Acid-base properties of the surface of chromatographic sorbents modified by metal acetylacetonates

The acid-base properties of metal acetylacetonates and chromatographic sorbents on the basis of Chromaton N with deposited combined stationary phases from polyethylene glycol (PEG 20M) and nickel(II) and iron(III) acetylacetonates have been investigated by means of pH measurement and Hammett indicator adsorption. The change of the acid-base state of the surface of Chromaton N depending on the nature of a metal of the modifying additive, the complex structure, and the deposition method has been demonstrated.     

Determination of Metal Traces in Polypropylene by Gas Chromatography

A procedure was developed for determination of metal traces in polypropylene on chromatographic sorbents and phases of various polarities. The thermal stability of volatile aluminum, chromium, and gallium acetylacetonates under the conditions of gas chromatography was studied. The influence exerted on the determination process by the column material, temperature, and polarity of phases was examined.     

Studies of adsorption and solution of acetylacetonates of Cr(III), Co(III) and Al(III) by gas chromatography

Summary Specific retention volumes, adsorption isotherms, molar heats of solution and changes of the entropy were determined from chromatographic data, which was obtained by the gas chromatographic separation of metal acetylacetonates. The retention data for Cr(III), Co(III) and Al(III) acetylacetonates were measured at different temperatures and different flow rates. From the retention data other values associated with adsorption and solution phenomena were calculated.     

Chelating Sorbents Prepared by the Modification of Silica Gel, Lichroprep RP-8 and Lichroprep RP-18 with Calcon and Their Application in the Analysis of Some Metal Ions

 Two new chelating sorbents for metal ions were prepared by the impregnation of chemically modified silicas LiChroprep RP-8 and RP-18 with ion pairs composed of the cation of Aliquat 336 and the anion of Calcon. The sorbents were compared with an analogous sorbent with a plain silica carrier containing the same ion pairs. A hypothesis for binding this ion pair by the surfaces of the applied carriers was presented. A higher stability of the two sorbents in comparison with that of the plain silica chelating sorbent was demonstrated. The sorbents obtained were applied for chromatographic separations of some chosen mixtures of some metal ions and for additional purification of aqueous solutions of alkali metals from trace amounts of heavy metals. The multiple use of the sorbents based on RP-8 and RP-18 in sorption–desorption processes of metal ions without deterioration of their sorption capacities was demonstrated. Received March 8, 2000. Revision March 5, 2001.     

3-R-Thio- and 3-R-Oxy-substituted metal acetylacetonates

New S- and O-substituted metal acetylacetonates were prepared from phenylthio-, butylthio-, benzenesulfonato-, and 3-acetoxyacetylacetone and appropriate metal salts. The spectral characteristics of the compounds were obtained. The effect of the α-substituent on the stability of the chelates under the conditions of chromatographic separation on silica gel was revealed. The reactivity of the acetate group bonded to the chelate ring is decreased, which does not allow preparation of new substituted complexes by common transformations of esters.     

An application of the coincidence Doppler spectroscopy for substances of chemical interest: phthalocyanine and acetylacetonate complexes

Coincidence Doppler spectroscopy, which is particularly powerful when one is concerned with high momentum components of positron annihilation gamma-rays, has been applied to two different kinds of organo-metalic ligands: metal phthalocyanines and metal acetylacetonates. The energy (momentum) profiles of the annihilation gamma-rays were the same for metal phthalocyanines indicating that positron and/or positronium are not interacting with the metal ions. However, the profiles for the metal acetylacetonates evidently showed a dependence on the kind of metal ions. Discussion is made on the features of positron interaction which are different for phthalocyanines and acetylacetonates.     

Synthesis and investigation of organosilicon dendrimers based on octavinylsilsesquioxane and sulfenyl chlorides of metal acetylacetonates

The addition of sulfenyl chlorides of metal acetylacetonates to octavinylsilsesquioxane was studied. The addition was shown to proceed at four of the eight vinyl groups of the octavinylsilsesquioxane, without the formation of cross-linked polymers. This allowed us to synthesize with high yields new non-functianalized and functianalized dendrimers based on octavinylsilsesquioxane and the sulfenyl chlorides of metal acetylacetonates.     

Fractional sublimation of various metal b-diketone chelates

The vacuum fractional sublimation of various metal β-diketone chelates was compared with the fractional sublimation of the metal acetylacetonates reported earlier. Characteristic recrystallization temperature zones are reported for a number of metal acetylacetonates, acetyltrifluoroacetonates, hexafluoroacetylacetonates, benzoylacetonates, and benzoyltrifluoroacetonates. The substitution of a trifluoromethyl for a methyl group in the ligand molecule increased the volatility of the corresponding metal chelates, but this increased volatility did not lead to improved separations by fractional sublimation. In particular, the hexafluoroacetylacetonates tended to recrystallize as microcrystals in diffuse zones which extended over much of the sublimation tube and the benzoyltrifluoroacetonates tended to distill rather than sublime, with the liquids flowing down the wall of the tube. The best separations were achieved among the metal acetylacetonates. The chelates studied are generally stable and can be recovered from the sublimation apparatus in near quantitative yields. Separations of mixtures of Be, Mg, and Cr ; Fe, Mg and Al ; and Fe and Al were studied critically. Although the separations were not complete, they compared favorably with some reported gas-chromatographic separations.     

Emerging materials for sample preparation

This review provides an update on the implementation of emerging materials as sorbents for sample preparation in combination with chromatographic separation. We have focused on recent applications of metal–organic frameworks, layered double hydroxides, porous carbons obtained from polymers or biomass precursors, and silicates (clays and zeolites). The review is directed toward the strategies followed by the authors to engineer suitable supports enabling the application of materials with unconventional size and shape as high‐performance sorbents to explore new boundaries in sample pretreatment in manual or automated modes.     

The microdetection of particulates from organometallic compounds : I. Metal acetylacetonate chelates

The new technique of organic particulate analysis (OPA) has been employed to evaluate the thermal decomposition of metal acetylacetonate chelates. Of the 23 compounds thus evaluated, 13 were found to give organoparticulation signals at temperatures <190 °C as indicated by their effect on the output current of an ion chamber detector. In some instances, very strong particulation was observed, particularly with the transition metal acetylacetonates, such as Co(II), Co(III), Fe(III), Cr(III), and Mn(III).In an attempt to characterize the nature of the particulates derived from these compounds, mass-spectral data were obtained on the effluent species arising from the thermal decompositions of the strongest particulate emitting metal acetylacetonates. The results showed that acetylacetone was the major component identified in both particulate and vapor effluents. With the exception of Cr(III) acetylacetonate, no metal was detected in these effluents.The OPA technique enabled the relative thermal stabilities of the metal acetylacetonates to be ascertained. Zn acetylacetonate was found to have the lowest thermal stability and the alkaline earth compounds the highest; the transition metal acetylacetonates exhibit intermediate thermal stabilities.Since a certain critical minimum particulate size (i.e., 25 Å) seems to be necessary to produce a response on the ion chamber detector instrument, vapor-phase association of acetylacetone molecules may be occurring. This association would most probably occur through H-bonded species involving the enol form of the 1,3-diketone.     

Facile synthesis and reactions of some olefin-substituted acetylacetonate complexes

Synthesis of transition metal complexes of olefin-substituted acetylacetones has been effected by reaction of nonaqueous solutions of substituted acetylacetones with the metal salt in the presence of Zn or Mg. 3-Allylacetylacetonates of Be(II), Cu(II), Ni(II), Fe(III), Co(II), Pd(II) and Zn(II) have thus been synthesized in quantitative yields. 3-Propylideneacetylacetone, which exists mainly in the keto form, afforded the corresponding 3-propenylacetylacetonates in which 3-propylideneacetylacetone has rearranged to 3-propenylacetylacetone which has a greater probability of existing in the enol form, thus making its reaction with metal ions favorable. Metal–metal exchange reactions of transition metal salts with olefin-substituted Zn or Mg acetylacetonates provide yet another route for the synthesis of transition metal olefin-substituted acetylacetonates. The homogeneous catalytic hydrogenation of the olefin moiety in olefin-substituted metal acetylacetonates could be achieved by a Pt/Sn catalyst.     

Evaluation of metal fractions in river sediments and waters: application of chelation chromatography-differential pulse anodic stripping voltammetry

The ability of chelation chromatography in combination with differential pulse anodic stripping voltammetry (DPASV) to provide a simple, fast and reliable way of dealing with interionic interferences, competitive complexations, re-adsorption of released metal ions and sorption of spiking metal ions by organic/inorganic materials in the complex matrixes of real natural samples has been critically examined. The technique is based on the selective complexation of target metal fractions on some novel sorbents which are polymeric chelating resins doped on stationary supports (Whatman No. 1 paper and silica gel). The usual complications of leaching of the resin and/or the chelating ligand and colloid retention on the sorption bed at any stage of separation were largely obviated with these sorbents under the operational conditions of metal sorption. A detailed study on the application of such sorbents to the differentiation of ionic (free), labile (ionic plus weakly complexed) and bound (strongly complexed) metal fractions present in local river-sediment and water samples was carried out. Chelating resin-impregnated paper (CRIP) and chelating resin-immobilized silica gel column (CRISC) methods of chromatographic separation of analyte trace metals in combination with the follow-up 'standard addition' procedure of the DPASV technique were employed. A modest attempt has been made to formulate a speciation (fractionation) scheme for metal contents present in river-sediments and waters on the basis of selective retention of ionic and labile fractions on complexing resins.     

Solvent effects in gel chromatography: the relationship between the distribution coefficients of metal acetylacetonates and solubility parameters of solvents

Distribution coefficients of metal acetylacetonates such as Al(acac)₃, Cr(acac)₃ and Co(acac)₃ etc., and n-alkanes in porous polystyrene gel chromatography with ten organic solvents as eluants were estimated and compared with those obtained by the batch method in two solvent systems. Solubility parameters of the metal acetylacetonates were determined. There is a relationship between the distribution coefficients and solubility parameters of solutes and solvents. Two factors (steric exclusion and partition) play important rôles in each solvent for the separation mechanisms of the present systems. The latter factor was estimated successfully from a regular solutions approximation.     

Separation of actinides from Low Level Liquid Wastes (LLLW) by extraction chromatography using novel DMDOHEMA and TODGA impregnated resins

The uptake of several actinides [U(VI), Th(IV), Am(III), Cm(III)] and fission products was investigated from nitric acid solutions by two novel extraction chromatographic sorbents containing 2-(2-hexyloxy-ethyl)-N,N'-dimethyl-N,N'-dioctyl-malonamide (DMDOHEMA) and N,N,N',N'-tetraoctyl-3-oxapentane-1,5-diamide (TODGA), respectively. The kinetics of the uptake of actinides was studied. The sorption of metal ions fromz simulated Low Level Liquid Waste (LLLW) solutions was evaluated. The results of these experiments revealed that the actinides and lanthanides could be separated from the bulk of other fission products in simulated LLLW solutions on both sorbents.This revised version was published online in November 2005 with corrections to the Cover Date.     

High-Performance Chelation Chromatography of Metal Ions on Sorbents with Grafted Iminodiacetic Acid

The chromatographic behavior of some alkaline-earth, transition, heavy, and rare-earth metals on a number of complexing sorbents containing surface iminodiacetic acid (IDA) functional groups is studied. The conditions under which metal retention is determined by complexation on the sorbent surface were established, and the main principles of a new variant of the liquid chromatography, i.e., high-performance chelation ion chromatography (HPCIC), are formulated. The efficiency and selectivity of separation of the metal ions are considered depending on the type of the IDA bonding, the sorbent matrix parameters, the eluent composition, and the temeprature of the chromatographic column. Under optimal conditions, the metal retention is shown to linearly correlate with the stability constants of the respective complexes in the double-logarithmic scale. The application of HPCIC to the analysis of multicomponent systems is considered.     

Anion chromatography on hydroxyethyl methacrylate-based sorbents

The selectivity of sorbents plays an important role in the design of ion chromatographic separations. The selectivity of the hydroxyethylmethacrylate-based sorbent Tessek Separon HEMA-S 1000 Q-L was compared with those of other commonly used sorbents and the role of the eluent charge was investigated. The selectivity of this sorbent was found to be satisfactory for most commonly used ion chromatographic detection modes, including indirect photometry and both suppressed and non-suppressed conductivity detection.     

One-minute synthesis of crystalline binary and ternary metal oxide nanoparticles

Highly crystalline metal oxide nanoparticles such as CoO, ZnO, Fe(3)O(4), MnO, Mn(3)O(4), and BaTiO(3) were synthesized in just a few minutes by reacting metal alkoxides, acetates or acetylacetonates with benzyl alcohol under microwave heating.     

Thermodynamics of complex formation reactions between d metals and linear oligopyrroles

The interaction of alkyl-substituted α,α-dipyrrolylmethenes with d metal acetates and acetylacetonates was studied by spectrophotometric and calorimetric titration methods. The thermodynamics of complex formation reactions between d metal ions and dipyrrolyl ligands was found to depend on the entropy and enthalpy contributions, the nature of a metal, and on the solvation factors.     

Metal acetylacetonate domains grown on H-terminated porous silicon at room temperature and their specific I-V behavior

Porous silicon (PS) was incubated in an organic solution of metal acetylacetonates of Mn(acac)(3), Fe(acac)(3), Co(acac)(3), and Ni(acac)(2) (acac = MeCOCHCOMe) at room temperature. Crystal-like domains were found to be spontaneously self-assembled on PS surfaces by atomic force microscopy (AFM). Spectroscopic studies with attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) revealed that the domains were grown from metal acetylacetonates. Current sensing atomic force microscopy (CSAFM) was used to measure the I-V curves of domains in nanoscale and specific step-jump currents on the manganese and cobalt acetylacetonate domains were surprisingly detected.     

Nitrogen-containing heterocycles from metal β-diketonates

Factors determining the reaction of metal β-diketonates with hydrazine, in particular the nature of central metal ion and structure of β-diketonate ligand, are discussed. The possibility for the preparation of other heterocyclic compounds via reaction of metal acetylacetonates with phenylhydrazine, o-phenylenediamine, urea, and thiourea was studied.