Simultaneous determination of trace iron and aluminum by catalytic spectrophotometry based on a novel oxidation reaction of xylene cyanol FF.

A new, simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry was presented, based on the catalytic effects of iron and aluminum on the discoloring reaction of xylene cyanol FF proceeded by hydrogen peroxide and potassium periodate in weak nitric acid medium. No catalytic effect was obtained in the presence of hydrogen peroxide or potassium periodate only. With the conditional rate constants determined in reaction systems catalyzed by Al or Fe only, the concentrations of Fe and Al in the samples can be calculated. The method was applied to the simultaneous determination of trace Fe and Al in tap water, lake water, river water and tea leaves without separation and preconcentration.     

A New Catalytic Reaction for the Determination of Nanomolar Concentrations of Iron(III)

Abstract

On the basis of theoretical considerations, a new catalytic reaction for the determination of nanomoler iron(III) concentrations has boon propesod, nomoly the oxidation of sulfanilic acid by potassium periodate using 1,10-phenanthroline as an activator. The optimum conditions for Fe(III) determination have been established as a result of kinetic studies.

The reaction ensures a low detection limit (2×10^?8 M), low coefficient of variation about 5% and high selectivity.     

Catalytic kinetic simultaneous determination of iron, silver and manganese with the Kalman filter by using flow injection analysis stopped-flow spectrophotometry

A catalytic differential kinetic method with Kalman filter for the simultaneous determination of multi-component is described. The oxidization of Rhodamine B (RB) by potassium periodate in a slightly acid solution is a slow reaction. But iron(III), silver(I) or manganese(II) has a differential catalytic effect on the oxidation reaction of RB in the presence of 1,10-phenanthroline as the activator. So iron, silver and manganese can be simultaneously determined by measuring the decreasing absorbance of the dye (RB) at 555 nm. A flow injection analysis stopped-flow spectrophotometric system with a microcomputer performs the determinations. This method has been applied to determining iron, silver and manganese of alloy samples with satisfactory results.     

Spectrophotometric determination of iron with ferrozine by flow-injection analysis

Two methods for the determination of iron by normal FIA and reversed FIA were developed using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine). The reagent formed a chelate with Fe(II) in hexamethylentetramine buffered medium at pH 5.5. In one previous reaction coil Fe(III) was reduced to Fe(II) by ascorbic acid and in the other reaction coil the complexation reaction was developed. The linear range of the determination was 0.5-6 and 0.1-5 mug ml(-1) of iron for normal FIA and reversed FIA respectively. The proposed method was sensitive (detection limit 0.012 and 0.010 mug ml(-1)), rapid and reproducible (RSD 0.3 and 0.28%). The method was satisfactorily applied to the determination of iron in waste water, toadstool tissue, potato leaves, human hair and bauxites at a sampling rate of 90 and 50 samples h(-1) for normal FIA and reversed FIA respectively.     

A new catalytic kinetic spectrophotometric method for determination of iron

The catalytic effect of iron(III) on the oxidation of reduced Rhodamine B with hydrogen peroxide in acetic acid medium has been studied. The reaction is highly accelerated by potassium thiocyanate. A new catalytic kinetic spectrophotometric method for the determination of iron has been developed. Iron(III) can be determined by the fixed time method with a detection limit of 4 x 10(-11) g/ml.     

Indirect spectrophotometric determination of ascorbic acid with ferrozine by flow-injection analysis

A FIA indirect spectrophotometric determination of ascorbic acid was developed using its reducing action on Fe(III) in acidic medium and following the spectrophotometric determination of the reduced iron by using sodium 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4',4'-disulphonate (ferrozine) as chromogenic reagent in buffered medium (pH 5.5) and monitoring the absorbance signal at 562 nm. A three-line manifold with two reaction coils was used: in the first reaction coil, ascorbic acid reduces Fe(III) to Fe(II); and in the second one, the complexation reaction is developed. The linear range of the method was 0.5-10 mug ml(-1) of ascorbic acid, the detection limit being 0.028 mug ml(-1). The proposed method was sensitive, rapid (sampling rate of 90 samples h(-1)) and reproducible (RSD 0.19%, n=10). Satisfactory results were obtained in the determination of ascorbic acid in pharmaceutical preparations, fruit juices and urine testifying the applicability of the method to real samples.     

Catalytic determination of ultratrace amounts of ruthenium with oscillopolarographic detection

The oscillopolarographic behaviour of Methyl Red in sodium hydroxide medium has been studied, and the results show that the wave at -0.79 V is an irreversible two-electron adsorption wave. A very sensitive and selective catalytic reaction-oscillopolarographic method for the determination of Ru down to 3 ng/l. is described, based on the Ru(III)-catalysed redox reaction of Methyl Red and potassium periodate in hydrochloric acid medium. Potassium thiocyanate is used to quench the reaction and the oscillopolarography is then performed with sodium hydroxide as the supporting electrolyte. The influence of 41 foreign ions has been examined. Ruthenium in ore samples has been determined by the method, with satisfactory results.     

Catalytic spectrophotometric determination of trace aluminium with indigo carmine

A new catalytic spectrophotometric method is described for the determination of trace amounts of Al(III). The methods based on catalytic action of Al(III) on the oxidation of indigo carmine (IC) by ammonium persulfate in hexamethylene tetramine-hydrochloric acid ((CH2)6N4-HCl) buffer medium (pH 5.4) and in the presence of surfactant-TritonX-100. The effects of some factors on the reaction speed were investigated. Aluminium concentration is linear for 0-1.2x10(-7) g/ml in this method. The detection limit of the proposed method is 1.96x10(-8) g/ml. Most of the foreign ions except for Cu(II), Fe(III) do not interfere with the determination, and the interference of Cu(II) and Fe(III) in this method can be removed by extraction with sodium diethyldithiocarbamate-carbon tetrachloride (DDTC-CCl4). This system is a quasi-zero-order reaction for Al(III), but it is a quasi-first-order reaction for IC. The apparent rate constant is 2.62x10(-5) s-1 and the apparent activation energy is 6.60 kJ/mol in the system. The proposed method was applied to the determination of trace aluminium(III) in real samples with satisfactory results.     

Catalytic Spectrophotometric Determination of Rhodium in The Rhodium-Potassium Periodate-Ethylrhodamine B

The method of kinetic spectrophotometry for determination of trace Rh(Ⅲ) had been reported by reference. We have discovered that trace the Rh(Ⅲ) catalyze the decolorating oxidizine reaction of ethylrhodamine B by potassium periodate on heating in phosphoric acid and sodium chloride medium, the reaction rate on log(A₀/A) values is linear over relatively range of concentration of Rh(Ⅲ). Hence a new catalytic spectrophotometric method for determination of trace Rh(Ⅲ) has been established. The method is simple,rapid and reproducible. The method has been used to determine trace Rh(Ⅲ) in actual samples with satisfactory results.     

Determination of total and dissolved amount of iron in water samples using catalytic spectrophotometric flow injection analysis

A flow injection spectrophotometric method has been developed for the determination of dissolved and total amounts of iron in tap and natural water samples. The method for the determination of iron employs a sample acidification step in order to decompose iron hydroxide and iron-complexes into free iron, Fe(III) and Fe(II). The amounts of free iron were detected using a catalytic action of Fe(III) and Fe(II) on the oxidation of N,N-dimethyl-p-phenylenediamine in the presence of hydrogen peroxide. Increase in absorbance of oxidized product was detected spectrophotometrically at 514 nm. The proposed method allows 0.02 and 0.06 μg l⁻¹ of LOD and LOQ, respectively, with relative standard deviation (RSD) below 2%. The accuracy and the precision of the method were evaluated by the analysis of the standard reference material, river water. The developed method was successfully applied to real water samples.     

Flow-injection manifold for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) using 2,2''-dipyridyl-2-pyridylhydrazone and a single-line double injection approach

A simple and rapid flow-injection (FI) method is reported for the simultaneous spectrophotometric determination of Fe(II) and Fe(III) in pharmaceutical products. The method is based on the reaction of Fe(II) with 2,2'-dipyridyl-2-pyridylhydrazone (DPPH) in acidic medium to form a water-soluble reddish complex (lambdamax=535 nm). Fe(III) reacts with DPPH under flow conditions only after its on-line reduction by ascorbic acid (AsA). Both analytes were determined in the same run via a double-injection valve, which enabled the simultaneous injection of two sample volumes in the same carrier stream (,,single-line double-injection" approach). The two well-defined peaks produced corresponded to total iron [Fe(II)+Fe(III)] and Fe(II). Speciation of the analytes in their mixtures was achieved by multiple regression analysis. The calibration curves obtained were linear over the ranges 0-30 and 0-50 mg L(-1) for Fe(II) and Fe(II), respectively, and the precision [s(r)=1.0% for Fe(II) and 1.5% for Fe(III)] was satisfactory. The method proved to be selective and adequately sensitive (cL=0.25 and 0.17 mg L(-1) for Fe(III) and Fe(II), respectively, in mixtures). Application of the method to the analysis of pharmaceutical samples resulted in excellent accuracy; the percent mean recoveries were in the range 99.0-102.0% for both Fe(II) and Fe(III) and the mean relative error was e(r)=1.0%.     

Kinetic spectrophotometric determination of Fe(II) in the presence of Fe(III) by H-point standard addition method in mixed micellar medium

The H-point standard addition method was applied to kinetic data for simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III). The method is based on the difference in the rate of complex formation between iron in two different oxidation states and methylthymol blue (MTB) at pH 3.5 in mixed cetyltrimethylammonium bromide (CTAB) and Triton X-100 micellar medium. Fe(II) can be determined in the range 0.25-2.5 microg ml(-1) with satisfactory accuracy and precision in the presence of excess Fe(III) and other metal ions that rapidly form complexes with MTB under working condition. The proposed method was successfully applied to the simultaneous determination of Fe(II) and Fe(III) or selective determination of Fe(II) in the presence of Fe(III) in spiked real environmental and synthetic samples with complex composition.     

Flow injection determination of iron by its catalytic effect on the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide

A flow injection-photometric method has been developed for the determination of iron(II+III). The method is based on the catalytic effect of iron(III) on the hydrogen peroxide oxidation of 3,3',5,5'-tetramethylbenzidine to form a blue compound (lambda(max)=650 nm). In this catalyzed reaction, 1,10-phenanthroline acted as an effective activator. Iron(II) is also determined, being oxidized by hydrogen peroxide. Calibration graphs for iron(II) and iron(III) obtained under the optimized conditions were identical with each other and linear in the range 0.2-200 ng ml(-1) with a detection limit of 0.05 ng ml(-1) iron. The reproducibility was satisfactory with a relative S.D. of 1.0% for ten determinations of 5 ng ml(-1) iron(III). The proposed method was successfully applied to the determination of iron in river and lake water samples and can be determined free iron species.     

Selective determination of trace iron in different oxidation states in natural water by flow injection-solid phase spectrometry

A novel method for the selective determination of Fe(II) and Fe(III) in water using 2-nitroso-5-[N-n-propyl-N-(3-sulfopropyl)amino]phenol (PSAP) was developed. QAE-Sephadex anion exchanger packed in a flow-through cell was used as a medium not only for both the concentration and the spectrophotometric measurements of the Fe-PSAP complex, but also for reduction of the Fe(III)-PSAP complex. The PSAP complex of Fe(II) or Fe(III) was strongly adsorbed on the anion exchanger in a weakly acidic to weakly basic region, but the Fe(III) complex was readily and completely reduced to the Fe(II) complex only in a neutral to weakly alkaline region in the solid phase. These properties were utilized to determine the Fe(II) and total Fe concentration without the addition of any reducing agent. The detection limits (3σ) were 0.18 ng for Fe(II) and 0.18 ng for total Fe using a 3.2-cm(3) sample solution. The present method is applicable to the determination of dissolved iron species present at μg dm(-3) levels in natural water samples.     

Microanalytical method development for Fe, Cu and Zn determination in colorectal cancer cells

Microanalytical methods suitable for the determination of Fe, Cu in HT-29 (human colon adenocarcinoma) cells treated with different iron compounds (Fe(II) sulfate, Fe(III) chloride, Fe(III) citrate and Fe(III) transferrin) and cultured in medium supplemented or not with 10% (v/v) fetal calf serum (FCS) by total reflection X-ray fluorescence spectrometry (TXRF) and simultaneous graphite furnace atomic absorption spectrometry (GF-AAS) were developed. The developed TXRF method was also suitable for Zn determination in the samples. The main advantage of the proposed methods is the execution of all sample preparation steps following incubation and prior to the elemental analysis in the same Eppendorf tubes. Sample preparation was performed at microscale (115 μL sample volume) with 65% nitric acid and 30% hydrogen peroxide. According to scanning electron microscopic measurements, the organic matrix of the cell samples could be eliminated to the extent that accurate results were obtained for Cu and Fe by analyzing the same samples by TXRF and GF-AAS. Concerning the iron uptake, HT-29 cells incubated in FCS-free medium contained Fe in cca. 5-50 times higher amounts compared to cells cultured in FCS supplemented medium. Pronounced differences in the iron uptake compared to the iron supply (inorganic vs. organic chelated as well as iron(II) vs. iron(III)) were observed in the case of cell lines incubated in FCS-free medium.     

Simultaneous kinetic determination of Fe(II) and Fe(III) based on their reactions with NQT4S in micellar media by using PLS and PCR methods

Simultaneous determination of Fe(II) and Fe(III) was studied using partial least squares regression (PLS) and principal component regression (PCR) methods. The models were based on the difference observed in the rates of the complex formation of iron in its two oxidation states with 1,2-naphthaquinone-2-thiosemicarbazone-4-sulphonic acid (NQT4S) at pH 4.0 in cetyltrimethylammoniumbromide (CTAB) as micellar media. The results showed that simultaneous determination of Fe(II) and Fe(III) could be performed in their concentration ranges of 0.10-2.10 and 0.25-2.25 μg/ml, respectively. The models used can proceed the data with low percent relative error of prediction (i.e. <5.5%). The procedure was successfully applied for the simultaneous determination of Fe(II) and Fe(III) in some environmental samples. The method would allow the transformation of the two oxidation states of iron to be monitored overtime in a water sample.     

Kinetic spectrophotometric determination of trace manganese (II) with dahlia violet in nonionic microemulsion medium

A new catalytic kinetic spectrophotometric method has been developed for the determination of trace amount of manganese (II) in nonionic microemulsion medium. The method is based on the catalytic effect of manganese (II) on the oxidation of dahlia violet by potassium periodate with nitrilotriacetic acid as an activitor in the presence of nonionic microemulsion. Under the optimum conditions, the calibration graph is linear in the range of 0.0004-0.0056 μg ml⁻¹ of manganese (II) at 580 nm. The detection limit achieved is 3.75×10⁻⁵ μg ml⁻¹. Manganese (II) in foodstuff samples was determined with satisfactory results.     

Speciation of dissolved iron(II) and iron(III) in environmental water samples by gallic acid-modified nanometer-sized alumina micro-column separation and ICP-MS determination

A method has been developed for the speciation of trace dissolved Fe(II) and Fe(III) in water by coupling gallic acid (GA) modified nanometer-sized alumina micro-column separation with inductively coupled plasma mass spectrometry (ICP-MS). The separation of Fe(II) and Fe(III) was achieved based on the obvious difference in reaction kinetics between Fe(II) and Fe(III) with GA. Fe(III) was selectively retained on the micro-column at pH 5.5-6.5, while Fe(II) could not be retained by the micro-column at the whole tested pH range of 1.0-6.5, and passed through the micro-column. The Fe(II) can be determined by ICP-MS directly without preconcentration/separation procedure, while Fe(III) retained on the micro-column was then eluted with 1.0 mL of 1 mol L(-1) HCl and determined by ICP-MS. The parameters affecting the separation of Fe(II) and Fe(III) were investigated systematically and the optimum separation conditions were established. Under the optimized conditions, the detection limits of 0.48 microg L(-1) and 0.24 microg L(-1) with relative standard deviation of 5.6% and 4.3%(C= 5 microg L(-1), n= 7) for Fe(II) and Fe(III) were found, respectively. No obvious effect on the speciation of Fe(II) and Fe(III) was found with the change of the ratio of Fe(II) and Fe(III) from 0 ratio 10 to 10 ratio 0. The proposed method was applied for the determination of trace Fe(II) and Fe(III) in environmental water and the recoveries for spiked samples were found to be in the range of 97-105%.     

亚甲基蓝-高碘酸钾催化动力学光度法测定痕量钌(Ⅲ)

在稀H_2SO_4介质中及加热85℃的条件下,钌(Ⅲ)对KIO_4氧化亚甲基蓝的褪色反应具有显著的催化作用,建立了一个催化动力学光度法测定痕量钌(Ⅲ)的新分析方法.探讨了该催化反应的最佳实验条件.非催化反应吸光度A_0与催化反应吸光度A之间的差值△A与钌(Ⅲ)质量浓度ρ在0～0.06μg/mL范围内呈良好的线性关系,检出限为2.37×10~(-10)g/mL.测定了动力学参数,反应为准一级反应,表观速率常数为3.63×10~(-4)/s,表观活化能为58.13 kJ/mol.对1.0μg Ru(Ⅲ)测定的相对标准偏差RSD为1.7%(n=11).方法用于分子筛样品中痕量钌(Ⅲ)的测定,回收率98.3%.     

Catalytic activity of iron hydroxides and manganese hydroxides in the deoxygenation of water

Catalysts prepared by the modification of FIBAN K-4 and FIBAN X-1 fibrous ion exchangers with the hydroxides of iron and manganese were developed and tested in a water deoxygenation process. It was established that the samples obtained by the supporting of Fe(III) hydroxide onto the FIBAN X-1 ampholyte were most effective. The conclusion that the high activity of the catalytic system is caused by the formation of a mixed phase of Fe(II) and Fe(III) hydroxides of the spinel type containing mobile (weakly bound) lattice oxygen was made. A reaction scheme was proposed to explain the reaction mechanism.