Ionic liquid-functionalized silica for selective solid-phase extraction of organic acids, amines and aldehydes

Capture of aqueous radioiodine species by metallated adsorbents from wastestreams of the nuclear power industry: a review

Abstract

Iodine-129 poses a significant challenge in the drive towards lowering radionuclide emissions from used nuclear fuel recycling operations. Various techniques are employed for capture of gaseous iodine species, but it is also present, mainly as iodide anions, in problematic residual aqueous wastestreams, which have stimulated research interest in technologies for adsorption and retention of the radioiodine. This removal effort requires specialised adsorbents, which use soft metals to create selectivity in the challenging chemical conditions. A review of the literature, at laboratory scale, reveals a number of organic, inorganic and hybrid adsorbent matrices have been investigated for this purpose. They are functionalised principally by Ag metal, but also Bi, Cu and Pb, using numerous synthetic strategies. The iodide capacity of the adsorbents varies from 13 to 430 mg g−1, with ion-exchange resins and titanates displaying the highest maximum uptakes. Kinetics of adsorption are often slow, requiring several days to reach equilibrium, although some ligated metal ion and metal nanoparticle systems can equilibrate in < 1 h. Ag-loaded materials generally exhibit superior selectivity for iodide verses other common anions, but more consideration is required of how these materials would function successfully in industrial operation; specifically their performance in dynamic column experiments and stability of the bound radioiodine in the conversion to final wasteform and subsequent geological storage.

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Progress in pretreatment and analysis of organic Acids: An update since 2010

Organic acids, as an important component of food, have great influence on the flavor, texture, freshness of food. By lowering the pH of food to bacteriostatic acidity, organic acids are also used as additives and preservatives. Because organic acids are crucial to predict and evaluate food maturity, production and quality control, the rapid and sensitive determination methods of organic acids are necessary. This review aims to summarize and update the progress of the determination of organic acids in food samples. Pretreatment methods include simple steps (e.g., "dilute and shoot," protein precipitation, filtration, and centrifugation) and advanced microextraction methods (e.g., hollow fiber liquid phase microextraction, stir bar sorptive extraction and dispersive micro-solid phase extraction). Advances in novel materials (nanomaterial), solvents (ionic liquids and supercritical fluids) and hybrid methods are clearly displayed in detail. Continuous progress which has been made in electrochemical method, two-dimensional chromatography, high resolution mass is thoroughly illustrated.

Extraction of β-blockers from urine with a polymeric monolith modified with 1-allyl-3-methylimidazolium chloride in spin column format

A glycidyl methacrylate-based monolith was modified with imidazolium-based ionic liquid (IL) to be used as stationary phase for solid-phase extraction (SPE). The host monolithic support was prepared by in-situ UV polymerization in spin column format. Two approaches were developed to incorporate the IL into the polymeric monolithic matrix: generation of IL onto the surface monolith, and copolymerization by addition of the IL to the polymerization mixture, which gave the best results. The resulting sorbent materials were morphologically characterized and used for the isolation of five β-blockers from human urine samples. All SPE steps were accomplished by centrifugation, which reduces significantly costs and time in sample treatment. Under optimal conditions, β-blockers were quantitatively retained in the modified monolith at pH 12, and desorbed with a water-methanol mixture, to be subsequently determined via HPLC with UV detection. The limits of detection ranged between 1.4 and 40 μg L^-1, and the reproducibility among extraction units (expressed as relative standard deviation) was below 8.2%. The novel phase was successfully applied to the extraction of propranolol in urine samples with recoveries above 90%.

Synthesis of a crosslinked poly(ionic liquid) and evaluation of its antimony binding properties

First ever ionic liquid derived sorbent for antimony was synthesised. The charged functional groups of the polymer showed preferential binding and strong affinity for difficult to remove anionic species of antimony. The sorbent was synthesised by crosslinking co-polymerisation of 1-butyl-3-vinylimidazolium bromide with N,N-methylenebis(acrylamide). SEM-EDS analysis showed that the polymer retained the bromide counter ions. Antimony removal properties under wide solution conditions, including the presence of competitor ions, were investigated. Maximum antimony binding and selectivity was at pH 3.0. Variation in saturation capacity with respect to the crosslinker amount matched with the calculated capacity values. Maximum uptake obtained was 4.6 and 3.2 mmol/g for Sb(III) and Sb(V) respectively. Tartrate salt of Sb(III) showed better binding through the interaction of tartrate with the imidazole moieties of the polymer. In less than 15 min, saturation capacity was achieved for Sb(III), while over 90% of uptake was complete for Sb(V). Investigations on sorption mechanism, which included synthesis and comparative evaluation of the non-ionic counterpart polyvinylimidazole as sorbent, indicated the uptake to be through anion exchange. Sb(III) specific binding against Sb(V) was seen in the presence of nitrilotriacetic acid.

Aldehydes as Wort Off-Flavours in Alcohol-Free Beers—Origin and Control

Although present in concentrations in microgrammes per litre level, aldehydes, in particular those derived from Strecker degradation, are known to majorly contribute to the undesired wort flavour of alcohol-free beers. In order to improve currently available products, one needs to understand the underlying cause for the over-prevalence and identify leverage points and methods to selectively reduce the aldehydes in alcohol-free beers. This work gives a short overview on relevant flavour-active wort flavours identified in alcohol-free beer and on their involved chemical formation pathways. Consequently, aldehyde removal technologies in general and in brewing industry are presented. Adsorptive removal of off-flavours by aldehyde-scavenging groups is already widely exploited in the packaging industry and may achieve reduction of these components to near depletion, depending on the process conditions. Its principles are adaptable to recovering off-flavours before filling. Also, supercritical CO2 extraction has been successfully applied to separate flavours from food matrices. In brewing, the focus has been set to biologic conversion by restricted fermentation steps, but the reduction of key components of more than 70% is not achieved. Newer developments focus on thermal separation techniques that not only include non-specific physical dealcoholisation but also more selective technologies such as pervaporation, where aldehydes are reduced to near depletion. However, for most unit operations, selectivity and capacity are not yet investigated. Future research should explore the shortcomings of current techniques and overcome bottlenecks either by developing more specific methods for aldehyde removal and/or a clever combination of unit operations to optimise the separation and process integration.

Fundamental Properties of Packing Materials for Liquid Chromatography

The high performance of chemically-modified silica gel packing materials is based on the utilization of pure silica gels. Earlier silica gels used to be made from inorganic silica; however, nowadays, silica gels are made from organic silanes. The surface smoothness and lack of trace metals of new silica gels permits easy surface modifications (chemical reactions) and improves the reproducibility and stability. Sharpening peak symmetry is based on developing better surface modification methods (silylation). Typical examples can be found in the chromatography of amitriptyline for silanol testing and that of quinizarin for trace metal testing. These test compounds were selected and demonstrated sensitive results in the measurement of trace amounts of either silanol or trace metals. Here, we demonstrate the three-dimensional model chemical structures of bonded-phase silica gels with surface electron density for easy understanding of the molecular interaction sites with analytes. Furthermore, a quantitative explanation of hydrophilic and hydrophobic liquid chromatographies was provided. The synthesis methods of superficially porous silica gels and their modified products were introduced.

Isolation, Separation, and Preconcentration of Biologically Active Compounds from Plant Matrices by Extraction Techniques

Development of efficient methods for isolation and separation of biologically active compounds remains an important challenge for researchers. Designing systems such as organomineral composite materials that allow extraction of a wide range of biologically active compounds, acting as broad-utility solid-phase extraction agents, remains an important and necessary task. Selective sorbents can be easily used for highly selective and reliable extraction of specific components present in complex matrices. Herein, state-of-the-art approaches for selective isolation, preconcentration, and separation of biologically active compounds from a range of matrices are discussed. Primary focus is given to novel extraction methods for some biologically active compounds including cyclic polyols, flavonoids, and oligosaccharides from plants. In addition, application of silica-, carbon-, and polymer-based solid-phase extraction adsorbents and membrane extraction for selective separation of these compounds is discussed. Potential separation process interactions are recommended; their understanding is of utmost importance for the creation of optimal conditions to extract biologically active compounds including those with estrogenic properties.

Simultaneous extraction and HPLC determination of 3-indole butyric acid and 3-indole acetic acid in pea plant by using ionic liquid-modified silica as sorbent

In this study, ionic liquid-modified silica was used as sorbent for simultaneous extraction and preconcentration of 3-indole butyric acid and 3-indole acetic acid in pea plants. The effect of some parameters such as pH and ionic strength of sample solution, amount of sorbent, flow rate of aqueous sample solution and eluent solution, concentration of eluent solution, and temperature were studied for each hormone solution. Percent extraction of 3-indole butyric acid and 3-indole acetic acid was strongly affected by pH of aqueous sample solution. Ionic strength of aqueous phase and temperature showed no serious effects on extraction efficiency of studied plant hormones. Obtained breakthrough volume was 200mL for each of studied hormones. Preconcentration factor for spectroscopic and chromatographic determination of studied hormones was 100 and 4.0×10(3) respectively. Each solid sorbent phase was reusable for almost 10 times of extraction/stripping procedure. Relative standard deviations of extraction/stripping processes of 3-indole butyric acid and 3-indole acetic acid were 2.79% and 3.66% respectively. The calculated limit of detections for IBA and IAA were 9.1×10(-2)mgL(-1) and 1.6×10(-1)mgL(-1) respectively.

Synthesis of core–shell imprinting polymers with uniform thin imprinting layer via iniferter-induced radical polymerization for the selective recognition of thymopentin in aqueous solution

Core–shell imprinting microspheres for the selective and rapid recognition of thymopentin with the aid of a novel polymeric ionic liquid.

Immobilized chiral tropine ionic liquid on silica gel as adsorbent for separation of metal ions and racemic amino acids

Tropine-type chiral ionic liquid with proline anion was immobilized on silica gel by chemical modification method for the first time, which was proved by elemental, infrared spectrum and thermogravimetric analysis. Secondly, the performance of this kind of ionic liquid-modified silica gel was investigated in the adsorption of some metal ions, which included Cu(2+), Fe(3+), Mn(2+) and Ni(2+). Then the effects of time, initial concentration and temperature on adsorption for Cu(2+) ions were studied in detail, which was followed by the further research of adsorption kinetics and thermodynamics. The adsorption could be better described by pseudo-second-order kinetics model and that the process was spontaneous, exothermic and entropy decreasing. In the mode of 'reuse after adsorption', the ionic liquid-modified silica gel with saturated adsorption of Cu(2+) was finally used in resolution of racemic amino acids for the first time. The static experiment showed that adsorption rate of two enantiomers was obviously different. Inspired by this, the complex was packed in chromatographic column for the separation of racemic amino acids and d-enantiomers were firstly eluted by water or ethanol. Steric hindrance was found as one of key influencing factors for its effect on the stability of the complex.

Extraction and Recovery of Naphthenic Acid from Acidic Oil Using Supported Ionic Liquid Phases (SILPs)

In this study, functionalized silica supported ionic liquids phases (SILPs) were synthesized and characterized using Fourier Transform infrared (FTIR) spectroscopy, CHNS elemental analysis, thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM). The adsorption of model naphthenic acid such as hexanoic acid, benzoic acid and commercial naphthenic acid from dodecane/kerosene was also investigated. The silica supported ionic liquids are good adsorbent for the removal of naphthenic acid from highly acidic model oil. The regeneration of supported ionic liquid phases as well as recovery of naphthenic acids from the supported ionic liquid phases (SILPs) was investigated.

Separation of Berberine Hydrochloride and Tetrahydropalmatine and Their Quantitative Analysis with Thin Layer Chromatography Involved with Ionic Liquids

[BMIM]OH was used in mobile and stationary phase of thin layer chromatography (TLC) to analyze berberine hydrochloride and tetrahydropalmatine for the first time. Supported imidazole ionic liquid with hydroxide ion on silica gel (SiO2·Im(+)·OH(-)) was synthesized through simple procedure and characterized by Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscope (SEM). Moreover, on the plates prepared by SiO2·Im(+)·OH(-), the contents of the above alkaloids in the Chinese patent medicine (CPM) of "Stomacheasy" capsule were successfully determined by TLC scanner. The key conditions and chromatographic behaviors were also investigated in detail. According to similar ways, ionic liquids (ILs) also can be used in other planar chromatographies in two modes. This study is expected to be helpful in expanding the application of IL and its bonded silica gel in TLC separation field.

Ionic liquids and deep eutectic mixtures: sustainable solvents for extraction processes

In recent years, ionic liquids and deep eutectic mixtures have demonstrated great potential in extraction processes relevant to several scientific and technological activities. This review focuses on the applicability of these sustainable solvents in a variety of extraction techniques, including but not limited to liquid- and solid-phase (micro) extraction, microwave-assisted extraction, ultrasound-assisted extraction and pressurized liquid extraction. Selected applications of ionic liquids and deep eutectic mixtures on analytical method development, removal of environmental pollutants, selective isolation, and recovery of target compounds, purification of fuels, and azeotrope breaking are described and discussed.

Comparison and evaluation of five types of imidazole-modified silica adsorbents for the removal of 2,4-dinitrophenol from water samples with the methyl group at different positions of imidazolium ring

The objective of this work was to improve the understanding the influence of the methyl group at different positions of imidazolium ring on the adsorption behaviors of imidazole-modified silica adsorbents. Five adsorbents named as SilprImCl, SilprM₁ImCl, SilprM₂ImCl, SilprM₄ImCl and SilprM₁M₂ImCl were synthesized using imidazole, 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 1,2-dimethylimidazole, respectively. These adsorbents were characterized by scanning electron microscope, infrared spectra, thermogravimetric analysis, elemental analysis and BET analysis. Firstly, phenol, 2-nitrophenol (2-NP), 3-nitrophenol (3-NP), 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) were used as adsorbates to investigate the selectivity of SilprImCl and its adsorption capacities followed the order of 2,4-DNP≫4-NP>2-NP≫3-NP>phenol. Therefore, 2,4-DNP was used to investigate the adsorption behaviors of the five adsorbents. It was inferred that the adsorbents are of primary anion-exchange and electrostatic nature. The electrostatic nature was affected significantly by the methyl group at different positions of imidazolium ring. The adsorbed amounts of 2,4-DNP decreased in the order of: SilprM₁M₂ImCl≈SilprM₁ImCl>SilprM4ImCl>SilprM₂ImCl>SilprImCl. The adsorption-elution experiments indicated that 2,4-DNP can be removed from aqueous solutions by a SilprM₄ImCl packed column and the recovery of 91.6% was obtained. The adsorbent could be regenerated and reused ten times at least by simple washings with HCl and water in turn.

Ion-exchange properties of imidazolium-grafted SBA-15 toward AuCl4(-) anions and their conversion into supported gold nanoparticles

Imidazolium groups were successfully prepared and grafted on the surface of SBA-15 mesoporous silica. The ion-exchange properties of the functionalized porous solid (SBA-15/R(+)Cl(-)) toward AuCl(4)(-) anions were evaluated through an ion-exchange isotherm. The calculated values of the equilibrium constant (log β = 4.47) and the effective ion-exchange capacity (t(Q) = 0.79 mmol g(-1)) indicate that the AuCl(4)(-) species can be loaded and strongly retained on the functionalized surface as counterions of the imidazolium groups. Subsequently, solids containing different amounts of AuCl(4)(-) ions were submitted to a chemical reduction process with NaBH(4), converting the anionic gold species into supported gold nanoparticles. The plasmon resonance bands, the X-ray diffraction patterns, and transmission electron microscopy images of the supported gold nanoparticles before and after thermal treatment at 973 K indicate that the metal nanostructures are highly dispersed and stabilized by the host environment.

Phosphonium-based ionic liquids in electrokinetic capillary chromatography for the separation of neutral analytes

In this work we elucidated the applicability of phosphonium-based ionic liquids (ILs) as pseudostationary phase in electrokinetic capillary chromatography (EKC) with UV-detection. The phosphonium ILs studied contain bromide, chlorine, or tosylate ions, as counter ions, and alkyl side chains of variable length on the phosphorous atom. The effects of the type and concentration of the IL, pH, ionic strength, and type of background electrolyte solution on the electroosmotic flow (EOF) and on the effective electrophoretic mobilities of some neutral model analytes were investigated and large variations in the migration times were observed. Especially the IL employed remarkably affected the strength and direction of the EOF Successful separations were obtained for neutral aromatic singly substituted analytes, namely benzene, toluene, phenol, and nitrobenzene. The results demonstrated the potential of capillary electromigration methods for rapid interaction studies between ILs and analytes, which is useful for the development of novel materials for sample preparation and separation purposes or for novel catalyst and chemical processing studies.