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

Chacarolli, C.J; Andrade, José Fernando de; Guimarães, Orliney Maciel; Balbo, Valdir Roberto; Venezuela, C.S; Teruel, F.S

doi:10.1016/s0003-2670(00)00778-9

Cited by 14 publications

(10 citation statements)

References 11 publications

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“…Similarly, when 100 μM sodium azide was mixed with 1.0 mM ferrous ions at pH 1.7, a new absorbance band with a peak at 380 nm formed rapidly and spontaneously in the spectrophotometer (data not shown). This spectrum was identical to that published previously for a aqueous complex of Fe(II) with azide (Chacarolli et al, 2000 ). Interestingly, when 100 μM sodium azide was mixed with intact bacteria in the absence of Fe(II) at pH 1.7, the cytochrome 579 was reduced to the same extent as that shown in Figure 3 or Figure 4 (data not shown).…”

Section: Discussionsupporting

confidence: 89%

In situ spectroscopy on intact Leptospirillum ferrooxidans reveals that reduced cytochrome 579 is an obligatory intermediate in the aerobic iron respiratory chain

Blake

Griff

2012

Front. Microbio.

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Electron transfer reactions among colored cytochromes in intact bacterial cells were monitored using an integrating cavity absorption meter that permitted the acquisition of accurate absorbance data in suspensions of cells that scatter light. The aerobic iron respiratory chain of Leptospirillum ferrooxidans was dominated by the redox status of an abundant cellular cytochrome that had an absorbance peak at 579 nm in the reduced state. Intracellular cytochrome 579 was reduced within the time that it took to mix a suspension of the bacteria with soluble ferrous iron at pH 1.7. Steady state turnover experiments were conducted where the initial concentrations of ferrous iron were less than or equal to that of the oxygen concentration. Under these conditions, the initial absorbance spectrum of the bacterium observed under air-oxidized conditions was always regenerated from that of the bacterium observed in the presence of Fe(II). The kinetics of aerobic respiration on soluble iron by intact L. ferrooxidans conformed to the Michaelis–Menten formalism, where the reduced intracellular cytochrome 579 represented the Michaelis complex whose subsequent oxidation appeared to be the rate-limiting step in the overall aerobic respiratory process. The velocity of formation of ferric iron at any time point was directly proportional to the concentration of the reduced cytochrome 579. Further, the integral over time of the concentration of the reduced cytochrome was directly proportional to the total concentration of ferrous iron in each reaction mixture. These kinetic data obtained using whole cells were consistent with the hypothesis that reduced cytochrome 579 is an obligatory steady state intermediate in the iron respiratory chain of this bacterium. The capability of conducting visible spectroscopy in suspensions of intact cells comprises a powerful post-reductionist means to study cellular respiration in situ under physiological conditions for the organism.

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Section: Discussionsupporting

confidence: 89%

In situ spectroscopy on intact Leptospirillum ferrooxidans reveals that reduced cytochrome 579 is an obligatory intermediate in the aerobic iron respiratory chain

Blake

Griff

2012

Front. Microbio.

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“…4, at a ligand concentration close to that considered ideal in aqueous medium (500 mmol L -1 ), the presence of ethanol only brought about a small increase to absorbance values, making the aqueous medium the most promising for the accomplishment of the measurements. The use of solvents such as acetone and tetrahydrofuran did not provide the solvatochromic effects for the present chromium(III)/azide system, as observed previously [9][10][11][12].…”

Section: Resultssupporting

confidence: 48%

“…Azide 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).…”

Section: Introductionmentioning

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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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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“…A spectrophotometric method described for the determination of iron (II) by its oxidation to iron (III) by tetrahydrofuran/water and then reacted with azide reagent to form coloured complex at 396 nm (5) . Iron (II) has been determined by sequential injection analysis method.…”

Section: Introductionmentioning

confidence: 99%

Spectrophotometric Assay of Iron (II) in Pharmaceutical Formulation Using Alizarin Red Sulphonate Reagent

Al-Neaimy¹,

Saeed²,

Al-Ghabsha³

2012

J.Edu.Sci.

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

Cited by 14 publications

References 11 publications

In situ spectroscopy on intact Leptospirillum ferrooxidans reveals that reduced cytochrome 579 is an obligatory intermediate in the aerobic iron respiratory chain

In situ spectroscopy on intact Leptospirillum ferrooxidans reveals that reduced cytochrome 579 is an obligatory intermediate in the aerobic iron respiratory chain

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

Spectrophotometric Assay of Iron (II) in Pharmaceutical Formulation Using Alizarin Red Sulphonate Reagent

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