"Estudo espectrofotométrico do sistema crômio(III)/azoteto e seu aproveitamento analítico".

Lourenço, Leandro Maranghetti

doi:10.11606/d.59.2004.tde-20032004-145858

Cited by 4 publications

(5 citation statements)

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“…Under the best acid and ligand concentrations, the maximum absorption occurs at 287 nm, being this band more sensitive than the visible one located between 400 and 700 nm, which was used in the work of Sherif and Orab [14]. It has also been noticed [16] that, although the azide ligand also absorbs in the ultraviolet region, such absorption is limited to areas around 230 nm (under the present conditions). The absorption of azide at 287 nm is weak, thus allowing spectrophotometric measurements for the chromium(III)/azide system at low concentrations in the ultraviolet region.…”

Section: Resultsmentioning

confidence: 56%

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Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

Lourenço¹,

Martins²,

Balbo³

et al. 2006

Eclet. Quím.

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IntroductionAzide and thiocyanate complexes of several metallic cations have been systematically studied in our laboratories with a view to understanding their coordination chemistry (equilibria) [1][2][3] and developing their analytical applications [4][5][6][7][8][9][10][11][12]. There is great analogy between the azide and the thiocyanate ligands (pseudohalides), since they develop the same red color in acid solution containing iron(III). Some of our studies have been of a comparative character, showing that the azide system is much more stable than the thiocyanate one. As part of these continuous investigations, it is expected that chromium(III) will form complexes with the pseudohalide azide in the same way that other transition metals such as iron, copper, nickel, and cobalt.In the literature, studies carried out by Sherif and Orab [13,14] in aqueous medium using the visible region revealed the existence of a relationship between the several free ligand (azide) and chromium(III) concentrations with absorbance, producing colorings ranging from violet to green. Moreover, the solution was reported to develop blue tones under great ligand excess. In the work of Templeton & King [15], the effect of perchloric acid concentration on the formation of pentaaquoazidochromium(III) compounds was also reported. The main objective of the latter work was to determine the kinetics and equilibrium of this system. The authors reported maximum absorption at 270 nm, under highly acid concentrations, which was attributed to interactions between azidochromium(III) and/or hydrogen azidochromium(III) and the perchlorate ion. The Abstract: A sensitive and alternative method for the spectrophotometric determination of chromium(III) based on the formation of chromium(III)/azide complexes was established by investigating a new band in the ultraviolet region. The best experimental conditions for the analytical determination of this metallic ion were: ligand and perchloric acid analytical concentration = 493 and 12.0 mmol L -1 , respectively; aqueous medium; T = 25.0 ºC; contact time = 1 hour. The maximum molar absorptivity coefficient occurred at 287 nm (average 1.481 ± 0.008 × 10 4 L mol -1 cm -1 ), leading to the determination of metal ion concentrations one hundred times lower than the ones formerly determined in the visible region. The system obeys Beer's Law and is suitable for chromium determination in the 0.702-2.81 mg L -1 concentration range (15-65% T, 1.00 cm-width quartz cells).Analytical applications of the current method were tested with a nutritional supplement containing chromium. Results were compared with those obtained with atomic absorption spectrometry.

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Section: Resultsmentioning

confidence: 56%

“…After this optimization [16], it was possible to notice that the same conditions considered ideal in the visible region could be employed in the ultraviolet region, leading to the determination of metal ion concentrations a hundred times lower than the ones determined in the former region.…”

Section: Resultsmentioning

confidence: 99%

Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

Lourenço¹,

Martins²,

Balbo³

et al. 2006

Eclet. Quím.

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“…Measurements at 287 nm were only carried out in this work after optimization of the conditions previously used by Sherif [13] in the visible region, when factors such as acidity, ligand concentration, nature and concentration of solvent, temperature and contact time were investigated too. After this optimization [16], it was possible to notice that the same conditions considered ideal in the visible region could be employed in the ultraviolet region, leading to the determination of metal ion concentrations a hundred times lower than the ones determined in the former region.…”

Section: Resultsmentioning

confidence: 99%

Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

et al. 2006

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A sensitive and alternative method for the spectrophotometric determination ofchromium(III) based on the formation of chromium(III)/azide complexes was established byinvestigating a new band in the ultraviolet region. The best experimental conditions for the analyticaldetermination of this metallic ion were: ligand and perchloric acid analytical concentration = 493 and12.0 mmol L -1 , respectively; aqueous medium; T = 25.0 oC; contact time = 1 hour. The maximummolar absorptivity coefficient occurred at 287 nm (average 1.481 ± 0.008 × 10 4 L mol -1 cm -1 ), leadingto the determination of metal ion concentrations one hundred times lower than the ones formerlydetermined in the visible region. The system obeys Beer’s Law and is suitable for chromiumdetermination in the 0.702-2.81 mg L -1 concentration range (15-65% T, 1.00 cm-width quartz cells).Analytical applications of the current method were tested with a nutritional supplement containingchromium. Results were compared with those obtained with atomic absorption spectrometry.

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“…Studies on complexes formation, their respective stabilities (equilibria) and/or analytical utilization have been accomplished in a systematic way in some laboratories, especially when systems involving pseudohalide or halide ligands with transition metal cations [1][2][3][4][5][6][7][8][9][10][11][12][13] are concerned. The intense red colour characteristic of the compounds formed between iron(III) and thiocyanate ions in acidic aqueous medium is one of the strongest evidences of the chemical analogy existing between these species (SCN -) and azide (N 3 ) ligands.…”

Section: Introductionmentioning

confidence: 99%

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

Martins¹,

Andrade²,

Pimenta³

et al. 2005

Eclet. Quím.

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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).

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"Estudo espectrofotométrico do sistema crômio(III)/azoteto e seu aproveitamento analítico".

Abstract: Pimenta e Jorge Ricardo Moreira Castro pela constante ajuda nos momentos mais difíceis deste trabalho. Ao companheiro Santones do laboratório e Olímpia Rufino.

Cited by 4 publications

References 1 publication

Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

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

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