Preparative gas chromatography of volatile metal compounds-I Separation of aluminium, chromium and iron beta-diketonates

The analytical gas chromatography of a range of fluorinated and unfluorinated beta-diketonates of aluminium, chromium and iron has been studied m detail and conditions have been established for their complete separation; the complexes of trifluoroacetylpivaloylmethane show the best characteristics for this purpose. A range of liquid phases and column conditions have been considered and Apiezon substrates have been shown to give optimal resolution. The technique has been extended to a preparative scale with up to 0.1-g chelate samples, and the efficiency of the process demonstrated by the removal of 2% proportions of two metal complexes from a sample of the third. Implications of the technique for the purification of metals are discussed.     

The separation of geometrical isomers and mixed ligand forms of cobalt(III) and chromium(III) β-diketonates by high-pressure liquid chromatography

Pairs of geometrical isomers of octahedral cobalt(III) and chromium(III) chelates of trifluoroacetylacetone, benzoylacetylacetone and 2,2-dimethylhexane-3,5-dione can be separated by adsorption h.p.l.c. on silica. Trends in elution and required solvent systems are noted and chelate elution is substantiated by mass spectral analysis of collected peaks. Mixed ligand chromium β-diketonates of trifluoroacetylacetone and hexafluoroacetylacetone are resolved in both isocratic and gradient elution modes. Detection with a chromium-specific d.c. argon plasma is reported; mass spectrometry is applied to elucidate elution patterns.     

Application of adsorptive stripping voltammetry to the speciation and determination of iron(III) and total iron in wines

An analytical procedure for the determination of iron(III) and total iron in wines based on adsorptive stripping voltammetry is described. Iron(III) was determined by using Solochrome Violet Red as chelating agent while catechol was used for the determination of the total iron content. Each chelate was adsorbed on the hanging mercury electrode and the reduction current of the accumulated chelate was measured. The results obtained from the application of this procedure to wine samples are discussed.     

Spectrophotometric studies on ion-pair extraction equilibria of the iron(ii) and iron(III) complexes with 4-(2-pyridylazo)resorcinol

The ion-pair extraction equilibria of the iron(II) and iron(III) chelates of 4-(2-pyridylazo)resorcinol (PAR, H(2)L) are described. The anionic chelates were extracted into chloroform with benzyldimethyltetradecylammonium chloride (QC1) as counter-ion. The extraction constants were estimated to be K(ex1)(Fe(II)) = [Q{Fe(II)(HL)L}](0)/[Q(+)][{Fe(II)(HL)L}(-)] = 10(8.59 +/- 0.11), K(ex2)(Fe(II)) = [Q(2){Fe(II)L(2)}](o)/ [Q(+)](2)[{Fe(II)L(2)}(2-)] = 10(12.17 +/- 0.10) and K(ex1)(Fe(III)) = [Q{Fe((III))L(2)}](o)/(Q(+)][{Fe(III)L(2)}(-)] = 10(6.78 +/- 0.15) at I = 0.10 and 20 degrees , where [ ](o) is concentration in the chloroform phase. Aggregation of Q{Fe(III)L(2)} in chloroform was observed and the dimerization constant (K(d) = [Q(2){Fe(III)L(2)}(2)](o)/[Q{Fe(III)L(2)}](o)(2)) was evaluated as log K(d) = 4.3 +/- 0.3 at 20 degrees . The neutral chelates of {Fe(II)(HL)(2)} and {Fe(III)(HL)L}, and the ion-pair of the cationic chelate, {Fe(III)(HL)(2)}ClO(4), were also extracted into chloroform or nitrobenzene. The relationship between the forms and extraction properties of the iron(II) and iron(III) PAR chelates are discussed in connection with those of the nickel(II) and cobalt(III) complexes. Correlation between the extraction equilibrium data and the elution behaviour of some PAR chelates in ion-pair reversed-phase partition chromatography is also discussed.     

过渡金属乙酰丙酮螯合物的体积排除色谱研究

用体积排除色谱方法研究了过渡金属Fe(Ⅲ)、Co(Ⅲ)、Cu(Ⅱ)、Ni(Ⅱ)的乙酰丙酮螯合物在四氢呋喃溶液中的加合和缔合行为。在溶液中乙酰丙酮钴(Ⅲ)以单个螯合物分子的形式存在,乙酰丙酮铜(Ⅱ)和乙酰丙酮铁(Ⅲ)与溶剂加合生成加合物,乙酰丙酮铁(Ⅲ)除加合物外还存在缔合度为2-10的多分散缔合物,乙酰丙酮镍(Ⅱ)水合物在四氢呋喃中产生了加合交换作用,同时存在缔合度为6左右的缔合物。色谱数据给出了螯合物、加合物及缔合物的相对含量。螯合物与相同分子量的聚苯乙烯相比,其保留体积的滞后以Ni相似文献   

Gas and liquid chromatographic determination of some metals as their di-isobutyldithiocarbamate chelates

Summary Gas and Liquid Chromatographic Determination of Some Metals as Their Di-isobutyldithiocarbamate Chelates Both reversed-phase liquid chromatography and gas chromatography permit the elution of the di-isobutyldithiocarbamate chelates of nickel(II), copper(II) and cobalt(III) at picogram level. The palladium(II) chelate can be used as internal standard. Gas chromatography can easily be applied to determination of these metals in aqueous samples. In the liquid chromatography, contact between any free ligand remaining after extraction and metal traces in the column packing materials or metal components of the system must be minimized before the determinations commence. The results indicate a need for further study of interferences. Di-isobutyldithiocarbamate appears to be a suitable chelating agent for use in both Chromatographic methods.     

Separation of divalent transition metal beta-diketonates and their adducts by supercritical fluid chromatography

A method for separation and detection of divalent transition metal beta-diketonates by adduct formation/supercritical fluid chromatography (SFC) with an open-tubular capillary column and a FID detector is described. The crystal structures of copper (Cu)-hexafluoro-acetylacetone (HFA) and Cu bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (THD) complexes have been determined by X-ray crystallography. The SFC behavior of Cu beta-diketonates shows a strong correlation with the structure of the complexes. The hydrated cu beta-diketonate complexes usually exhibit strong intermolecular interactions or decomposition in SFC. Formation of adducts with a neutral donor, such as tributyl phosphine oxide (TBPO), can greatly improve the SFC behavior and detection sensitivity of Cu(II) and Mn(II) beta-diketonates. The stoichiometry and thermal stability of the adducts Cu(II) and Mn(II) beta-diketonates with TBPO in supercritical CO(2) have also been investigated. The implications of utilizing adduct formation for supercritical fluid extraction (SFE) of divalent transition metals and for on-line coupled SFE/SFC analysis of divalent transition metals are discussed.     

Speciation of Fe(III) and Fe(II) in water samples by liquid–liquid extraction combined with low-temperature electrothermal vaporization (ETV) ICP-AES

The use of 1-phenyl-3-methyl-4-benzoylpyrazolone (PMBP) as extractant for separation of Fe(III) and Fe(II) and low-temperature vaporization of the Fe(III)–PMBP chelate into ICP-AES for their speciation analysis was investigated. The factors affecting the formation of Fe(PMBP)₃ chelate and its vaporization behavior were investigated in detail. PMBP was used not only as the extractant for the separation of Fe(III) and Fe(II) but also as the chemical modifier for the low-temperature ETV-ICP-AES determination of iron. Under the optimized conditions, the detection limit for iron(III) and iron(II) are both 3.2?ng/mL, with relative standard deviations of 3.9 and 4.5%, respectively. The proposed method was applied to the determination of trace iron in biological standard reference materials and the species in East Lake water samples, and the results obtained were satisfactory.     

Chelate adsorption for trace voltammetric measurements of iron(III)

Summary A very sensitive electrochemical stripping procedure for trace measurements of iron(III) is described. The chelate of iron with Solochrome Violet RS is adsorbed on the hanging mercury drop electrode, and the reduction current of the accumulated chelate is measured by voltammetry. The adsorption and redox behaviours are explored by cyclic voltammetry. The height of the chelate peak, which is about 0.28 V more negative than the peak of the free dye, is shown to be proportional to the iron concentration. Optimal experimental conditions include a preconcentration potential of –0.40 V, solution pH of 5.1 and a linear scan mode. The sharp chelate peak, associated with the effective interfacial accumulation, coupled with the flat baseline, facilitates measurements at the nanomolar and submicromolar concentration levels using short preconcentration times. The limit of detection after 1 min preconcentration is 0.04 gl^–1 (7 × 10^–10 M), and the relative standard deviation at the 10^–7 M level is 4.7%. The effects of possible interferences, due to coexisting metal ions or organic surfactants, are evaluated. The ability of measuring iron(III) in the presence of iron(II) is illustrated. Actual analyses of sea and tap waters are reported.

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Chelat-Adsorption für voltammetrische Spurenanalyse von Eisen(III)

     

Study of nitrophenols preconcentration using quinolin-8-ol immobilized on controlled-pore glass in the presence of iron(III). Chromatographic determination of dinoseb in lemon juice.

The efficiency of an adsorbent consisting of quinolin-8-ol immobilized on controlled-pore glass which was packed in a minicolumn to preconcentrate nitrophenols in the presence of iron(III) has been established. Retention was carried out at acidic pH in the presence of 20 mM iron(III). Methanol-30 mM formic acid-sodium formate aqueous solution (pH 4.2) (65:35) was used in a one-step elution. Determinations were carried out by using liquid chromatography with detection at 350 nm. Determination of trace amounts of dinoseb in lemon juice was carried out with a minimum sample preparation. Recoveries were between 89 and 100% at 200-33 micrograms l-1. The maximum admissible concentration in fruit juice dictated by the Spanish and European Community legislation can be measured.     

Mechanism of binding of iron to potential therapeutic chelating agents

To aid in designing new therapeutic iron chelating agents, the mechanism of iron binding to prototypic heterocyclic carboxaldehyde thiosemicarbazones has been studied. Based on molecular orbital and spectroscopic studies, iron (II) is found to bind in a covalent manner, while iron(III) seems to interact ionically. However, with both iron(II) and iron(III), chelate formation is dependent on charge interaction between the metal and the coordinating atoms of the ligand.     

Application of zone-melting technique to metal chelate systems-XI Refining of tetrakis(di-n-propionylmethanato)zirconium(IV) from hafnium and trace amounts of some other metals

The zone-melting method was applied to purification of tetrakis(di-n-propionylmethanato)zirconium(IV) which contained copper(II), nickel(II), cobalt(II and III), iron(III) and hafnium(IV) in the forms of their chelates with the common ligand. All minor components having effective distribution coefficients < 1 in the zirconium(IV) chelate were concentrated toward the terminal end of the refining column. When an aqueous solution of zirconium(IV) containing zinC(II) and manganese(II) in addition to the metal contaminants above was treated with di-n-propionylmethane to precipitate the chelate complexes, only zinc, iron and hafnium were found in the precipitated zirconium chelate. The first two were ettectively removed by zone-melting. Though the separation of hafnium was poorer, the technique was efficient enough for practical purposes.     

Über Ternäre Chelate des Eisen(III)-Ions mit Nitrilotriessigsäure und Phenolderivaten

On Ternary Chelates of the Iron(III) Ion formed with Nitrilo-Triacetic Acid and Derivatives of Phenol Ternary chelates of iron(III) ions are produced with nitrilo-triacetic acid and some derivatives of phenol in aqueous solution. Their reactions of formation have been controlled by spectro-photometric methods. The ratio of components in the compounds Fe: X: L is 1: 1: 1 without any exception. The measured optical properties (λ_max, ε_max) of the ternary chelates are discussed and compared with the corresponding binary iron(III) phenol chelate.     

Quantitative separation of gallium from zinc, copper, indium, iron(III) and other elements by cation-exchange chromatography in hydrobromic acid-acetone medium

Gallium can be separated from Zn, Cu(II), In, Cd, Pb(II), Bi(III), Au(III), Pt(IV), Pd(II), Tl(III), Sn(IV) and Fe(III) by elution of these elements with 0.50M hydrobromic acid in 80% acetone medium, from a column of AG50W-X4 cation-exchange resin. Gallium is retained and can be eluted with 3M hydrochloric acid. Separations are sharp and quantitative except for iron(III) which shows extensive tailing. With 0.20M hydrobromic acid in 80% acetone as eluting agent, all the species above except iron(III) and copper(II) can be separated from gallium with very large separation factors. Only a 1-g resin column and small elution volumes are required to separate trace amounts and up to 0.5 mmole of gallium from more than 1 g of zinc or the other elements. Hg(II), Rh(III), Ir(IV), Se(IV), Ge(IV), As(III) and Sb(III) have not been investigated, but should be separated together with zinc according to their known distribution coefficients. Relevant elution curves, results for the analysis of synthetic mixtures and for amounts of some elements remaining in the gallium fraction are presented.     

Finding the 3D structure of a molecule in its IR spectrum

 The labile iron(II) and iron(III) species are complexed directly in the sample solution with 1,10 phenanthroline and ferron (8-hydroxy-7-iodoquinoline-5-sulfonic acid), respectively. The complexes thus formed are mutually adsorbed and separated by solid phase extraction. The direct determination of iron(III) and iron(II) species with flame atomic absorption spectrometry (FAAS) follows the elution of the iron(III)-ferron complex adsorbed by an anion-exchange and an iron(II)-phenanthroline complex adsorbed by a non-polar RP-18 phase. In the case of indirect determination, the iron(II)-phenanthroline complex that passes through the anion-exchange phase, is measured, and the content of iron(III) is calculated by the difference of the iron(II) and the total iron content. A direct determination with this method has been applied to the iron species analysis in wine samples and the results are compared with those obtained for the determination with adsorptive stripping voltammetry (ASV) as reference method. Received: 17 August 1995/Revised: 12 February 1996/Accepted: 14 February 1996     

Application of the zone melting technique to metal chelate systems-II Concentration of a trace amount of metal acetylacetonate in chromium(III) acetylacetonate

The zone melting process was applied to tris(acetylacetonato) chromium(III) which contained a trace amount of aluminium(III), iron(III), copper(II), manganese(III), nickel(II) cobalt(III) and rhodium(III) in the forms of their acetylacetonates, and the highly purified chromium chelate was found in the top portion of a column, while the minor components except the rhodium chelate were concentrated in the bottom portion. The rhodium chelate was concentrated in the top portion. Ease of migration of the minor components during the zone melting process decreased in the order Cu, Fe, Mn, Co, Ni, Al and Rh, and was accounted for in terms of their crystal structures. Extremely slow speed of zone travel caused an increase of the distribution coefficient; this was due to back diffusion of minor components into a congealed solid phase from a molten zone.     

Chelating or bridging? Halide-controlled binding mode of diamido donor ligands in iron(III) complexes

In a series of iron(III) halide complexes of the form {FeX[MesN(SiMe(2))]2O}2 (Mes = mesityl; X = Cl, Br, I), the ancillary diamidosilylether ligand can either chelate to one metal or instead bridge two metal centers, as a function of the halide coligand. The complexes are prepared from diamidosilyletheriron(II) precursors, which are oxidized with iodine, benzyl bromide, or PhICl2 to yield the appropriate iron(III) halide. The bromide analogue can also be synthesized by reacting the iron(II) precursor with a bromonium transfer agent (stabilized by adamantylideneadamantane). The latter reaction may proceed via an iron(IV) intermediate, which can oxidize the normally noncoordinating, inert [B(ArF)4]- counteranion [ArF = 3,5-(CF3)2Ph].     

Self-assembly of tetrahedral and trigonal antiprismatic clusters [Fe4(L4)4] and [Fe6(L5)6] on the basis of trigonal tris-bidentate chelators

In a one-pot reaction, the tetranuclear iron chelate complex [Fe4(L4)4] 6 was generated from benzene-1,3,5-tricarboxylic acid trichloride (4), bis-tert-butyl malonate (5a), methyllithium, and iron(II) dichloride under aerobic conditions. Alternatively, hexanuclear iron chelate complex [Fe(L5)6] 7 was formed starting from bis-para-tolyl malonate (5b) by employing identical reaction conditions to those applied for the synthesis of 6. The clusters 6 and 7 are present as racemic mixtures of homoconfigurational (delta,delta,delta,delta)/(lambda,lambda,lambda,lambda)-fac or (delta,delta,delta,delta,delta,delta)/(lambda,lambda,lambda,lambda,lambda,lambda)-fac stereoisomers. The structures of 6 and 7 were unequivocally resolved by single-crystal X-ray analyses. The all-iron(III) character of 6 and 7 was determined by M?ssbauer spectroscopy.     

Ozonocatalytic decomposition of glyoxal and glyoxylic and formic acids in the presence of iron(III) ions

Rate constants of reactions of ozone with glyoxal, glyoxylic and formic acid in aqueous solutions at pH 1.5 were determined. It was shown that iron(III) in the form of ions accelerates oxidation of glyoxal and glyoxylic acid, but does not influence reaction between ozone and formic acid. It was established that the catalyst acts effectively if its concentration is comparable to the concentration of the oxidized substrate, the optimal stoichiometric ratio (Fe³⁺/substrate) being close to 1/3. The catalytic reaction mechanism was studied using a competitive chelate ligand, oxalic acid. We concluded that the catalytic activity of iron(III) in the investigated reaction was due to its ability to form chelate complexes in which the substrate was more easily oxidized by molecular ozone.     

Biomimetic hydrocarbon oxidation catalyzed by nonheme iron(III) complexes with peracids: evidence for an Fe(V)=O species

Mononuclear nonheme iron(III) complexes of tetradentate ligands containing two deprotonated amide moieties, [Fe(Me(2)bpb)Cl(H(2)O)] (3 a) and [Fe(bpc)Cl(H(2)O)] (4 a), were prepared by substitution reactions involving the previously synthesized iron(III) complexes [Et(3)NH][Fe(Me(2)bpb)Cl(2)] (3) and [Et(3)NH][Fe(bpc)Cl(2)] (4). Complexes 3 a and 4 a were characterized by IR and elemental analysis, and complex 3 a also by X-ray crystallography. Nonheme iron(III) complexes 3, 3 a, 4, and 4 a catalyze olefin epoxidation and alcohol oxidation on treatment with m-chloroperbenzoic acid. Pairwise comparisons of the reactivity of these complexes revealed that the nature of the axial ligand (Cl(-) versus H(2)O) influences the yield of oxidation products, whereas an electronic change in the supporting chelate ligand has little effect. Hydrocarbon oxidation by these catalysts was proposed to involve an iron(V) oxo species which is formed on heterolytic O-O bond cleavage of an iron acylperoxo intermediate (FeOOC(O)R). Evidence for this iron(V) oxo species was derived from KIE (k(H)/k(D)) values, H(2) (18)O exchange experiments, and the use of peroxyphenylacetic acid (PPAA) as the peracid. Our results suggest that an Fe(V)=O moiety can form in a system wherein the supporting chelate ligand comprises a mixture of neutral and anionic nitrogen donors. This work is relevant to the chemistry of mononuclear nonheme iron enzymes that are proposed to oxidize organic substrates via reaction pathways involving high-valent iron oxo species.