Complex-forming Agents Research Articles

Recovery of radionuclides with ionic liquids. I. Selective extraction of 241Am

1-methyl-3-octylimidazolium saccharinate {[C8C1im][Sac]} – a hydrophobic but polar ionic liquid (IL) capable of capturing and liberating water in a controllable manner was employed as an extraction phase in the liquid–liquid extraction for the recovery of radioactive elements (241Am, 137Cs and 60Co) from aqueous solutions. The influence of factors such as IL/aqueous source ratio, pH and presence of complex-forming agents (citric acid, oxalic acid) on the extraction yield was comprehensively studied. The radionuclides were shown to possess different behavior under the same conditions, the latter being attributed, and further proved by theoretical speciation analysis, to the formation of species capable of interacting in a specific manner with the IL-phase. The results obtained showed the possibility for controllable and selective transfer between the IL and aqueous phases and resulted in the development of a simple procedure for extraction and concentration of 241Am. The method developed proved successful in the monitoring of this radionuclide in drinking water samples.

Stabilization of unusual metal oxidation state +4 in the iron, cobalt, nickel, and copper complexes with trans-di[benzo]porphyrazine and two fluoride anions: a DFT quantum chemical analysis

Molecular structure calculations of heteroligand (6666)macrotetracyclic metal (MIV) chelates (M = Fe, Co, Ni, Cu) with trans-di[benzo]porphyrazine as the (N,N,N,N)-donor ligand and two F− anions were carried out at the OPBE/TZVP level of density functional theory. The key bond lengths, bond angles, and non-bond angles in the complexes were determined and corresponding standard enthalpies, entropies, and Gibbs energies of formation were calculated. All complexes have slightly distorted tetrahedral structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms. The metal—nitrogen bonds are usually pair-wise equal. The six-membered metal chelate rings in the complexes are identical to one another from the standpoint of both the sum and set of the bond angles.

3D printing of radioactive phantoms for nuclear medicine imaging

BackgroundFor multicenter clinical studies, PET/CT and SPECT/CT scanners need to be validated to ensure comparability between various scanner types and brands. This validation is usually performed using hollow phantoms filled with radioactive liquids. In recent years, 3D printing technology has gained increasing popularity for manufacturing of phantoms, as it is cost-efficient and allows preparation of phantoms of almost any shape. So far, however, direct 3D printing with radioactive building materials has not yet been reported. The aim of this work was to develop a procedure for preparation of 99mTc-containing building materials and demonstrate successful application of this material for 3D printing of several test objects.MethodThe desired activity of a [99mTc]pertechnetate solution eluted from a 99Mo/99mTc-generator was added to the liquid 3D building material, followed by a minute amount of trioctylphosphine. The resulting two-phase mixture was thoroughly mixed. Following separation of the phases and chemical removal of traces of water, the radioactive building material was diluted with the required volume of non-radioactive building material and directly used for 3D printing.ResultsUsing our optimized extraction protocol with trioctylphosphine as complex-forming phase transfer agent, technetium-99m was efficiently transferred from the aqueous 99Mo/99mTc-generator eluate into the organic liquid resin monomer. The observed radioactivity concentration ratio between the organic phase and the water phase was > 2000:1. The radioactivity was homogeneously distributed in the liquid resin monomer. We did not note differences in the 3D printing behavior of the radiolabeled and the unlabeled organic liquid resin monomers. Radio-TLC and SPECT studies showed homogenous 2D and 3D distribution of radioactivity throughout the printed phantoms. The radioactivity was stably bound in the resin, apart from a small amount of surface-extractable radioactivity under harsh conditions (ethanol at 50 °C).Conclusions3D printing of radioactive phantoms using 99mTc-containing building materials is feasible. Compared to the classical fillable phantoms, 3D printing with radioactive building materials allows manufacturing of phantoms without cold walls and in almost any shape. Related procedures with longer-lived radionuclides will enable production of phantoms for scanner validation and quality control.

HYDROPHOBIC ION-PAIRED DRUG DELIVERY SYSTEM: A REVIEW

Hydrophobic ion-pairing (HIP) complexation technique has been displayed to modify the physicochemical properties, solubility, oral absorption, bioavailability, and the lipophilicity of an ionic drug in the lipid phase. This could affect a higher permeation through biological membranes. HIP complexation was considered through the formation of a neutral molecule by electrostatic interaction of ionizable groups of drugs with oppositely charged functional groups of a complex-forming agent. Subsequently, this ion-pair may encapsulate into many delivery systems. The objective of this manuscript was to study the effectiveness of ion-pair complextion and cover the update application of this strategy through several routes of administration such as ocular, oral, pulmonary, transdermal, and parenteral.

Investigation of the kinetics and mechanism of low endotoxin recovery in a matrix for biopharmaceutical drug products

The inability to detect endotoxin added to undiluted drug samples has been called: Low Endotoxin Recovery (LER). The phenomenon has caused concerns amongst drug manufacturing quality control scientists in that manufactured solutions contaminated with endotoxin could show false-negative results via routine Limulus-based tests. The time-dependent appearance of LER has been analyzed in detail to provide a better understanding of the mechanism. The assumption has been that the root-cause of LER involves the interplay of endotoxin with surfactants and results in aggregate structures that are complexed with surfactants. The endotoxin molecules when complexed with surfactants are not accessible for Limulus-based detection. The results demonstrate a predominant role of complex-forming agents. It was shown that although the presence of surfactants is a strong prerequisite for masking, it does not determine the kinetics of endotoxin masking. Interestingly, the endotoxin concentration itself had no substantial impact on LER kinetics. By adjusting the ratios of complex-forming constituents, including surfactant, chelator and endotoxin, and by testing the order in which the constituents are added, a new model for simulating masking kinetics has been determined. Our work provides for the first time a model to simulate masking kinetics of endotoxin which lends a better understanding of LER.

Leaching of Waste Hydroxide Sludges by Complex-Forming Agents

<p>In the paper the problem of utilization of stale hydroxide sludges containing non-ferrous metals and arsenic is considered. It is proposed to carry out two-stage leaching of sludges by solutions of complexing agents with recovery of 97-99% of non-ferrous metals to solution and removal of arsenic in the form of sparingly soluble compounds suitable for burial.</p>

Aluminum hydroxocarboxylates in solution deposition of planarization alumina films

Aluminum hydroxocarboxylates derived from butyric, pivalic, valeric, and isovaleric acids were synthesized and characterized. The synthesized hydroxocarboxylates were suspended in isopropanol and reacted with diethylenetriamine and monoethanolamine, which acted as hydrolyzing and complex-forming agents, to obtain precursor solutions for chemical deposition of smooth amorphous alumina films on metal substrates.

Specifics of analysis of salt rocks from the Verkhnekamskoe deposit for Au, Pt, and Pd

The paper presents data on the possibility of ETAAS analysis, and a technique of this analysis, of salt rocks, their insoluble residues, and organic fractions from these rocks for Au, Pt, and Pd (concentrations from 10–7 to 10–2 ppm). Various techniques for the decomposition of the samples are discussed, and the paper presents information on the extent of Au, Pt, and Pd adsorption from chloride complexes when the POLYORGS-IV complex-forming adsorption agent is applied. The determined atomization parameters of the elements in a graphite furnace are reported. Precious metals are proved to be concentrated in the insoluble residues of the salt rocks and in the slimes (salt wastes) when the salt rocks are processed. The forms in which precious metals are contained in the salt-bearing rocks are determined.

Novel morphology change of Au-Methotrexate conjugates: From nanochains to discrete nanoparticles

A novel morphology change of Au-methotrexate (Au-MTX) conjugates that could transform from nanochains to discrete nanoparticles was achieved by a simple, one-pot, and hydrothermal growth method. Herein, MTX was used efficiently as a complex-forming agent, reducing agent, capping agent, and importantly a targeting anticancer drug. The formation mechanism suggested a similarity with the molecular imprinting technology. The Au–MTX complex induced the MTX molecules to selectively adsorb on different crystal facets of gold nanoparticles (AuNPs) and then formed gold nanospheres. Moreover, the abundantly binding MTX molecules promoted directional alignment of these gold nanospheres to further form nanochains. More interestingly, the linear structures gradually changed into discrete nanoparticles by adding different amount of ethylene diamine tetra (methylene phosphonic acid) (EDTMPA) into the initial reaction solution, which likely arose from the strong electrostatic effect of the negatively charged phosphonic acid groups. Compared with the as-prepared nanochains, the resultant discrete nanoparticles showed almost equal drug loading capacity but with higher drug release control, colloidal stability, and in vitro anticancer activity.

Unexpected catalytic activity of rhodium nanodendrites with nanosheet subunits for methanol electrooxidation in an alkaline medium

Nanocrystals of Rh, an important member of the noble metal catalyst family, have wide applications in heterogeneous catalytic reactions. Controlling the morphology of these noble metal nanocrystals has become an effective strategy for improving their catalytic activity and durability. In this work, well-defined Rh nanodendrites with very thin triangular branches as subunits are synthesized using a facile diethylene glycol reduction method, assisted by polyethyleneimine as a complex-forming agent and surfactant. For the first time, the methanol oxidation reaction (MOR) on Rh nanocrystals with a well-defined morphology is investigated using various electrochemical techniques in an alkaline medium. Unexpectedly, the as-prepared Rh nanodendrites, with ultrathin nanosheet subunits, exhibit superior electrocatalytic activity and durability during the MOR in an alkaline medium, indicating that Rh nanocrystals with specific morphology may be highly promising alternatives to Pt electrocatalysts in the MOR in an alkaline medium.

Adsorption study of mercury on lignite in the presence of different anions

Abstract This study compares the effect of different anions such as chloride, nitrate, and sulphate on the mercury adsorption onto lignite, which was a model material for the humus-containing organics in soil, and can be considered as a natural sorbent in the remediation of contaminated sites. Since the complex formation can significantly influence the mercury sorption, besides chloride, the effects of other complex-forming agents such as ethylenediaminetetraacetic acid, and thiocyanate were also tested. Various batch type and dynamic experiments were performed and four sorption models (Langmuir, Freundlich, Temkin and Dubinin-Radushkevich) were used to evaluate the sorption data.

Sorption of trace elements on xylain: An experimental study

Sorption and desorption of Sr, Mn, Co, Ni, Cu, and Zn on xylain from lignites of the Mariza-East coal basin (Bulgaria) were studied. Sorption behaviour for all the studied elements was found to be of similar pH dependence for all elements. The maximum quantities bound vary from 0.104meq (Sr) to 0.167meq for Cu. On treatment with a complex-forming agent such as tartaric acid, a high degree of extraction was achieved. However, appreciable amounts of elements remain tightly bound on the sorbent. When present simultaneously in solution, the quantity of every element sorbed, excluding Cu, is lower as compared with the quantities from the experiments for single cations. The cation-exchange mechanism of the sorption and formation of covalent links was determined. Such processes may be responsible for part of the organically-associated elements in coals in case they are influenced by solutions enriched in some trace elements.

Preparation for Pt-Loaded Zeolite Catalysts Using w/o Microemulsion and Their Hydrocracking Behaviors on Fischer-Tropsch Product

Pt-loaded β-type zeolite catalysts with constant Pt content (0.11 wt.%) and similar pore structure were prepared using a water-in-oil (w/o) microemulsion. The effect of Pt particle synthesis conditions using microemulsion (a type of Pt complex-forming agents and the molar ratio of complex-forming agent to Pt4+) on loaded Pt particle size was investigated. The Pt particle size of the Pt catalyst using tetraethylammonium chloride (TEAC) as a complex-forming agent with the molar TEAC/Pt ratio 10 was the minimum value (3.8 nm), and was much smaller than that (6.7 nm) prepared by the impregnation method. The utilization of the complex-forming agent of which hydrophobic groups occupied a small volume and the appropriate complex-forming agent/Pt ratio were favorable for synthesis of small Pt particles. The effect of loaded Pt particle size on the hydrocracking of the Fischer-Tropsch (FT) product was investigated using the Pt-loaded zeolite catalysts at 250 °C with an initial H2 pressure of 0.5 MPa, and reaction time of 1 h. The Pt catalyst with a Pt particle size of 4.2 nm prepared using the microemulsion exhibited the maximum corresponding jet fuel yield (30.0%), which was higher than that of the impregnated catalyst.

Electrolytic preparation of nanosized Cu/Ni–Cu multilayered coatings

AbstractThe electrolytic deposition of nanosized Cu/Ni-Cu multilayer coatings on a paraffin-impregnated graphite substrate was performed from an electrolyte consisting of sulphate salts of the above metals and a complex-forming agent, sodium citrate. The multilayer Cu/Ni-Cu coatings were prepared using the potentiostatic method, in which the potential was alternately pulsed between the reduction potentials of the components. Suitable deposition potentials were selected from the polarisation curves. The presence of the thin films was confirmed by atomic absorption spectroscopy (after dissolution) and by optical microscopy. The resulting images show a layered structure of Cu/Ni-Cu coatings formed by Cu, Ni and/or Ni-Cu layers.

Study of molecular complexation of glycyrrhizic acid with chloramphenicol by electrospray ionization mass spectrometry.

Context:Glycyrrhizic acid (GA) is a triterpene glycoside representing the main active component of licorice root extract obtained from plants of the Glycyrrhiza glabra L. and widely used as a complex-forming agent for the synthesis of new transport forms of the well-known drugs.Aims:For the first time, the complexation of GA with chloramphenicol antibiotic (ChlA) was investigated by electrospray ionization mass spectrometry (ESI MS).Subjects and Methods:ESI MS was utilized in order to determine the composition and evaluate the stability of complexes of the GA and ChlA. The validation of the complex formation was confirmed by ultraviolet/visible and infrared (IR) spectroscopy.Results:MS data confirmed the noncovalent interactions between chloramphenicol and GA. Formation of the host: guest complexes of GA and chloramphenicol with the ratio 1:1 and 2:1 were registered in the negative ion mode. Binding of GA and ChlA was accompanied by changes in absorbance and IR spectrum of ChlA indicating the complex formation of these compounds.Conclusions:The research results confirmed the considerable potential of ESI MS as a technique for simple and fast detection of formation of the complexes of GA and the well-known drugs.

Processes involved in sweeping as sample enrichment method in cyclodextrin‐modified micellar electrokinetic chromatography of hydrophobic basic analytes

Sweeping is an enrichment method in MEKC, which includes following steps: stacking/destacking of the micelles, sweeping of analyte by the stacked/destacked micelles, destacking/stacking of the swept analyte zone and additional focusing/defocusing due to the retention factor gradient effect (RFGE). In this study, we investigate additional processes, regarding online focusing in cyclodextrin-modified MEKC (CD-MEKC) of hydrophobic basic analytes: dynamic pH junction (sample with pH different from that of BGE) and adsorption of analyte onto the capillary wall within the sample zone. It is demonstrated that the developed method for the assessment of the sweeping efficiency is also applicable to CD-MEKC taking ethylparaben as an example of acidic analytes and desloratadine as an example of basic analytes using different types of β-cyclodextrin. Our previous results regarding RFGE as an additional focusing/defocusing effect in sweeping-MEKC are confirmed for the case that the apparent distribution coefficient differs for the sample and the BGE due to a different content of the complex-forming agent cyclodextrin and due to a pH difference between the sample and the BGE. Despite being significantly more hydrophobic than ethylparaben, desloratadine shows an unexpectedly low enrichment factor. This enrichment factor is nearly unaffected by the addition of CD to the BGE. This unexpected behavior is attributed to wall adsorption of the protonated hydrophobic basic analyte within the sample zone, which significantly counteracts the sweeping process. This assumption is corroborated by an improvement in the enrichment factor achieved via addition of a dynamic coating agent (triethylamine) to the sample solution.

Facile water-based synthesis and catalytic properties of platinum–gold alloy nanocubes

Controlled syntheses of noble metal based alloy nanocubes with {100} facets have attracted increasing attention due to their specific physical and chemical properties. This paper reports a facile, green and one-pot synthesis of platinum–gold alloy nanocubes (Pt–Au ANCs) with high yield and uniform size by a facile co-chemical reduction method. The detailed morphology, composition and structure of Pt–Au ANCs were fully characterized and their formation mechanism was investigated. The key synthesis strategy was the introduction of polyallylamine hydrochloride (PAH), which not only acted as a capping agent and facet-selective agent but also served as a complex-forming agent to effectively tune the reduction potentials of HAuCl4/Au and H2PtCl6/Pt pairs to very close values. In addition, the as-prepared Pt–Au ANCs possessed excellent colloidal stability in aqueous solution and exhibited superior catalytic activity toward the reduction of 4-nitrophenol (4-NP) compared to commercial Pt black.

Polyallylamine Functionalized Palladium Icosahedra: One-Pot Water-Based Synthesis and Their Superior Electrocatalytic Activity and Ethanol Tolerant Ability in Alkaline Media

Polyallylamine (PAH) functionalized Pd icosahedra are synthesized through a simple, one-pot, seedless and hydrothermal growth method. Herein, PAH is used efficiently as a complex-forming agent, capping agent, and facet-selective agent. The strong interaction between PAH and Pd atom sharply changes the electronic structure of Pd atom in the Pd icosahedra. The protective function of PAH layers and enhanced antietching capability of Pd atom are responsible for the formation of the Pd icosahedra. Very importantly, the as-prepared PAH functionalized Pd icosahedra exhibit superior electrocatalytic activity and ethanol tolerant ability toward the oxygen reduction reaction (ORR) compared to the commercially available Pt black in alkaline media. At 0.95 V (vs RHE), the ORR specific kinetic current density at the Pd icosahedra is 4.48 times higher than that at commercial Pt black. The fact demonstrates the appropriate surface modification of the Pd nanoparticles by nonmetallic molecules can be regarded as an effective way to enhance the electrocatalytic activity toward the ORR.

Numerical simulation and experiment in the systems of labile complexes of metals. Silver reduction from the thiourea electrolyte

Voltammograms of silver reduction from complex thiourea electrolytes with the ligand to metal concentration ratio varied from 1 to 50 were measured on the freshly prepared surface of silver electrode. The results were analyzed using the numerical model of this electrode process which takes into account homogeneous chemical reactions proceeding in solution, diffusion–migration transfer of the species present in solution, and electrode reactions participated by electroactive components of the electrolyte. We estimated the values of standard exchange current density for partial electrode reactions in which silver complexes with different number of ligands can take part. The highest electrochemical activity is exhibited in solutions with the low concentration of complex-forming agent – by silver aqua complexes, while in solutions with high thiourea concentration – by silver complexes with one ligand. It was found that kinetic hindrances to discharge of the thiourea silver complexes unlikely to be due to the adsorption of thiourea molecules blocking the growth sites or to the adsorption of complex silver ions. The results admit interpretation of the mechanism of electrode process either from the viewpoint of simultaneous discharge of all the complex silver ions present or from the viewpoint of discharge of silver complex with one ligand in combination with rapid chemical reactions of dissociation of other, non-discharging silver complexes.

Polyallylamine-directed green synthesis of platinum nanocubes. Shape and electronic effect codependent enhanced electrocatalytic activity

The synthesis of Pt nanocrystals with controlled size and morphology has drawn enormous interest due to their particular catalytic activity. We present a facile and green hydrothermal method for synthesizing monodisperse Pt nanocubes (Pt-NCs) with polyallylamine hydrochloride (PAH) as a complex-forming agent, capping agent and facet-selective agent, and formaldehyde as a reductant. The formation mechanism, particle size and surface composition of the Pt-NCs were investigated by Ultraviolet and visible spectroscopy (UV-vis), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), etc. In the proposed PAH-K(2)PtCl(4)-HCHO synthesis system, the raw material could be reutilized to re-synthesize the Pt-NCs, and the particle size of the Pt-NCs could be readily controlled by the reduction rate of the Pt(II) species in the Pt(II)-PAH complex. After UV/Ozone and electrochemical cleaning, the residual PAH on the Pt-NC surfaces still strongly influenced the d-band centre of Pt due to the strong N-Pt interaction. The as-prepared 6 nm Pt-NCs showed superior electrocatalytic activity (mass activity and specific activity) and stability towards the oxygen reduction reaction (ORR) in both H(2)SO(4) and HClO(4) electrolytes compared to the commercial E-TEK Pt black, owing to the combination of the facets effect and electronic effect.