Spectrophotometric study of iron oxidation in the iron(II)/thiocyanate/acetone system and some analytical applications

The possibility of using thiocyanate to determine iron(II) and/or iron(III) in water-acetone mixture has been re-examined as part of a systematic and comparative study involving metallic complexes of pseudohalide ligands. Some parameters that affect the complete oxidation of the ferrous cations, their subsequent complexation and the system stability have been studied to optimize the experimental conditions. Our results show the viability and potentiality of this simply methodology as an alternative analytical procedure to determine iron cations with high sensitivity, precision and accuracy. Studies on the calibration, stability, precision, and effect of various different ions have been carried out by using absorbance values measured at 480 nm. The analytical curve for the total iron determination obeys Beer's law (r = 0.9993), showing a higher sensitivity (molar absorptivity of 2.10x10 4 L cm -1 mol -1 ) when compared with other traditional systems (ligands) or even with the "similar" azide ion (1.53x10 4 L cm -1 mol -1 , for iron-III/azide complexes, in 70% (v/v) tetrahydrofuran/water, at 396 nm). Under such optimized experimental conditions, it is possible to determine iron in the concentration range from 0.5 to 2 ppm (15-65% T for older equipments, quartz cells of 1.00 cm). Analytical applications have been tested for some different materials (iron ores), also including pharmaceutical products for anemia, and results were compared with atomic absorption determinations. Very good agreement was obtained with these two different techniques, showing the potential of the present experimental conditions for the total iron spectrophotometric determinations (errors < 5%). The possibility of iron speciation was made evident by using another specific and auxiliary method for iron(II) or (III).

[1]  F. Albert Cotton,et al.  Advanced Inorganic Chemistry: A Comprehensive Text , 1972 .

[2]  J. F. Andrade,et al.  Potentiometric study of azide complexes of iron(III) in aqueous medium , 1986 .

[3]  Orliney Maciel Guimarães,et al.  Spectrophotometric study of iron oxidation in the iron(II)/azide/tetrahydrofuran system and some analytical applications , 2000 .

[4]  Orliney Maciel Guimarães,et al.  Spectrophotometric Determination of Uranium Through Uranyl/Azide System , 1995 .

[5]  S. Mannino,et al.  Application of adsorptive stripping voltammetry to the speciation and determination of iron(III) and total iron in wines. , 1989, The Analyst.

[6]  L. Stookey.  Ferrozine---a new spectrophotometric reagent for iron , 1970 .

[7]  S. M. Sultan,et al.  A study of the formation and stability of the iron(III)-thiocyanate complex in acidic media , 1982 .

[8]  M. Worwood.  The laboratory assessment of iron status--an update. , 1997, Clinica chimica acta; international journal of clinical chemistry.

[9]  M. Hoffmann,et al.  Simultaneous spectrophotometric measurement of iron(II) and iron(III) in atmospheric water , 1992 .

[10]  P Carter,et al.  Spectrophotometric determination of serum iron at the submicrogram level with a new reagent (ferrozine). , 1971, Analytical biochemistry.

[11]  G. Chierice,et al.  Simultaneous spectrophotometric determination of copper(II) and iron(III) as the azide complexes , 1983 .

[12]  K. Johnson,et al.  Determination of subnanomolar levels of iron(II) and total dissolved iron in seawater by flow injection and analysis with chemiluminescence detection , 1991 .

[13]  J. F. Andrade,et al.  Spectrophotometric determination of iron (III) as azide complexes in aqueous tetrahydrofuran , 1987 .

[14]  Ana Paula Cabral Sader.  "Estudo espectrofotométrico do sistema cobalto(II)/tiocianato e seu aproveitamento analítico" , 2002 .

[15]  Adriana de Azevedo Paiva,et al.  Parâmetros para avaliação do estado nutricional de ferro , 2000 .

[16]  M. Aihara,et al.  Determination of iron(II) and total iron in environmental water samples by flow injection analysis with column preconcentration of chelating resin functionalized with N-hydroxyethylethylenediamine ligands and chemiluminescence detection. , 1999, Talanta.

[17]  G. Kaufman.  Inorganic chemistry: principles of structure and reactivity, 4th ed. (Huheey, James E.; Keiter, Ellen A.; Keiter, Richard L.) , 1993 .

[18]  G. Chierice,et al.  Spectrophotometric Determination of Copper(II) as the Azide Complexes, in the Presence of Iron(III) Cations , 1985 .

[19]  Orliney Maciel Guimarães,et al.  Spectrophotometric Determination of Sulfate Ion Through Copper(II)-azide System , 1993 .

[20]  M. Anke,et al.  Elements and their compounds in the environment , 2004 .

[21]  G. Chierice,et al.  The stepwise formation of complexes in the uranyl/azide system in aqueous medium , 1983 .

[22]  N. Coichev,et al.  The stepwise complex formation in the cobalt(III)-azide system , 1989 .

[23]  P. Gareil,et al.  Direct determination of iron(II), iron(III) and total iron as UV-absorbing complexes by capillary electrophoresis , 1996 .