were determined for the Fe (III)-R binary complex (pH = 4, lambda(max) = 353 nm), as well as for the multi-ligand complexes of Fe(III)-R-CPCI (pH = 3, lambda(max) = 374 nm), Fe(III)-R-CPMABr (pH = 2, lambda(max) = 392 nm) and Fe(III)-R-Triton X-114 (pH = 3, lambda(max) = 385 nm). The proportion of reacting components in the composition of Fe(III)-R homogeneous ligand iron compounds was determined to be equal to 1:2. Mixed ligand compositions were 1:1:2, 1:1:1 and 1:2:1 for Fe (III)-R-CPCI, Fe(III)-R-CPMABr and Fe(III)-R-Triton X-114, respectively. The molar absorption coefficients and stability constants of Fe(III) complexes were determined. The molar coefficients of the complexes Fe(III)-R, Fe(III)-R-CPCI, Fe(III)-R-CPMABr and Fe(III)-R-Triton X-114 comprise 10,000, 16,250, 19,000 and 11,000, respectively. The intervals of obedience to Beer's law (mu g/mL) were determined to range 0.448-2.24, 0.112-4.48, 0.12-4.48 and 0.224-2.24 for Fe(III)-R, Fe(III)-R-CPCI, Fe(III)-R-CPMABr and Fe(III)-R-Triton X-114, respectively. The effect of some ions and masking substances on the formation of binary and mixed-ligand complexes of Fe(III) was studied. The presence of a surfactant was demonstrated to significantly increase the selectivity of the reaction. A technique was developed for spectrophotometric determination of Fe(III) in beans, mushrooms and briar. The data obtained using the proposed method are in good agreement with the results of atomic absorption spectrometry. The proposed method for the determination of Fe(III) with (E)-2-hydroxy-3-(2-hydroxybenzylidene)(amino)benzenesulphonic acid in the presence of cetyltrimethylammonium bromide (CTMABr) is simple, rapid and provides reliable results.