New stationary phase for anion-exchange chromatography

Development of novel fluor mop materials for remediation of perfluoroalkyl substances (PFAS) from groundwater

In this study we synthesized a library of 12 novel adsorbent materials that utilize a chemically well-defined silica support for superior removal of PFAS from real groundwater from a contaminated United States Air Force base. The library of sorbents probed the importance of a fluorous, hydrophobic, and electrostatic components in the removal efficacy. The materials were assessed in batch studies with PFOA, PFOS, and PFBA and compared directly to GAC and Ion Exchange resin. Adsorption kinetics with PFOS were best fit to a pseudo-second order model and equilibrium data fit well to a Langmuir isotherm model. The results were also validated externally, and the best performing material removed greater than 90% of 8 PFAS tested and was able to be regenerated up to 5 cycles. The results provide a top performing material that with further testing can be used to clean up environmentally contaminated water and provide support for the theory that a fluorous component when combined with the electrostatic and hydrophobic components, imparts both enhanced PFAS selectivity and functional resilience to the material.

Nanoconjugates based on a novel organic-inorganic hybrid silsesquioxane and gold nanoparticles as hemocompatible nanomaterials for promising biosensing applications

A new hybrid organic-inorganic silsesquioxane material, 3-n-propyl(2-amino-4-methyl)pyridium chloride (SiAMPy⁺Cl^-), was synthesized and successfully applied for the synthesis of stable nanoconjugates with gold nanoparticles (AuNPs-SiAMPy⁺). SiAMPy⁺Cl^- was obtained through a simple sol-gel procedure by using chloropropyltrimetoxysilane and tetraethylorthosilicate as precursors and 2-amino-4-methylpyridine as the functionalizing agent. The resulting material was characterized by employing FTIR, XRD, and ¹H-, ¹³C-, and ²⁹Si-NMR spectroscopy. The synthesis of AuNPs-SiAMPy⁺ nanoconjugates was optimized through a 2³ full factorial design. UV-VIS, FTIR, TEM, DLS, and ζ-potential measurements were used to characterize the nanoconjugates, which presented a spherical morphology with an average diameter of 5.8 nm. To investigate the existence of toxic effects of AuNPs-SiAMPy⁺ on blood cells, which is essential for their future biomedical applications, toxicity assays on human erythrocytes and leukocytes were performed. Interestingly, no cytotoxic effects were observed for both types of cells. The nanoconjugates were further applied in the construction of electrochemical immunosensing devices, aiming the detection of anti-Trypanosoma cruzi antibodies in serum as biomarkers of Chagas disease. The AuNPs-SiAMPy⁺ significantly enhanced the sensitivity of the biodevice, which was able to discriminate between anti-T. cruzi positive and negative serum samples. Thus, the AuNPs-SiAMPy⁺-based biosensor showed great potential to be used as a new tool to perform fast and accurate diagnosis of Chagas disease. The promising findings described herein strongly confirm the remarkable potential of SiAMPy⁺Cl^- to obtain nanomaterials, which can present notable biomedical properties and applications.

Supported Ionic Liquids Used as Chromatographic Matrices in Bioseparation-An Overview

Liquid chromatography plays a central role in biomanufacturing, and, apart from its use as a preparative purification strategy, either in biopharmaceuticals or in fine chemicals industries, it is also very useful as an analytical tool for monitoring, assessing, and characterizing diverse samples. The present review gives an overview of the progress of the chromatographic supports that have been used in the purification of high-value products (e.g., small molecules, organic compounds, proteins, and nucleic acids). Despite the diversity of currently available chromatographic matrices, the interest in innovative biomolecules emphasizes the need for novel, robust, and more efficient supports and ligands with improved selectivity. Accordingly, ionic liquids (ILs) have been investigated as novel ligands in chromatographic matrices. Given herein is an extensive review regarding the different immobilization strategies of ILs in several types of supports, namely in silica, Sepharose, and polymers. In addition to depicting their synthesis, the main application examples of these supports are also presented. The multiple interactions promoted by ILs are critically discussed concerning the improved selectivity towards target molecules. Overall, the versatility of supported ILs is here considered a critical point to their exploitation as alternatives to the more conventional liquid chromatographic matrices used in bioseparation processes.

Biocatalytic production of Ɛ-caprolactone using Geotrichum candidum cells immobilized on functionalized silica

Immobilization of the Geotrichum candidum (CCT 1205) cell with functionalized silica creates promising biocatalysts for production of ɛ-caprolactone. The results obtained by immobilization of the whole cell on SiO₂-NH₂ and SiO₂-SH supports indicate that the presence of reactive functional groups on the support may promote effective chemical bonds with the cell walls resulting the decreased dehydrogenases enzyme activity (5% yield in less than 2h) and consequently, increased Baeyer-Villiger monooxygenases enzyme activity with redacting of 25% of time reaction when is used SiO₂-NH₂ as support and 50% through use of SiO₂-SH as support relative to free cells when cyclohexanone is used as a substrate. The catalysts SiO₂-NH₂-Geotrichum candidum and SiO₂-SH-Geotrichum candidum were recycling and reused in the ɛ-caprolactone synthesis from cyclohexanone, and the biocatalysts promoted a quantitative conversion up to the eighth reaction cycle. KEY POINTS: • Immobilized microorganism is more efficient than free cell in the caprolactone synthesis. • The reaction times for amino and thiol groups in support were 3 h and 2 h, respectively. • These catalysts showed higher ɛ-caprolactone conversion at higher concentrations.

Emerging or Underestimated Silica-Based Stationary Phases in Liquid Chromatography

Several newly synthesized or forgotten silica-based stationary phases proposed for liquid chromatography are described, including non-endcapped, short-chain alkyl phases; hydrophilic and polar-endcapped stationary phases; polar-embedded alkyl phases; long-chain alkyl phases. Stationary phases with aromatic, cyanopropyl, diol and aminopropyl functionalities are also reviewed. Stationary phases of particular interest are biomolecular materials - based on immobilized cholesterol, aminoacids, peptides, proteins or lipoproteins. Packing materials involving macrocyclic chemistry (crown ethers; calixarenes; aza-macrocycles; oligo-and polysaccharides including these of marine origin - chitin- or chitosan-based; macrocyclic antibiotics) are discussed. Since many stationary phases developed for one type of applications (e.g. chiral separation) have been found useful in solving other analytical problems (e.g. drug's plasma protein binding ability), it seemed reasonable to discuss particular chemistries behind the stationary phases presented in this review rather than specific types of interactions or chromatographic modes.

N-Propyl-N'-2-pyridylurea-modified silica as mixed-mode stationary phase with moderate weak anion exchange capacity and pH-dependent surface charge reversal

Herein, we present a novel silica-based stationary phase modified with N-propyl-N'-2-pyridylurea selector. Due to the weakly basic properties of the pyridine selector and the presence of residual silanols after selector immobilization, a zwitterionic surface with a pI observed at approximately pH 5.5 was measured by electrophoretic light scattering in pH-dependent ζ-potential determinations. The capability of the new N-propyl-N'-2-pyridylurea-modified silica to serve as mixed-mode stationary phase was investigated. For this purpose, it was characterized under RP and HILIC conditions using test mixtures. Subsequent classification of this stationary phase in comparison to in-house and commercial benchmarks was carried by principal component analysis of resultant retention factors from chromatographic tests. The results show a relatively unique mixed-mode character amongst the tested stationary phases. The chromatographic retention characteristics of acidic compounds matched well the ζ-potential determinations. The application of anion-exchange at low pH values (e.g. pH 5) and ion exclusion chromatography at pH 7 for the separation of uridine 5'-mono-, di- and triphosphate demonstrated a pH-dependent umpolung of the stationary phase surface. The combination of these separation principles in a pH gradient from 5 to 7 gave rise to weak anion-exchange selectivity with a charge-inducted elution due to repulsive interactions at higher pH and resulted in a significant faster separation with improved peak shape under mild elution conditions.

Preparation of a silica stationary phase co-functionalized with Wulff-type phenylboronate and C12 for mixed-mode liquid chromatography

A silica stationary phase was designed and synthesized through the co-functionalization of silica with Wulff-type phenylboronate and C12 for mixed-mode liquid chromatography applications. The as-synthesized stationary phase was characterized by elemental analysis and Fourier Transform-InfraRed Spectroscopy (FT-IR). Retention mechanisms, including boronate affinity (BA), reversed-phase (RP) and anion-exchange (AE), were involved. Retention mechanism switching was easily realized by adjustment of the mobile phase constitution. Cis-diol compounds could be selectively captured under neutral conditions in BA mode and off-line separated in RP mode. Neutral, basic, acidic and amphiprotic compounds were chromatographed on the column in RP chromatography, while inorganic anions were chromatographed in AE chromatography to characterize the mixed-mode nature of the prepared stationary phase. In addition, the RP performance was compared with an octadecyl silica column in terms of column efficiency (N/m), asymmetry factor (A_f), retention factor (k) and resolution (Rs). The prepared stationary phase offered multiple interactions with analytes in addition to hydrophobic interactions under RP elution conditions. Based on the mixed-mode properties, off-line 2D-LC, for selective capture and separation of urinary nucleosides, was successfully realized on a single column, demonstrating its powerful application potential for complex samples.

Glycidyl alkoxysilane reactivities towards simple nucleophiles in organic media for improved molecular structure definition in hybrid materials

We report the first comprehensive study of the reactivity in organic media of (3-glycidyloxypropyl)trialkoxysilanes towards common nucleophiles. Their reactivity have to be emphasized in order to design and to improve new sol–gel hybrid synthesis.

Rapid and direct MALDI-MS identification of pathogenic bacteria from blood using ionic liquid-modified magnetic nanoparticles (Fe3O4@SiO2)

A novel method for pathogenic bacteria identification directly from blood samples using cationic ionic liquid-modified magnetic nanoparticles (CILMS) is reported.

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.

Ionic liquid-modified materials for solid-phase extraction and separation: a review

In recent years, materials science has propelled to the research forefront. Ionic liquids with unique and fascinating properties have also left their footprints to the developments of materials science during the last years. In this review we highlight some of their recent advances and provide an overview at the current status of ionic liquid-modified materials applied in solid-phase extraction, liquid and gas chromatography and capillary electrochromatography with reference to recent applications. In addition, the potential of ionic liquids in the modification of capillary inner wall in capillary electrophoresis is demonstrated. The main target material modified with ionic liquids is silica, but polymers and monoliths have recently joined the studies. Although imidazolium is still clearly the most commonly used ionic liquid for the covalently modification of materials, the exploitation of pyridinium and phosphonium will most probably increase in the future.

Research on the adsorption property of supported ionic liquids for ferulic acid, caffeic acid and salicylic acid

In this paper, the preparation of new supported ionic liquids (SILs) composed of the N-methylimidazolium cation and the quinoline cation is described. They have been confirmed and evaluated by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Six kinds of different SILs included SiO(2)·Im(+)·Cl(-), SiO(2)·Im(+)·BF(4)(-), SiO(2)·Im(+)·PF(6)(-), SiO(2)·Qu(+)·Cl(-), SiO(2)·Qu(+)·BF(4)(-) and SiO(2)·Qu(+)·PF(6)(-). The adsorption characteristics of ferulic acid (FA), caffeic acid (CA) and salicylic acid (SA) on SILs were investigated by static adsorption experiments. It was found that SiO(2)·Qu(+)·Cl(-) had excellent adsorption and desorption capacity to three tested phenolic compounds. The dynamic adsorption characteristics of FA, CA and SA on SiO(2)·Qu(+)·Cl(-) were also studied. The saturated adsorption capacity of FA, CA and SA using SiO(2)·Qu(+)·Cl(-) as adsorbent was 64.6 mg/g, 53.2 mg/g and 72.2 mg/g respectively. Using 70% ethanol as eluent, the saturated desorption efficiencies of FA, CA and SA were 97.2%, 90.3% and 96.5% respectively. Thus, SiO(2)·Qu(+)·Cl(-) had strong adsorption and separation capacity for FA, CA and SA.