Preparation of Hybrid Monolithic Columns via “One-Pot” Photoinitiated Thiol–Acrylate Polymerization for Retention-Independent Performance in Capillary Liquid Chromatography

One-pot preparation of bi-functional POSS-based hybrid monolith via photo-initiated polymerization for isolation of extracellular vesicles

Extracellular vesicles (EVs) are important participants in numerous pathophysiological processes, and could be used as valuable biomarkers to detect and monitor various diseases. However, facile EV isolation methods are the essential and preliminary issue for their downstream analysis and function investigation. In this work, a polyhedral oligomeric silsesquioxanes (POSS) based hybrid monolith combined metal affinity chromatography (MAC) and distearoyl phospholipid ethanolamine (DSPE) function was developed via photo-initiated thiol-ene polymerization. This synthesis process was facile, simple and convenient, and the obtained hybrid monolith could be applied to efficiently isolate EVs from bio-samples by taking advantages of the specific bond of Ti4+ and phosphate groups on the phospholipid membrane of EVs and the synergistic effect of DSPE insertion. Meanwhile, the eluted EVs could maintain their structural integrity and biological activity, suggesting they could be used for downstream application. Furthermore, 75 up-regulated proteins and 56 down-regulated proteins were identified by comparing the urinary EVs of colorectal cancer (CRC) patients and healthy donors, and these proteins might be used as potential biomarkers for early screening of CRC. These results demonstrated that this hybrid monolith could be used as a simple and convenient tool for isolating EVs from bio-samples and for wider applications in biomarker discovery.

Review of recent advances in development and applications of organic-silica hybrid monoliths

Organic-silica hybrid monoliths attracted attention as an alternative to extensively researched organic polymer-based and silica-based counterparts. The development and applications of these materials as extraction and separation media in capillary liquid chromatography and capillary electrochromatography were previously reviewed in several manuscripts. In this review, we will concentrate on work published since mid-2016 focusing on advances in their development using sol-gel chemistry of tetra- and trialkoxysilanes and subsequent surface modification with organic monomers, and "one-pot" strategy incorporating sol-gel chemistry of alkoxysilanes and free-radical polymerization, ring-opening polymerization, or thiol-based click polymerization with organic monomers. Approaches adapted to the preparation of hybrid monoliths made with polyhedral oligomeric silsesquioxanes will be covered as well.

Upcycling green carbon black as a reinforcing agent for styrene–butadiene rubber materials

This study reports the effects of recovered carbon black (produced in a clean and sustainable way) as a reinforcing agent on the physicochemical properties of a styrene–butadiene rubber (SBR) matrix. SBR-based composite materials are prepared with recovered green carbon black (GCB), and these are thoroughly compared to the composite materials containing conventional virgin carbon black (VCB) (produced by the incomplete combustion of petroleum products). The GCB–SBR composite materials generally show detectably inferior properties compared to the VCB–SBR composite under the same preparation conditions due to the limited functionality of the GCB filler. However, the introduction of a small amount of crosslinker, acrylate-functionalized POSS (polyhedral oligomeric silsesquioxane), into the GCB–SBR composite materials effectively enhances the overall physical properties, including the tensile strength, fracture elongation, and thermal stability. The degree of the crosslinking efficiency, thermal stability, and mechanical properties of the composite materials are optimized and thoroughly examined to demonstrate the possibility of replacing typical VCB with GCB, which can allow for upcycling the inexpensive and ecofriendly carbon black materials as effective reinforcing fillers.

Green carbon black (GCB) could be upcyclable as an eco-friendly filler for styrene butadiene rubber (SBR)-based composite materials to replace conventional virgin carbon black (VCB) upon properly utilizing POSS.

Rapid polymerization of polyhedral oligomeric siloxane-based zwitterionic sulfoalkylbetaine monolithic column in ionic liquid for hydrophilic interaction capillary electrochromatography

A novel polyhedral oligomeric siloxane (POSS)-based zwitterionic monolithic capillary column was prepared via one-pot polymerization in ionic liquid porogen, using N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine (DMMSA) and methacrylic ethyl trimethylammonium chloride (META) as binary functional monomers, and methacryl substituted POSS as cross-linker. The pore structure, permeability and homogeneity were well tuned by optimizing the polymerization conditions. The resultant monolith was characterized by scanning electron microscopy, nitrogen adsorption/desorption isotherm and Fourier transform infrared spectroscopy. The incorporation of zwitterionic ligand (DMMSA), quaternary amine group (META) and rigid POSS skeleton endows the hybrid organic-silica monolith with high hydrophilicity, electrostatic interaction and good mechanical stability, as well as a tunable electroosmotic flow over wide pH range. A close investigation of capillary electrochromatographic separations of different types of polar compounds such as bases, nucleosides and benzoic acids on such stationary phase exhibited a retention independent column efficiency up to 118,000 plates/m (thiourea), as well as a mixed-mode hydrophilic interaction chromatography (HILIC) retention mechanism including weak electrostatic interaction, hydrophobic interaction and anion exchange.

In situ photo-initiated polymerized oligonucleotide-functionalized hydrophilic capillary affinity monolith for highly selective in-tube microextraction of ochratoxin A mycotoxin

A photo-initiated polymerized oligonucleotide-grafted hydrophilic affinity monolithic column was synthesized in situ, and exploited for selective in-tube solid phase micro-extraction (IT-SPME) protocol towards the sensitive detection of ochratoxin A (OTA). Only 7 min was required for the rapid polymerization of aptamer-based affinity monolith, which was much less than the reaction time of most thermal polymerization (12-16 h) and sol-gel chemistry methods (up to 52 h). Characterizations such as polymerization recipes, structure morphology, FTIR spectrum, elemental mapping, mechanical stability, and specific recognition performance were evaluated. A significantly hydrophilic nature with a low contact angle of 15° was observed, and a mixed-mode mechanism including aptamer affinity recognition and hydrophilic interaction (HI) was employed. By coupling with HPLC-fluorescence detection, the highly specific online recognition performance was achieved with an extremely low nonspecific adsorption of the analogues. The calibration curve of OTA was obtained in the concentration range 0.05-50.00 ng·mL^-1 with a limit of detection (LOD, S/N = 3) of 0.012 ng·mL^-1. Applied to sample analysis, acceptable recovery yields of 95.1 ± 1.4% - 99.5 ± 2.2% (n = 3) were obtained in beer and red wine. The proposed method lighted a promising way to efficiently preparing a hydrophilic aptamer-affinity monolith for highly specific recognition of trace mycotoxin by IT-SPME coupled with HPLC. A hydrophilic oligonucleotide-based affinity capillary monolith was explored via in situ photopolymerization for overcoming low preparation efficiency and achieving high-performance online IT-SPME of OTA mycotoxin.

Chiral covalent organic framework-monolith as stationary phase for high-performance liquid chromatographic enantioseparation of selected amino acids

The separation of amino acid (AA) enantiomers shows significance for chemistry, food, and biology, but remains challenging due to their similar properties. A promising nanoporous chiral covalent organic framework (COF) as a stationary phase for high-performance liquid chromatography (HPLC) suffers from the irregularity and widely distributed particle size of the chiral COF. Herein, we show the facile preparation of a chiral COF-monolith as a stationary phase for HPLC enantiomeric separation of AAs via orthogonal experiments. The CTzDa-monolith is prepared by the incorporation of the model chiral COF named CTzDa into the porous poly(ethylene dimethacrylate-co-methacrylate) monolith and reveals great permeability and mechanical stability. The corresponding CTzDa-monolithic column gives better chiral HPLC separation of AAs than the commercial Poroshell 120 chiral-T column. Thermal dynamic analysis and molecular docking calculations imply the involvement of stereoscopic hydrogen, π-π, and van der Waals interactions between the CTzDa and AAs during HPLC enantioseparation. The facile incorporation of the chiral COF into the porous monolith will promote the potential of a chiral COF as a stationary phase for HPLC.

Advancements in the preparation and application of monolithic silica columns for efficient separation in liquid chromatography

Fast and efficient separation remains a big challenge in high performance liquid chromatography (HPLC). The need for higher efficiency and resolution in separation is constantly in demand. To achieve that, columns developed are rapidly moving towards having smaller particle sizes and internal diameters (i.d.). However, these parameters will lead to high back-pressure in the system and will burden the pumps of the HPLC instrument. To address this limitation, monolithic columns, especially silica-based monolithic columns have been introduced. These columns are being widely investigated for fast and efficient separation of a wide range of molecules. The present article describes the current methods developed to enhance the column efficiency of particle packed columns and how silica monolithic columns can act as an alternative in overcoming the low permeability of particle packed columns. The fundamental processes behind the fabrication of the monolith including the starting materials and the silica sol-gel process will be discussed. Different monolith derivatization and end-capping processes will be further elaborated and followed by highlights of the performance such monolithic columns in key applications in different fields with various types of matrices.

Glass Fiber-Supported Hybrid Monolithic Spin Tip for Enrichment of Phosphopeptides from Urinary Extracellular Vesicles

Extracellular vesicles (EVs) are attracting increasing interest with their intriguing role in intercellular communications. Protein phosphorylation in EVs is of great importance for understanding intercellular signaling processes. However, the study of EV phosphoproteomics is impeded by their relatively low amount in limited clinical sample volumes, and it is necessary to have a sensitive and efficient enrichment method for EV phosphopeptides. Herein, a novel Ti(IV)-functionalized and glass fiber-supported hybrid monolithic spin tip, termed PhosTip, was prepared for enriching phosphopeptides from urinary EVs. Glass fiber as the stationary phase positions the hybrid monolith in a standard pipet tip and prevents the monolith from distortion during experiments. The preparation procedure for the new PhosTip is simple and time-saving. The hybrid monolithic PhosTip provides excellent enrichment efficiency of low-abundance phosphopeptides from cell digests and urinary EVs with minimum contamination and sample loss. Using the PhosTip, we demonstrate that 5373 and 336 unique phosphopeptides were identified from 100 and 1 μg of cell lysates, while 3919 and 217 unique phosphopeptides were successfully identified from 10 and 1 mL of urinary samples, respectively. The PhosTip was finally applied to enrich phosphopeptides in urine EVs from prostate cancer patients and healthy controls and quantify 118 up-regulated proteins with phosphosites in prostate cancer samples. These results demonstrated that the PhosTip could be a simple and convenient tool for enriching phosphopeptides from clinical samples and for broader applications in biomarker discovery.

Determination of l-norvaline and l-tryptophan in dietary supplements by nano-LC using an O-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine-silica hybrid monolithic column

An analytical methodology based on an O-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD)-silica hybrid monolithic column was developed for the enantioseparation of 9-fluorenylmethoxycarbonyl (FMOC) derivatized amino acids by nano-liquid chromatography. The mobile phase was optimized including the apparent pH, content of ACN, and concentration of the buffer to obtain a satisfactory enantioresolution performance. 27 FMOC derivatized amino acids including 19 protein and 8 non-protein amino acids were tested, and 19 out of them were enantiomerically discriminated obtaining baseline separation for 11 of them. Analytical characteristics of the method were evaluated for norvaline and tryptophan in terms of linearity, precision, accuracy, limits of detection (LOD) and quantitation (LOQ) showing good performance to be applied to the enantiomeric determination of these amino acids in dietary supplements. LOD and LOQ values were 9.3 and 31 μM for norvaline enantiomers and 7.5 and 25 μM for tryptophan enantiomers, respectively. The contents of d-norvaline and d-tryptophan were below their respective LODs in all the analyzed samples. Quantitation of l-tryptophan and l-norvaline showed good agreement with the labeled contents except for one sample which did not show presence of l-norvaline, contrary to the label indication.

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A method was developed for the enantiomeric separation of amino acids by nano-LC.

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A novel quinidine-silica hybrid monolith was employed as chiral column.

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19 protein and non-protein FMOC-amino acids were enantiomerically discriminated.

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Analytical characteristics of the developed method were evaluated.

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Norvaline and tryptophan were enantiomerically determined in dietary supplements.

Integrated Microstructured Photonic Fiber as a Bifunctional Robust Frit and Efficient Electrospray Emitter of a Packed Column for Capillary Liquid Chromatography-Tandem Mass Spectrometry Analysis of Complex Biological Samples

Although capillary liquid chromatography married with tandem mass spectrometry (cLC-MS/MS) has become a powerful technique for proteomics and metabolomics research, it is still a great challenge to fabricate durable capillary-based analytical columns coupling continuous nanoflow (<1 000 nL/min) electrospray ionization (ESI) with MS, owing to the issue of clogging and fragile of emitters. Here, we proposed a simple approach to integrate microstructured photonic fibers (MPFs) into wide bore capillaries with 150 μm i.d., serving as an integral bifunctional frit or/and ESI emitter of packed columns. Two kinds of MPFs containing 126 homogeneous microchannels with different inner diameter, 3.2 μm for MPF-1 and 2.6 μm for MPF-2, were explored for preparation. The octadecylsilicate (ODS) silica-packed column using MPF-1 as a frit exhibited the lowest plate heights of 14.2-19.7 μm for five alkylbenzenes at the velocity of 1.5 mm/s, which were slightly lower than those of packed column with porous polymer monolith (PPM)-based frit by cLC coupling with ultraviolet (UV) detection. Additionally, the packed columns with integral MPF frit-emitters were further applied in analysis of a complex biological sample of digest of Hela cells by cLC-MS. An average of 7109 unique peptides could be identified in a single analysis by using MPF-1 emitter, and 7110 unique peptides were identified by using the MPF-2 emitter, which were superior to the identified result of packed column with an integral tapered tip emitter (6894 peptides). It is obvious that this novel integral MPF-based frit-emitter does not easily suffer from the issues of cracking owing to the silica cladding around independent microchannels (>100), which always encumbers both independent and integral tapered tip emitters for cLC-MS.

Fast fabrication and modification of polyoctahedral silsesquioxane-containing monolithic columns via two-step photo-initiated reactions and their application in proteome analysis of tryptic digests

A fast and robust approach was developed to fabricate and modify hybrid monolithic columns via two-step photo-initiated reactions. At first, acrylopropyl polyoctahedral silsesquioxane (acryl-POSS) and 3-(triallyl silyl) propyl acrylate (TAPA) were chosen as precursors to synthesize poly (POSS-co-TAPA) monolithic column (monolith I) via photo-initiated free-radical polymerization within 10 min, which left lots of allyl groups on the surface of monolith. Secondly, two thiol-containing compounds, penicillamine and 1-octadecanethiol (ODT), were introduced to modify the prepared poly (POSS-co-TAPA) column via photo-initiated thiol-ene click reaction within 20 min. Finally, three resulting monolithic columns were applied to separate phenolic, anilines and antibiotics mixtures. These mixtures were baseline-separated on the monolith modified with penicillamine (monolith II), exhibiting better selectivity than both pristine monolith I and that modified with ODT (monolith III). Additionally, these columns were further used for separation of tryptic digest of HeLa cells by cLC-MS/MS. The 5071 unique peptides mapped to 2442 proteins were identified from HeLa cells digest on monolith II, which were superior over those on monolith III, but slightly lower than those on monolith I. These results demonstrated that these POSS-containing columns exhibited great separation ability for complex samples.

In-situ photopolymerized polyhedral oligomeric silsesquioxane-derived monolithic capillary columns with quinidine functionality for enantioseparation by nano-liquid chromatography

The successful fabrication of monolithic capillary columns for enantiomer separations was achieved within vinylized fused silica capillaries via fast "one-pot" photo-initiated free radical polymerization reaction. A mixture consisting of polyhedral oligomeric silsesquioxane, O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydroquinidine was copolymerized in the presence of n-butanol, ethylene glycol and photo-initiator 2,2-dimethoxy-2-phenylacetophenone. The morphology of the resultant polymeric hybrid inorganic-organic material and its permeability as well as porosity can be controlled by adjusting the composition of the monomers and binary porogenic solvent. The chromatographic characteristics of the columns have been investigated. Separation factors of N-acetyl-phenylalanine (Ac-Phe) and dichlorprop dropped with decrease of chiral functional monomer. Permeability was better when the macroporogen ethyleneglycol was present at higher concentrations during the polymerization. In general, the chiral compounds were well separated (dichlorprop: α = 1.53, R_s up to 4.14; Ac-Phe: α = 1.36, R_s up to 2.69) by nano-HPLC with an optimized enantioselective monolithic capillary column which can be prepared within a few minutes.

Analysis of oligonucleotides by ion-pair reversed-phase liquid chromatography coupled with positive mode electrospray ionization mass spectrometry

Oligonucleotides are usually analyzed by ion-pair reversed-phase liquid chromatography (IP-RPLC) coupled with negative mode electrospray ionization mass spectrometry (ESI-MS) due to their highly negative charged phosphodiester backbones. Herein, the signal suppression effect of triethylamine (TEA) adducts caused the ion-pair reagent TEA/hexafluoroisopropanol (HFIP) is greatly alleviated after improving the in-source energy in positive mode ESI-MS. This strategy is applied for different RNA sequencing through analyzing their formic acid hydrolysates via IP-RPLC MS. Comparing with negative ion mode, we demonstrate that IP-RPLC MS analysis in positive ion mode is more suitable for RNA sequencing with fewer contaminant interferences. Finally, simultaneous online separation and detection of oligonucleotides and protein digests are achieved in positive ion mode IP-RPLC MS analysis with little interference to each other.

Thiol-ene polymerization for hierarchically porous hybrid materials by adding degradable polycaprolactone for adsorption of bisphenol A

Hierarchically porous materials with multiple pore structures have the potential application in catalysis, separation or bioengineering. A concept was introduced to design and fabricate hierarchically porous hybrid materials (HPHMs) simultaneously containing mesopores and macropores. The proof-of-concept design was demonstrated by fabrication of several kinds of hybrid materials by adding degradable polycaprolactone (PCL) additive, which was simple and easy-operating. The specific surface areas of HPHMs prepared with polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and 1,4-dithiothreitol (DTT) could reach 727 m²/g by adding 25% PCL additive, while the HPHMs were imperforate prior to degradation of PCL. The characterization further indicated that the macropores could be controlled by the amount of PCL additive. Moreover, the porous properties of HPHMs were influenced by the molecular weight of PCL. Other dithiols compounds were also successful in preparing HPHMs with high specific surface areas over 400 m²/g. Due to hydrophobic interaction and hydrogen bond interaction, the HPHM exhibited good adsorption ability for bisphenol A (BPA) in aqueous solution. Adsorption equilibrium could be achieved within 30 min, and the adsorption capacity was up to 157.4 mg/g. Meanwhile, the removal efficiency was found to be 95.37% for BPA.

One-step fabrication of cinchona-based hybrid monolithic chiral stationary phases via photo-initiated thiol-ene polymerization for cLC enantioseparation

Although various click polymerization reactions (thiol-ene, thiol-yne, thiol-Michael, thiol-epoxy and amine-epoxy) have been utilized to prepare either hybrid or organic monolithic columns with homogeneous network structures, there were few reports on fabrication of monolithic CSPs via click polymerization. Herein, a fast and robust approach was explored to fabricate cinchona-based monolithic hybrid CSPs via photo-initiated thiol-ene polymerization within 10 min in one step. A self-synthesized octakis(3-mercaptopropyl) octasilsesquioxane (POSS-SH) was polymerized with phenylisocyanate cinchonidine (PCD) and (+)-N,N'-diallyl-L-tartardiamide (DATDA) or 1,2,4-trivinylcyclohexane (TVCH). The resulting two kinds of as-synthesized monolithic CSPs, poly(POSS-co-DATDA-co-PCD) and poly(POSS-co-TVCH-co-PCD), were evaluated for cLC enantioseparation of acidic racemates. It was found that they exhibited different enantioseparation ability due to using different multivinyl crosslinkers. The influence of ACN content in mobile phase on the enantioseparation of acidic racemates was investigated. The separation mechanism was also discussed on the basis of a comparison of enantioseparation on two kinds of hybrid monolithic CSPs.

Thiol-radical-mediated polymerization for preparation of POSS-containing polyacrylate monoliths in capillary liquid chromatography

Through introducing octakis (3-mercaptopropyl) octasilsesquioxane (POSS-SH) synthesized in our lab to the prepolymerization solution containing stearyl acrylate (SA), 1,6-hexanediol ethoxylate diacrylate (HEDA) in the existence of porogenic solvents (tetrahydrofuran, 1,4-butanediol and 1-propanol), a POSS-containing hybrid monolithic column was fabricated via photo-initiated thiol-acrylate polymerization within 7 min. The resulting poly(SA-co-HEDA-co-POSS) monoliths were investigated by physical characterization and chromatographic evaluation. It was found that both the additive amount of thiol group and the proportion of porogenic solvents played vital effect on column efficiency, pore morphology and hydrophobicity of monolithic columns. Consequently, the poly(SA-co-HEDA-co-POSS) monolith possessed superior thermal stability, suitable permeability and homogeneous microstructure. The highest column efficiency was ∼111,000 N m^-1 for butylbenzene at the linear velocity of 0.71 mm s^-1 in reversed-phase liquid chromatography. Subsequently, baseline separations of 9 phenolic compounds, 5 anilines and 5 antibiotics were achieved, indicating the monolithic poly(SA-co-HEDA-co-POSS) column had great ability for separation of small molecules. The analytic results of the tryptic digest of BSA and HeLa were also proved that the hybrid monolith had potential for the analysis of complicated biological samples.

Fast preparation of hybrid monolithic columns via photo-initiated thiol-yne polymerization for capillary liquid chromatography

Although several approaches have been developed to fabricate hybrid monoliths, it would still take a few hours to finish the formation of monoliths. Herein, photo-initiated thiol-yne polymerization was first adopted to in situ fabricate hybrid monoliths within the confines of UV-transparent fused-silica capillary. A silicon-containing diyne (1,3-diethynyltetramethyl-disiloxane, DYDS) was copolymerized with three multithiols, 1,6-hexanedithiol, trimethylolpropane tris(3-mercaptopropionate) and pentaerythriol tetrakis(3-mercaptopropionate), by using a binary porogenic system of diethylene glycol diethyl ether (DEGDE)/poly(ethylene glycol) (PEG200) within 10 min. Several characterizations of three hybrid monoliths (assigned as I, II and III, respectively) were performed. The results showed that these hybrid monoliths possessed bicontinuous porous structure, which was remarkably different from that via typical free-radical polymerization. The highest column efficiency of 76,000 plates per meter for butylbenzene was obtained on the column I in reversed-phase liquid chromatography (RPLC). It was observed that the efficiencies for strong-retained butylbenzene were almost close to those of weak-retained benzene, indicating a retention-independent efficient performance of small molecules on hybrid column I. The surface area of this hybrid monolith was very small in the dry state (less than 10.0 m²/g), and the chromatographic behavior of hybrid monolithic columns would be possibly explained by radical-mediated step-growth process of thiol-yne polymerization. Finally, the column I was applied for separation of BSA tryptic digest by cLC-MS/MS, indicating satisfactory separation ability for complicated samples.

Layer-by-layer preparation of 3D covalent organic framework/silica composites for chromatographic separation of position isomers

A layer-by-layer approach was developed to fabricate COF-300@SiO₂ for HPLC separation of position isomers.

Preparation of a long-alkyl-chain-based hybrid monolithic column with mixed-mode interactions using a "one-pot" process for pressurized capillary electrochromatography

A simple "one-pot" approach for the preparation of a new vinyl-functionalized organic-inorganic hybrid monolithic column is described. In this improved method, the hydrolyzed alkoxysilanes of tetramethoxysilane and triethoxyvinylsilane were used as precursors for the synthesis of a silica-based monolith, while 1-hexadecene and sodium ethylenesulfonate were used as vinyl functional monomers along with azobisisobutyronitrile as an initiator. The effects of reaction temperature, urea content, and composition of organic monomers on the column properties (e.g. morphology, mechanical stability, and chromatographic performance) were investigated. The monolithic column was used for the separation of neutral solutes by reversed-phase pressurized capillary. Furthermore, the monolith can separate various aromatic amines, which indicated its excellent cation-exchange capability and hydrophobic interactions. The baseline separation of the aromatic amines was obtained with a column efficiency of up to 78 000 plates/m.

Facile preparation of multi-functionalized hybrid monoliths via two-step photo-initiated reactions for two-dimensional liquid chromatography-mass spectrometry

A facile approach was developed to prepare hybrid monoliths with different functions via two-step photo-initiated reactions. Firstly, acrylopropyl polyhedral oligomertic silsesquioxane (acryl-POSS) and propargyl acrylate (PA) were used as precursors to synthesize alkynyl-functionalized hybrid monoliths via photo-initiated free radical polymerization. Secondly, the hybrid monoliths were modified with 1-octadecanethiol (ODT) and sodium 3-mercapto-1-propanesulfonate (SMPS) via photo-initiated thiol-yne click reaction to prepare reversed-phase (RP) and strong cation-exchange (SCX) hybrid monoliths, respectively. The results of chromatographic characterization indicated that the column efficiencies for alkylbenzenes on ODT-modified hybrid monolith reached 84,000-87,700 plates per meter at the velocity of 0.58mm/s, and also revealed a retention-independent efficient performance of small molecules in isocratic elution. The SMPS-modified hybrid monolith exhibited both hydrophobicity and ion-exchange mechanisms, and the dynamic binding capacity was calculated to be 1.4×10^-4μmol/cm. Human Hela cells tryptic digest was well separated on ODT-modified hybrid monolith in one-dimensional RPLC-MS/MS, and 2786 unique peptides and 685 proteins were identified. Furthermore, the SMPS-modified monolith coupled with ODT-modified monolith was used for two-dimensional separation of human Hela cells tryptic digest in SCX-RPLC-MS/MS, and the results showed that 9744 unique peptides and 2749 proteins were identified. Compared to those identified in one-dimensional RP system, the total numbers of unique peptides and proteins identified in SCX-RP system increased by 249.7% and 301.3%, respectively.

Enhancing the Mass Spectrometry Sensitivity for Oligonucleotide Detection by Organic Vapor Assisted Electrospray

There are two challenges in oligonucleotide detection by liquid chromatography coupled with mass spectrometry (LC-MS), the serious ion suppression effects caused by ion-pair reagents and the low detection sensitivity in positive mode MS. In this study, highly concentrated alcohol vapors were introduced into an enclosed electrospray ionization chamber, and oligonucleotides could be well detected in negative mode MS even with 100 mM triethylammonium acetate (TEAA) as an ion-pair reagent. The MS signal intensity was improved 600-fold (for standard oligonucleotide dT15) by the isopropanol vapor assisted electrospray, and effective ion-pair LC separation was feasibly coupled with high-sensitive MS detection. Then, oligonucleotides were successfully detected in positive mode MS with few adducts by propanoic acid vapor assisted electrospray. The signal intensity was enhanced more than 10-fold on average compared with adding acids into the electrospray solution. Finally, oligonucleotides and peptides or histones were simultaneously detected in MS with little interference with each other. Our strategy provides a useful alternative for investigating the biological functions of oligonucleotides.

One pot synthesis of carboxyl functionalized-polyhedral oligomeric siloxane based monolith via photoinitiated thiol-methacrylate polymerization for nano-hydrophilic interaction chromatography

A hybrid monolith exhibiting almost retention independent separation performance in hydrophilic interaction chromatography (HILIC) was obtained by one-pot photoinitiated thiol-methacrylate polymerization. Polyhedral oligomeric silsesquioxane containing methacrylate units (POSS-MA) was used as the main monomer and crosslinking agent, together with a hydrophilic ligand with two carboxyl groups, mercaptosuccinic acid (MSA) as the thiol agent and chromatographic ligand. The isocratic separation of nucleosides, nucleotides and organic acids on MSA attached-poly(POSS-MA) monolith was investigated in HILIC mode. The van-Deemter plots for obtained for nucleosides, nucleotides and benzoic acids clearly showed that there were two regions in each graph with two different slopes in the studied range of linear flow rate (i.e. 0.2-4.3mm/s). The slope of plate height-linear velocity curve was so small in the low linear velocity region between 0.2-2.1mm/s while the slope in high linear velocity region between 2.1-4.3mm/s was so higher with respect to the first region. The van-Deemter plots sketched for all analyte grous used in HILIC mode obeyed this tendency Almost "retention independent plate height behavior" was demonstrated in HILIC, using nucleotides, nucleotides or benzoic acids as the analytes in the linear velocity range of 0.2-2.1mm/s. This behavior was explained by the porous structure of the synthesized monolith facilitating the convective transport of analytes. The variation of plate height was not retention-independent within high linear velocity range (>3.2mm/s) when nucleosides were separated in HILIC mode.

Facile Preparation of Titanium(IV)-Immobilized Hierarchically Porous Hybrid Monoliths

Hierarchically porous materials have become a key feature of biological materials and have been widely applied for adsorption or catalysis. Herein, we presented a new approach to directly prepare a phosphate-functionalized hierarchically porous hybrid monolith (HPHM), which simultaneously contained mesopores and macropores. The design was based on the copolymerization of polyhedral oligomeric vinylsilsesquioxanes (vinylPOSS) and vinylphosphonic acid (VPA) by adding degradable polycaprolactone (PCL) additive. The phosphate groups could be directly introduced into the hybrid monoliths. This approach was simple and time-saving, and overcame the defect of a rigorous, complex process for preparing traditional Ti⁴⁺-immobilized metal ion affinity chromatography (IMAC) materials. The specific surface area of an optimal hybrid monolith could reach 502 m²/g obtained by nitrogen adsorption/desorption measurements, which originated from the degradation of PCL. Meanwhile, the characterization of scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) also suggested that the macropores existed in the hybrid monoliths. The size of macropores could be controlled by the content of PCL in the polymerization mixture. The prepared Ti⁴⁺-IMAC HPHMs exhibited high adsorption capacity (63.6 mg/g for pyridocal 5'-phosphatemonohydrate), and excellent enrichment specificity (tryptic digest of β-casein/BSA at a molar ratio of 1:1000) and sensitivity (tryptic digest of 5 fmol of β-casein). Moreover, the Ti⁴⁺-IMAC HPHMs provided effective enrichment ability of low-abundance phosphopeptides from human serum and HeLa cell digests.

Polymer monolith containing an embedded covalent organic framework for the effective enrichment of benzophenones

A COF modified poly(glycidyl methacrylate–ethylene dimethacrylate) monolith was prepared and used for the microextraction of benzophenones in urine and serum samples.

Sulfur and Its Role In Modern Materials Science

Although well-known and studied for centuries, sulfur continues to be at the center of an extensive array of scientific research topics. As one of the most abundant elements in the Universe, a major by-product of oil refinery processes, and as a common reaction site within biological systems, research involving sulfur is both broad in scope and incredibly important to our daily lives. Indeed, there has been renewed interest in sulfur-based reactions in just the past ten years. Sulfur research spans the spectrum of topics within the physical sciences including research on improving energy efficiency, environmentally friendly uses for oil refinery waste products, development of polymers with unique optical and mechanical properties, and materials produced for biological applications. This Review focuses on some of the latest exciting ways in which sulfur and sulfur-based reactions are being utilized to produce materials for application in energy, environmental, and other practical areas.