Extraction-photometric determination of iron using 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl] naphthalen-2-ol

The interaction of iron ions with 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol and 1-[(5-(4-methoxybenzyl)-1,3-thiazol-2-yl)diazenyl]-naphthalen-2-ol was studied by spectrophotometric method. It was proved that Fe 3+ ions do not interact with the indicated reagents. The addition of Fe 2+ ions to solutions of 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol and 1-[(5-(4-methoxybenzyl)-1,3-thiazol-2-yl)diazenyl]-naphthalen-2-ol leads to significant changes in the light absorption spectra of the reagents. This indicates the formation of complex compounds of 1,3 thiazole derivatives with Fe(II) ions. Complex compounds exist in a narrow range of acidity of media. The pH limits of the existence of the complex of iron with 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol are somewhat higher compared to 1-[(5-(4-methoxybenzyl)-1,3-thiazol-2-yl)diazenyl]-naphthalen-2-ol. It has been proven that the interaction between Fe 2+ ions and 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol occurs in a stoichiometric ratio of 1:2. Since the complex compound Fe(II) with 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol in aqueous-ethanol solutions turned out to be unstable over time, and chloroform quantitatively extracts the complex, an extraction-photometric method for the determination of iron was developed. Chemical-metrological characteristics of the developed method: λ max 800 nm; ε – 1.20×10 4 l×mol -1 ×cm -1 ; concentration interval 2.0 ÷ 10.0 μmol/l; detection limit – 0.75 μmol/l). The selectivity of the new extraction-photometric method was investigated. The determination of iron is not interfered with by ions of alkali and alkaline earth metals and ions Pb 2+ and Al 3+ . The determination is hindered by more than tenfold excesses of Co 2+ , Cd 2+ , and Zn 2+ ions and comparable amounts of Cu 2+ and Ni 2+ . The new method has been tested in the analysis of real objects – natural field soils. Keywords: 1-[(5-(4-methylbenzyl)-1,3-thiazol-2-yl)diazenyl]naphthalen-2-ol, spectrophotometry, iron, 1,3-thiazoles, azodyes.