Monolithic stationary phases with incorporated fumed silica nanoparticles. Part I. Polymethacrylate-based monolithic column with incorporated bare fumed silica nanoparticles for hydrophilic interaction liquid chromatography

Hydrophobic AEROSIL®R972 Fumed Silica Nanoparticles Incorporated Monolithic Nano-Columns for Small Molecule and Protein Separation by Nano-Liquid Chromatography

A new feature of hydrophobic fumed silica nanoparticles (HFSNPs) when they apply to the preparation of monolithic nano-columns using narrow monolithic fused silica capillary columns (e.g., 50-µm inner diameter) was presented. The monolithic nano-columns were synthesized by an in-situ polymerization using butyl methacrylate (BMA) and ethylene dimethacrylate (EDMA) at various concentrations of AEROSIL^®R972, called HFSNPs. Dimethyl formamide (DMF) and water were used as the porogenic solvents. These columns (referred to as HFSNP monoliths) were successfully characterized by using scanning electron microscopy (SEM) and reversed-phase nano-LC using alkylbenzenes and polyaromatic hydrocarbons as solute probes. The reproducibility values based on run-to-run, column-to-column and batch-to-batch were found as 2.3%, 2.48% and 2.99% (n = 3), respectively. The optimized column also indicated promising hydrophobic interactions under reversed-phase conditions, while the feasibility of the column allowed high efficiency and high throughput nano-LC separations. The potential of the final HFSNP monolith in relation to intact protein separation was successfully demonstrated using six intact proteins, including ribonuclease A, cytochrome C, carbonic anhydrase isozyme II, lysozyme, myoglobin, and α-chymotrypsinogen A in nano-LC. The results showed that HFSNP-based monolithic nanocolumns are promising materials and are powerful tools for sensitive separations.

Nano-liquid chromatography with a new nano-structured monolithic nanocolumn for proteomics analysis

Herein, we report the preparation and application of a new nano-structured monolithic nanocolumn based on modified graphene oxide using narrow fused silica capillary column (e.g., 50 μm internal diameter). The nanocolumn was prepared by an in situ polymerization using butyl methacrylate, ethylene dimethacrylate, and methacryloyl graphene oxide nanoparticles. Dimethyl formamide and water were used as the porogenic solvent. After polymerization, the obtained nanocolumn was coated with dimethyloctadecylchlorosilane in order to enhance the hydrophobicity. Both isocratic and gradient nano-liquid chromatographic separations for small molecules (e.g., alkylbenzenes) and macromolecules (e.g., intact proteins) were performed. Theoretical plates number up to 3600 plates/m in isocratic mode for propylbenzene were achieved. It was demonstrated that the feasibility of graphene oxide modified monolithic nanocolumn for high-efficiency and high-throughput nanoscale proteomics analysis. The high resolving power of monolithic nanocolumn yielded sensitive protein separation with narrower peak width while a high-resolution analysis of peptides from trypsin-digested cytochrome C could be obtained. Graphene oxide based monolithic nanocolumns are promising and can allow to powerful tools for trace proteom sample analysis.

Graphene oxide-octadecylsilane incorporated monolithic nano-columns with 50 μm id and 100 μm id for small molecule and protein separation by nano-liquid chromatography

In this study, graphene oxide-octadecylsilane incorporated monolithic nano-columns were developed for protein analysis by nano liquid chromatography (nano LC). The monolithic column with 100 μm id was first prepared by an in situ polymerization using ethylene dimethacrylate (EDMA), 3-chloro-2-hydroxypropylmethacrylate (HPMA-Cl), and methacryloyl graphene oxide nanoparticles (MGONPs). MGONPs were synthesized by the treatment of 3-(trimethoxysilyl)propylmethacrylate (TMSPM) and GO. Tetrahydrofuran (THF) and dodecanol were used as the porogenic solvent. The resulting column was functionalized by dimethyloctadecylch lorosilane (DODCS) for the enhancement of hydrophobicity. The functionalization greatly improved the baseline separation of hydrophobic compounds such as polyaromatic hydrocarbons (PAHs). The optimized monolith with respect to total polymerization mixture was characterized by using Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) X-ray diffraction (XRD) and chromatographic analyses. The blank monoliths without functionalization exhibited poor separation while a good separation performance of MGONPs functionalized monoliths was achieved. The monolith with 100 μm id was evaluated in protein separation in nano LC using RNase A, Cytochrome C, Lysozyme, Trypsin, and Ca isozyme II as the test proteins. It was shown that protein separation mechanism was based on large π-system of GO and hydrophobicity of the monolithic structure. Theoretical plates number up to 57 600 plates were achieved. The nano-column with 50 μm id was also prepared using the same polymerization mixture under the same chemical conditions. These nano-columns were employed for protein separation by nano LC, and the dependence of both nano-column performance on the internal diameter was also discussed.

Effect of Fumed Silica Nanoparticles on Ultraviolet Aging Resistance of Bitumen

In this study, bitumen modified by fumed silica nanoparticles was characterized through dynamic shear rheometer tests, scanning electron microscopy, and Fourier transform infrared spectroscopy. The fumed silica nanoparticles were used in three different ratios, i.e., 0.1, 0.2 and 0.3 wt.-% of bitumen. Specifically, the modified bitumen characteristics were studied after laboratory aging by analyzing the chemical composition and rheological properties. From the determination of oxidation degree and carbonyl index it was found that the resistance of the modified bitumen to ultraviolet aging was improved with the increasing nanoparticle content. In bitumen modified by fumed silica nanoparticles, the nanoparticles were well dispersed. Moreover, the results illustrated that the bitumen properties were improved, and the improvement effect of 0.1 wt.-% fumed silica nanoparticles was more distinct than the higher concentrations.

Organic polymer monolithic columns with incorporated bare and cyano-modified fumed silica nanoparticles for use in hydrophilic interaction liquid chromatography

This research article presents the preparation and characterization of monolithic columns with incorporated bare fumed silica nanoparticles (FSNPs) and cyano-modified FNSPs (CN-FSNPs) and their subsequent use in hydrophilic interaction liquid chromatography (HILIC) of neutral, polar, and low molecular weight solutes. The monolithic support was based on the in situ polymerization of glyceryl monomethacrylate (GMM) and ethylene glycol dimethacrylate (EDMA) yielding the poly(GMM-co-EDMA) monolith for the incorporation of bare FNSPs and of CN-FSNPs. The poly(GMM-co-EDMA) functioned as a “true support” for bare FSNPs and CN-FSNPs “stationary phases” as manifested by bare FSNPs and CN-FSNPs being the major contributors to solute retention and column selectivity. Overall, the prepared bare FSNPs and CN-FSNPs stationary phases proved useful in HILIC of small polar solutes including dimethylformamide, formamide, thiourea, nucleobases, nucleosides, organic acids, food additives, vitamins, and biological amines.

An organic polymer monolith modified with an amino acid ionic liquid and graphene oxide for use in capillary electrochromatography: application to the separation of amino acids, β-blockers, and nucleotides

The preparation of an organic polymer monolithic column modified with an amino acid ionic liquid and graphene oxide (AAIL-GO) and its application to capillary electrochromatography (CEC) was described. The AAIL tetramethylammonium-L-arginine was bonded to a monolithic column that was previously modified with graphene oxide by using an hydrochloride/N-hydroxysuccinimide coupling reaction. The morphology of a poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith was examined by scanning electron microscopy. The incorporation of AAIL and graphene oxide was detected by infrared spectroscopy and elemental analysis. The resulting monolithic column produced a strong and stable electroosmotic flow from the anode to the cathode in the pH range from 3 to 9. Compared with a column modified with AAIL or graphene oxide only, the AAIL-GO-modified column has a better separation ability for amino acids, β-blockers, and nucleotides (the resolution of three amino acids: 2.231 and 2.036, β-blockers: 2.779 and 2.470 and nucleotides: 8.345 and 3.321). Molecular modeling was applied to demonstrate the separation mechanism of small molecules which showed a good support for experimental results. Graphical abstract Schematic representation of capillary electrochromatography (CEC) systems with an amino acid ionic liquid-graphene oxide modified organic polymer monolithic column as stationary phases for separation of amino acids, β-blockers, and nucleotides.

Covalent organic framework incorporated chiral polymer monoliths for capillary electrochromatography

A covalent organic framework, Schiff base network-1 (SNW-1), was synthesized and incorporated into cellulase based poly(glycidyl methacrylate-co-ethylene dimethacrylate) (cellulase@poly(GMA-EDMA-SNW-1)) monolith to afford a novel chiral stationary phase for capillary electrochromatography (CEC). SNW-1 is attractive as a stationary phase for CEC because it not only features high surface areas but also provides conjugate structures and abundant amine groups to give π-π electrostatic stacking and hydrogen bonding property. Incorporation of SNW-1 into monolithic column could improve the column efficiency and increase the interactions between the tested racemates and the stationary phase thus significantly improved their CEC separation. The obtained monoliths were characterized by scanning electron microscopy, elemental analysis and nitrogen adsorption. Moreover, effects of SNW-1 concentration, immobilization pH of cellulase and CEC conditions were also investigated. Under the optimized conditions, the cellulase@poly(GMA-EDMA-SNW-1) monolith exhibited excellent enantioseparation performance for eight pairs of different classes of chiral drugs including β-blockers, antihistamines and anticoagulants. Satisfactory repeatability was achieved with relative standard deviations for intra-day, inter-day and column-to-column runs less than 4.5%, and batch-to-batch runs less than 6.8%. The experiment results reveal that the combination of the versatile features of monoliths and unique properties of SNW-1 could be a promising strategy for chiral separation.

An insight into chiral monolithic stationary phases for enantioselective high-performance liquid chromatography applications

In this review, three main classes of chiral monolithic stationary phases, namely silica-, organic polymer-, and hybrid-based monolithic stationary phases, are covered. Their preparations, applications, and advantages compared with the conventional-packed and open-tubular capillary columns are discussed. A detailed description of the different types and techniques used for the introduction of chiral selectors into the monolithic matrices such as immobilization, functionalization, coating, encapsulation, and bonding. Special emphasis is given to the recent developments of chiral selectors in HPLC monolithic stationary phases during the past 18 years.

Organic polymer-based monolithic stationary phases with incorporated nanostructured materials for HPLC and CEC

This review article is concerned with the recent advances made in the field of organic polymer-based monoliths with incorporated nanostructured materials (NSMs) for use in liquid chromatography and capillary electrochromatography. It covers the pertinent literature published over the last 7-8 years with a total of 56 references. The present article has two distinct parts: one major part encompassing "traditional" organic polymer-based monoliths modified with NSMs and a minor part on cryogels modified with NSMs.