A new spectrophotometric method for the determination of ferrous iron in the presence of ferric iron

A new spectrophotometric method for the determination of ferrous iron concentration in samples containing ferric iron is presented. This new method is a modification of the Muir o-phenanthroline ferrous iron determination method. The new method consists of the quantitative spectrophotometric determination of Fe(II) by o-phenanthroline, but in which the ferric iron is complexed with sodium fluoride to eliminate interferences. A critical experimental comparison between the Muir spectrophotometric method, the Kolthoff titrametric method and the new proposed method is presented. Whenever Fe(III) accounts for more than 50% of the total iron in a sample, the method of Muir overestimates Fe(II). The proposed method has a range of 1–10 μg ferrous iron. It is as insensitive to other metal ions as the original method of Muir and is insensitive to Fe(III) up to a point where Fe(III) might be as high as 95% total iron. The proposed method is suitable for Fe(II) determination in bacterial leaching systems, where Fe(II) might be as low as 1% of total iron.     

Flow injection analysis of iron in rain water with thiocyanate and surfactant

This paper explains a new procedure for flow injection analysis (FIA) determination of iron in rain water based on the colour reaction of Fe³⁺ with thiocyanate ions in the presence of the cationic surfactant cetylpyridinium chloride (CPC). The value of apparent molar absorptivity of the complex in terms of iron is (2.00) x 10⁴ l mole^-1 cm^-1 at an absorption maximum of 490 nm. The detection limit of the method is 8 ppb Fe. The sample throughput is 90 samples/h at a flow rate of 4.0 ml/min. The reaction mechanism, optimization of FIA variables, and effect of various types of surfactant are described. None of the tested anions and cations interfered with the determination of iron. The method was used for the quantification and flux determination of iron in rain water.     

Oxidation of iron (II) sulphate to iron (III) sulphate and use in water treatment

Iron (II) sulphate, a side product of the steel industry, can react with nitric acid in the presence or absence of sulphuric acid to give a solution of iron (III) sulphate and nitrate. This solution seems to be a good substitute for iron (III) chlorosulphate as a coagulant in water treatment processes. In the present work, a kinetic study of the different reactions taking place has been realised. Experimental measurements of the conversion of Fe(II) to Fe(III) have been carried out by means of a volumetric method. The influence of various operating parameters such as the reaction temperature and the concentration of reagents has been studied. Global kinetic data such as the reaction orders, the reaction rates and the activation energy have been determined. Measurements of the water turbidity and the concentrations of undesirable products such as nitrates, have been taken prior to and after the treatment process and are also reported.     

Synthesis of a new iron (III) porphyrin acrylate-styrene copolymer and its catalysis for hydroxylation of cyclohexane

A new iron (III) porphyrin acrylate-styrene copolymer, P[(PorFe)A-S], was synthesized by the reaction of iron (III) porphyrin acrylate with styrene and characterized by UV-Vis, Infrared spectra (IR), inductively coupled plasma-atomic emission spectrometry (ICP) and molecular weight determination. Its catalytic activity in the hydroxylation of cyclohexane for model cytochrome P450 in the P[(PorFe)A-S]-O₂ ascrobate-thiosalicylic acid system has been studied. It was found that the P[(PorFe)A-S] has a higher catalytic activity than non-supported iron (III) porphyrin and its high catalytic activity remained in reuse. The catalytic activity of P[(PorFe)A-S] was discussed in the view of the microenvironment of iron (III) porphyrin. It is proposed that the atalytic activity of the P[(PorFe)A-S] may be further enhanced by construction of a homophase catalytic system containing the iron (III) porphyrin acrylate-styrene copolymer.     

Spectrophotometric study of the complexation equilibria of iron(III) with 3-hydroxypicolinic acid and determination of iron in pharmaceutical preparations

The complexation equilibria of iron(III) with 3-hydroxypicolinic acid (hypa) have been studied spectrophotometrically in 40% (v/v) ethanol—water medium at 25°C and an ionic strength of 0.1 M NaClO₄. The equilibria occurring in solution were established and the basic characteristics of the complexes formed were determined. The spectral study of the reaction solutions containing equimolar concentrations or an excess of one component in the pH range 1.5 to 10.5 gave the evidence for the formation of [FeLH]²⁺, [FeL]⁺ and [FeL₂]^? complex species, depending upon the pH of the medium (LH₂ symbolising the molecular form of hypa). The possible complex transitions that occur in solution were demonstrated using graphical and logarithmic analysis of the absorbance—pH graphs. A simple, rapid, sensitive and selective method for spectrophotometric determination of trace levels of iron(III) was proposed based on the formation of Fe(hypa)₂ complex at pH 5.5 (λ = 440 nm, ? = 1.5 × 10⁴ dm³ mol^?1 cm^?1). The interference of a large number of foreign ions was investigated. The method has been applied successfully to the analysis of multivitamin and mineral preparations containing iron.     

Synthesis of a new iron(III) porphyrin acrylate-styrene copolymer and its catalysis for hydroxylation of cyclohexane

A new iron(III) porphyrin acrylate-styrene copolymer, P[(PorFe)A-S], was synthesized by the reaction of iron(III) porphyrin acrylate with styrene and characterized by UV-Vis, Infrared spectra (IR), inductively coupled plasmaatomic emission spectrometry (ICP) and molecular weight determination. Its catalytic activity in the hydroxylation of cyclohexane for model cytochrome P450 in the P[(PorFe) A-S]-O₂-ascrobate-thiosalicylic acid system has been studied. It was found that the P[(PorFe)A-S] has a higher catalytic activity than non-supported iron(III) porphyrin and its high catalytic activity remained in reuse. The catalytic activity of P[(PorFe)A-S] was discussed in the view of the microenvironment of iron(III) porphyrin. It is proposed that the catalytic activity of the P[(PorFe)A-S] may be further enhanced by construction of a homophase catalytic system containing the iron(III) porphyrin acrylate-styrene copolymer. Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2006, 45(1): 61–63 [译自: 中山大学学报 (自然科学版)]     

硫铁矿废水制备铁黑颜料的工艺

采用湿法氧化沉淀法,通过调节反应溶液初始pH值(7～12)、反应温度(70～95℃)、反应时间(1～4.5h)和搅拌速度(50～250r/min),探索了硫铁矿废水制备铁黑颜料的工艺条件。结果表明:在pH值为9.5、反应温度为85℃、反应时间为2.5h、搅拌速度为150r/min的条件下,能制备得到较优的铁黑颜料。其经XRD、SEM及铁黑颜料技术指标检测分析,表明该铁黑颜料粒径在60nm左右,Fe3O4含量在95%以上,各项指标均能达到氧化铁黑颜料行业标准中一级品的要求。     

黄钠铁矾渣及其浸取液中铁的测定

黄钠铁矾渣中铜的含量较高,用重铬酸钾容量法来测定其中的铁时,干扰铁的测定,需预分离才能准确测量。但在用铁还原法浸取黄钠铁矾渣后的浸出液中,由于部分铜被除去,铜的含量降低,不干扰铁的测定,无须预分离,直接测定。试验结果表明,当铜的含量占铁量的4%时,干扰铁的测定。     

Copper and Iron Determination with [<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-Bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] in Edible Oils Without Digestion

A new method for the determination of copper(II) and iron(III) in liquid edible oils which does not require a digestion step was developed. The suggested method involves extraction of metals with [N,N′-bis(salicylidene)-2,2′-dimethyl-1,3-propanediaminato] (LDM) followed by flame atomic absorption spectrometry measurement. As a first step, metal complexes of copper(II) and iron(III) ions with LDM were investigated spectrophotometrically. After the analytical properties and experimental conditions of the complexation had been determined, these findings were used to determine the extraction period as a second step. Experimental conditions were optimized using a central composite design. Optimum conditions for Cu(II) and Fe(III) extractions from oil were found: the ratios of the volume of Schiff base solution used to the mass of oil (V _LDM/m _oil; mL g⁻¹) were 0.76 and 1.19 mL g⁻¹, the stirring times were 73 and 67 min, and the temperatures were 31 and 28 °C, respectively. The developed extraction and determination method was tested on certified reference materials; the recovery percentages were found to be 99.4 ± 2.8 and 100.2 ± 5.6 for Cu(II) and Fe(III), respectively. The suggested method was performed on real samples such as olive oil, sunflower oil, corn oil, canola oil and recovery values between 97.2–102.1 for Cu(II) and 94.5–98.6 for Fe(III) were determined. It was concluded that the developed method has some advantages over the common traditional method including rapidity, sensitivity, accuracy, reduced risk and cost.     

Fast photometric determination of iron impurity in red lead and litharge

A method for fast photometric determination of iron impurity in red lead and litharge is suggested. The method is based on the use of reactions of complexation of iron(II) and 2,2-dipyridyl or 1,10-phenanthroline after dissolution of a specimen in a mixture of acetic acid and hydrogen peroxide and reduction of iron(III) to iron(II) by ascorbic acid.Translated from Steklo i Keramika, No. 3, pp. 28–29, March, 1995.     

Iron(III) chelating resins. VI. Stability constants of iron(III)–ligand complexes on insoluble polymeric matrices

A method is presented for the determination of stability constants of iron(III)–ligand complexes on insoluble polymeric matrices based on a competition chelation reaction for iron(III) of the resin with a soluble chelator. Stability constants (K') were calculated for iron(III)–ligand complexes on DFO–Sepharose gel, HMP–Sepharose gel, AHMP–HEMA resin, and AHMP–DMAA resin. In these resins, desferrioxamine B (DFO, hexadentate ligand) or the 3-hydroxy-2methyl-4(1H)-pyridinone (HMP, bidentate ligand) was bound on insoluble polymeric matrices. The average values (log K') were: 26.6 (DFO–Sepharose); 37.9 (HMP–Sepharose); 27.2 (AHMP–HEMA); and 39.9 (AHMP–DMAA). The stability constants of the insoluble iron(III) complexes on the resins were compared with those of the corresponding soluble iron(III) complexes. The effect of immobilization on the constants was discussed, and it was found that a higher hydrophilicity and stability of a resin resulted in an increase of the stability constant, whereas steric hindrance decreased the stability constant. © 1995 John Wiley & Sons, Inc.     

Fast chromogenic identification of phenolic pollutants via homogeneous oxidation with t-BuOOH in the presence of iron (III) octacarboxyphthalocyanine

An efficient method has been developed for fast chromogenic identification of some phenolic pollutants (phenol, 2-chlorophenol and 1-naphthol) via tert-butyl hydroperoxide (t-BuOOH) oxidation in the presence of water-soluble iron (III) octacarboxyphthalocyanine complexes (catalyst) and 4-aminoantipyrine (chromogenic reagent). Among them, the chromogenic reaction of 2-chlorophenol could be completed rapidly, just within 6 min. The catalytic mechanism and detailed dye formation process were proposed on the basis of control experiments under different conditions. Potentially, the catalytic system composing of iron (III) octacarboxyphthalocyanine and t-BuOOH is promising for the application in fast chromogenic assay of phenolic pollutants.     

A rapid spectrophotometric method for the determination of peroxide value in food lipids with high carotenoid content

A rapid and sensitive ultraviolet-visible spectrophotometric method for determination of peroxide value (PV) in foods with high carotenoid content (e.g., paprika oleoresin, paprika powder, red palm oil) has been developed. The proposed protocol [modified International Dairy Federation (IDF) method] was established from the IDF Fe(II)-oxidation-based spectrophotometric method, and the main one of the introduced modifications consisted of a clean-up extraction step of pigments before determining the PV by complexing Fe(III) ions with thiocyanate. Fe(II) oxidation time, reaction medium, and Fe(III)-thiocyanate complex formation time were optimized. The modified IDF method was compared with and was validated by iodometric AOAC official method with a good correlation (R ²=0.957) between data obtained by both analytical methods. The high sensitivity of the method allows the use of only about 0.010–0.015 g of sample, with a detection limit of 0.044 mequiv peroxide/kg of sample. Therefore, an improved spectrophotometric method for assessing PV in food lipids with high carotenoid content is now available and can be applied to any kind of sample, independent of oil and pigment content.     

Polymerization of Aniline Using Iron(III) Catalyst and Ozone,and Kinetics of Oxidation Reactions in the Catalytic System

The environmentally benign polymerization of aniline provided polyaniline with an emeraldine structure by using iron(III) and ozone which is easily converted from oxygen in air. The influence of the reaction temperature upon the molecular weight of the polyaniline in this system is different from that in the polymerization of aniline using ammonium peroxodisulfate as an oxidant. Although the polyaniline prepared here has low molecular weight, the low molecular weight of the polyaniline does not significantly influence the electrical conductivity of cast films. In contrast, this can provide an advantage for the engineering of polyaniline through solution‐processing. Kinetics of oxidation reactions in the polymerization, systematically investigated here, has revealed that polyaniline is produced catalytically in terms of iron(III) and that an oxidation reaction of iron(II) to iron(III) could be a rate‐determining step in the polymerization.     

Homogeneous Catalytic Isomerization of Allylbenzene and Phenylbutenes by Some Platinum-Metal Oomplexes

The isomerization of Allylbenzene, p-allylanisole, 4-phenylbut-1-ene and trans-1-phenylbut-2-ene catalyzed by various ruthenium, rhodium and iridium complexes has been investigated. At the boiling point of the olefins the reaction does not require co-catalysts. The activity of the complexes studied decreases in the order Ru > Ir > Rh. PPh₃ and AsPh₃ increase the initial rates of the Rh (III), catalyzed reactions, decrease the activities of Rh (I)- and Ir (I)-complexes and do not affect the Ru (II)-compound. Different mechanisms for the rhodium- and ruthenium-catalyzed isomerizations are suggested.     

氧化铁对焦炭溶损反应的影响

在井式硅钼棒电炉中对焦炭溶损反应性进行研究,考察了反应条件(CO₂流量、反应时间)并重点研究负载氧化铁对焦炭溶损反应性的影响;通过扫描电子显微镜(SEM)和电子能谱(EDS)对反应前后负载氧化铁的焦炭进行分析,探究氧化铁负载方式对焦炭溶损反应影响差异的原因,并进一步分析比较其影响机理。结果表明:焦炭溶损反应性随CO₂流量和反应时间的增加而增大;以吸附法和添加法负载氧化铁对焦炭溶损反应均有促进作用,氧化铁吸附负载量存在一个饱和点(1%),超过该点后氧化铁吸附负载量对焦炭溶损反应性影响甚微;吸附法负载氧化铁对焦炭溶损反应性的影响大于添加法。SEM分析表明:添加法的部分铁氧化物被焦炭气孔壁基质包裹而无法发挥作用,吸附法的氧化铁均匀分布在焦炭表面使其能提供更多有效催化活性中心;且添加氧化铁时铁氧化物参与成焦,影响焦炭结构从而对焦炭溶损反应产生影响,吸附氧化铁则是影响焦炭溶损反应的催化作用,两种负载方式下氧化铁的影响机理不同。     

保险粉中铁含量的测定

介绍了用盐酸溶解保险粉样品,分光光度法测定保险粉中铁含量的方法。用盐酸溶解保险粉样,剩余溶液蒸发干涸至硫燃尽,避免了保险粉中杂质对铁含量测定的干扰,解决了采用常规化工产品中铁含量测定方法来测定保险粉中铁结果偏低的问题。该方法具有精密度好,准确度高等优点,用于保险粉中铁含量的测定,结果令人满意。     

Adsorption of N-phenylmaleimide and its derivatives on iron electrodes in sulfuric acid solutions

The adsorption of N-(phenyl)maleimide and its derivatives on iron electrodes in sulfuric acid medium has been studied by the capacitance method. The process investigated is well described by Frumkin's isotherm. The adsorption parameters characterizing the interaction forces between the species in the adsorbed layer, the area occupied by each species and the maximum surface excess have been calculated on the basis of this isotherm. Combining data from the electrochemical method with quantum-chemical calculations of the chemical structure and the partial electronic charges of the compounds studied a mechanism of adsorption on the iron surface is proposed. The inhibiting effect observed is explained in relation to the adsorption behaviour.     

Reversible photochemically-genated pH changes in the thionine—iron system

The pH change generated by irradiating thionine—iron(II) solutions with visible light to the photostationary state has been measured in the pH range 1–2 and at two thionine concentrations. The small pH increases found are consistent with the assumed photoredox proton uptake stoichiometry with allowance for iron(III) hydrolysis.     

Elucidation of the iron chloride-clay system for removal of nitrogen-containing compounds from petroleum and shale-oil distillates

Hydrated iron (III) chloride adsorbed on attapulgus clay has been reported as a method for removing nitrogen-containing compounds from petroleum and shale-oil distillates. The preparation of an improved nitrogen removal system using the anhydrous iron salt is reported here. Reaction of the system with amines gives products which appear to contain the normal iron(III) chloride complexes. It is proposed that the iron(III) chloride is acting as a Lewis acid in the removal process.