Hydrophilic Monolith Research Articles

NIR‐emitting Electrochromic Windows for Cold Climate Region Buildings

AbstractElectrochromic devices (ECDs) comprising visible/near‐infrared (NIR) transparent amorphous indium zinc oxide (a‐IZO) outermost layers and novel NIR‐emitting electrolytes are proposed for smart windows of buildings in cold climate regions. The electrolytes are composed of a di‐urethane cross‐linked poly(oxyethylene)(POE)/siloxane hybrid matrix (d‐Ut(600), 600 is the average molecular weight of the POE chains in gmol−1), 1‐butyl‐3‐methylimidazolium chloride ionic liquid, and the Er(tta)3(H2O)2 complex (tta− is 2‐thenoyltrifluoracetonate). The electrolytes, synthesized by sol‐gel route, were obtained as transparent, flexible, and hydrophilic monoliths with nanoscale surface roughness, exhibiting emission in the NIR wavelength region. The first electro‐optical tests, performed in 2019, with an archetypal ECD including amorphous tungsten oxide and crystalline nickel oxide as EC layers, a‐IZO as outermost layers, and d‐Ut(600)400Er(tta)3(H2O)2[Bmim]Cl (400 is the molar ratio of oxyethylene units/Er3+ ion) as the electrolyte, demonstrated rather low coloration efficiency (CEin/CEout) values of −4/+6 cm2 C−1 at 555 nm. After 3 years of storage at rest in the dark and at room temperature, the same device demonstrates a huge performance enhancement, leading to CEin/CEout values about two orders of magnitude higher, apart from higher optical density, and improved cycling stability. In addition, this device offers a bright hot, and semi‐bright warm dual modulation operation suitable for smart windows of skylights, roof lights, upper windows, inclined glazing, and privacy glazing of buildings located in cold climate regions.

A comprehensive evaluation of a polymeric zwitterionic hydrophilic monolith for nucleotide separation.

Rapid and effective separation of nucleotides (NTs) and their derivatives is crucial for studying their physiological functions. In this work, we comprehensively evaluated the separation ability of a zwitterionic hydrophilic monolith, i.e., poly(N,N-dimethyl-N-(3-methacrylamidopropyl)-N-(3-sulfopropyl)ammonium betaine-co-N,N'-methylenebisacrylamide) (poly(SPP-co-MBA)) for NTs analysis, including its selectivity, chemical stability under extremely basic condition and compatibility with hydrophilic interaction liquid chromatography (HILIC) coupled with mass spectrometry (HILIC-MS). The poly(SPP-co-MBA) monolith exhibited excellent chemical stability, as evidenced by the low relative standard deviation of retention time (0.16-1.05%) after 4000 consecutive injections over one month under strong alkaline elution condition (pH 10). After optimizing the separation conditions, including buffer pH and concentration, organic solvent content and column temperature, four nucleoside triphosphates, five nucleoside diphosphates and five nucleoside monophosphates were baseline separated within 7min. Additionally, the mixtures containing one nucleoside and its corresponding mono-, di-, and triphosphates were baseline separated within only 3min, respectively. It is good HILIC-MS compatibility was also confirmed by the satisfactory peak shape and high response of nine NTs. Overall, the proposed poly(SPP-co-MBA) monolith exhibited good mechanical stability and compatibility of HILIC-MS, making it a promising technique for NTs analysis.

Preparation of miniaturized hydrophilic affinity monoliths: Towards a reduction of non-specific interactions and an increased target protein density

In affinity chromatography, non-specific interactions between the ligands and the affinity column may affect the results, leading to misinterpretations during the investigation of protein-ligand interactions (detection of false positives in ligand screening, lack of specificity in purification). Such non-specific interactions may arise both from the underlying support or from the target protein itself. If the second ones are protein-dependent (and cannot be studied in a general framework), the first ones occur in the same way regardless of the immobilized target. We propose a methodology to identify the origin of such non-specific interactions with the underlying material of the affinity column. This methodology relies on the systematic investigation of the retention behavior of a set of 41 low-molecular weight compounds covering a wide chemical space (net charge, log D, functionality). We first demonstrate that the main source of non-specific interactions on the most commonly used GMA-co-EDMA monolith comes from hydrophobic effects. To reduce such non-specific interactions, we developed a new hydrophilic glycidyl methacrylate-based monolith by replacing the EDMA crosslinker by the more hydrophilic NN’ Methylenebisacrylamide (MBA). Optimization of the synthesis parameters (monomer content, initiation type, temperature) has focused on the reduction of non-specific interaction with the monolithic support while maximizing the amount of protein that can be grafted onto the monolith at the issue of its synthesis. The retention data of the 41 test solutes on the new poly(GMA-co-MBA) monolith shows a drastic reduction of non-specific interactions except for cationic compounds. The particular behavior of cationic compounds is due to their electrostatic interactions with carboxylic groups resulting from the partial acidic hydrolysis of amide groups of MBA during the epoxide ring opening step. So, the ring opening step in acidic media was replaced by a hot water treatment to avoid side reaction on MBA. The new monolith poly(GMA-co-MBA) not only has improved hydrophilic surface properties but also a higher protein density (16 ± 0.8 pmol cm−1 instead of 8 ± 0.3 pmol cm−1). To highlight the benefits of this new hydrophilic monolith for affinity chromatographic studies, frontal affinity chromatography experiments were conducted on these monoliths grafted with con A.

Hydrophilic carbon monoliths derived from metal-organic frameworks@resorcinol-formaldehyde resin for atmospheric water harvesting

Hydrophilic carbon monoliths derived from metal-organic frameworks@resorcinol-formaldehyde resin for atmospheric water harvesting

Simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC using a highly hydrophilic monolith

Urea and allantoin are two important additives in cosmetic products for the treatment of dry skin as well as for skin protection and regeneration. In this research, a highly hydrophilic monolith prepared by co-polymerization of N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and N,N’-methylenebisacrylamide (MBA) was first exploited for the simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC in the HILIC mode. The whole separation process could be completed within six minutes using isocratic elution. Due to the extremely high hydrophilicity of this monolithic column, a relatively low content (80%) of ACN in the mobile phase was required to achieve satisfactory separation, and therefore the solubility problems for polar compounds was also avoided in comparison with previously reported results on the commercial columns. Method validation was also accomplished with respect to linearity, reproducibility, selectivity, recovery, stability, LOD and LOQ. The recoveries of urea and allantoin from spiked cosmetic samples were 95.6%-100% and 94.1%-99.9%, respectively. Validation results indicate that this HILIC method based on the miniaturized poly(SPDA-co-MBA) monolith can be applied successfully to the fast and efficient determination of urea and allantoin in cosmetic samples. The miniaturized column format, the low sample consumption (20 nL), and excellent separation efficiency could make this highly hydrophilic monolith an attractive choice for the detection of trace polar analytes from complex samples in future.

Polyvinyl alcohol-based hydrophilic monoliths from water-in-oil high internal phase emulsion template

Herein, we report a new approach to fabricate polyvinyl alcohol (PVA) based hydrophilic monoliths by alcoholysis of porous emulsion-templated polyvinyl acetate (PVAc). The precursory PVAc-based monolith is obtained by polymerization of a W/O high internal phase emulsion (HIPE) containing vinyl acetate as the external phase while water as the internal phase. As an alcoholysis-stable tri-functional commonomer, triallyl isocyanurate is chosen as the crosslinking agent to prevent possible collapse of the polymeric skeleton and the consequent losses in mechanical properties during the alcoholysis step. By alcoholysis of the resulting PVAc-based monolith, the PVA-based monoliths are successful prepared as confirmed by FTIR analysis. BET analysis and SEM observation confirm the formation of open-cell and highly interconnected porous structures of PVA-based monoliths with surface areas of around 16m2/g. Stemming from the intrinsic hydrophilicity of hydroxyl and morphology, PVA-based monoliths exhibit great enhancement in hydrophilicity with a much lower water contact angles than that of PVAc-based monoliths.

The effect of charged groups on hydrophilic monolithic stationary phases on their chromatographic properties

In order to investigate the effect of charged groups present in hydrophilic monolithic stationary phases on their chromatographic properties, three charged hydrophilic monomers, i.e. N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA), [2-(acryloyloxy)ethyl]trimethylammonium chloride (AETA), and 3-sulfopropyl acrylate potassium salt (SPA) were co-polymerized with the crosslinker N,N'-methylenebisacrylamide (MBA), respectively. The physicochemical properties of the three resulting charged hydrophilic monolithic columns were evaluated using scanning electron microscopy, ζ-potential analysis and micro-HPLC. High column efficiency was obtained on the three monolithic columns at a linear velocity of 1mm/s using thiourea as test compound. Comparative characterization of the three charged HILIC phases was then carried out using a set of model compounds, including nucleobases, nucleosides, benzoic acid derivatives, phenols, β-blockers and small peptides. Depending on the combination of stationary phase/mobile phase/solute, both hydrophilic interaction and other potential secondary interactions, including electrostatic interaction, hydrogen-bonding interaction, molecular shape selectivity, could contribute to the over-all retention of the analytes. Because of the strong electrostatic interaction provided by the quaternary ammonium groups in the poly (AETA-co-MBA) monolith, this cationic HILIC monolith exhibited the strongest retention for benzoic acid derivatives and small peptides with distorted peak shapes and the weakest retention for basic β-blockers. The sulfonyl groups on the poly (SPA-co-MBA) hydrophilic monolith could provide strong electrostatic attraction and hydrogen bonding for positively charged analytes and hydrogen-donor/acceptor containing analytes, respectively. Therefore, basic drugs, nucleobases and nucleotides exhibited the strongest retention on this anionic monolith. Because of the weak but distinct cation exchange properties of the zwitterionic poly (SPDA-co-MBA) hydrophilic monolith, it exhibited the best separation for most test analytes (including phenols, β-blockers and small peptides) in terms of selectivity, peak shape and analysis time. The poly (AETA-co-MBA) hydrophilic monolithic column provides the best separation of nucleobases and nucleosides. These results could guide the selection and application of these charged HILIC monoliths in the future.

Preparation of an improved hydrophilic monolith to make trypsin-immobilized microreactors.

In the present work the preparation of capillary-based microreactors with immobilized trypsin was investigated. The monolithic support was synthesized from 2-hydroxyethyl methacrylate (HEMA) as a functional monomer and N,N'-methylenebis(acrylamide) (MBA) as a hydrophilic crosslinker. Two monomers contents in the polymerization mixture (27% and 35%) at the ratio of HEMA:MBA=3:2 were tested. The results indicated that the heated mixture of the above monomers and the porogen consisting of 40% 1-decanol, 40% 2-propanol and 20% water was the most appropriate polymerization mixture for preparation of HEMA-MBA copolymer. The elaborated novel procedure of HEMA-MBA hydrophilic monolith preparation allowed for the introduction of higher monomers content compared to earlier literature data. The obtained monolith exhibited lower adsorption of BSA in comparison with the commonly used glycidyl methacrylate-co-ethylene dimethacrylate (GMA-EDMA) material. In the second step, the covalent enzyme attachment on the hydroxyl groups via 1,1'-carbonyldiimidazole activation was performed. Two immobilization techniques were tested. The first approach involved direct trypsin attachment to the hydroxyl groups of two-carbons HEMA chain (microreactor T1). In the other strategy, 5-amino-1-pentanol was employed to form a twelve-atom spacer arm (microreactor TS1). The prepared microreactor s activities and specificities were evaluated using low molecular weight trypsin substrate (Nα-benzoyl-l-arginine ethyl ester (BAEE)) and bovine serum albumin (BSA). The chromatographic analysis of the eluates from T1 and TS1 microreactors indicated that the microreactor T1 showed higher activity toward the BAEE than the microreactor TS1. However, the BSA digestion and subsequent MALDI-TOF MS (Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) analysis of the collected eluates resulted in a sequence coverage of 43.9% and 35.7% in the case of TS1 and T1 microreactors, respectively.

Gold nanoparticles immobilized hydrophilic monoliths with variable functional modification for highly selective enrichment and on-line deglycosylation of glycopeptides

The poly (glycidyl methacrylate-co-poly (ethylene glycol) diacrylate) monoliths modified with gold nanoparticles, with advantages of enhanced reactive sites, good hydrophilicity and facile modification, were prepared as the matrix, followed by variable functionalization with cysteine and PNGase F for glycopeptide enrichment and on-line deglycosylation respectively. By the cysteine functionalized monolithic column, glycopeptides could be efficiently and selectively enriched with good reproducibility based on hydrophilic interaction chromatography (HILIC). Furthermore, the enrichment was specially achieved in weak alkaline environment, with 10 mM NH4HCO3 as the elution buffer, compatible with deglycosylation conditions. Therefore, the glycopeptides could be on-line deglycosylated with high efficiency and throughput by directly coupling the PNGase F functionalized monolithic column with the enrichment column during elution without the requirement of buffer exchange and pH adjustment. By such a method, within only 70-min pretreatment, 196 N-linked glycopeptides, corresponding to 122 glycoproteins, could be identified from 5 μg of human plasma with 14 high-abundant proteins removed, and the N-linked glycopeptides occupied 81% of all identified peptides, achieving to the best of our knowledge, the highest selectivity of HILIC-based methods. All the results demonstrated the high efficiency, selectivity and throughput of our proposed strategy for the large scale glycoproteome analysis.

Preparation of hydrophilic monolithic capillary column by in situ photo-polymerization of N-vinyl-2-pyrrolidinone and acrylamide for highly selective and sensitive enrichment of N-linked glycopeptides

In this study, a novel kind of amide functionalized hydrophilic monolith was synthesized by the in situ photo-polymerization of N-vinyl-2-pyrrolidinone (NVP), acrylamide (AM), and N, N’-methylenebisacrylamide (MBA) in a UV transparent capillary, and successfully applied for hydrophilic interaction chromatography (HILIC) based enrichment of N-linked glycopeptides. With 2μg of the tryptic digests of IgG as the sample, after enrichment, 18 glycopeptides could be identified by MALDI-TOF/TOF MS analysis. Furthermore, with the mixture of BSA and IgG digests ( 10,000:1, m/m) as the sample, 6 N-linked glycopeptides were unambiguously identified after enrichment, indicating the high selectivity and good specificity of such material. Moreover, such a monolithic capillary column was also applied for the N-glycosylation sites profiling of 6μg protein digests from HeLa cells and 1μL human serum. In total, 530 and 262 unique N-glycosylated peptides were identified, respectively, corresponding to 282 and 124N-glycoproteins, demonstrating its great potential for the large scale glycoproteomics analysis.

Ex situ integration of multifunctional porous polymer monoliths into thermoplastic microfluidic chips

A unique method for incorporating functional porous polymer monolith elements into thermoplastic microfluidic chips is described. Monolith elements are formed in a microfabricated mold, rather than within the microchannels, and chemically functionalized off chip before insertion into solvent-softened thermoplastic microchannels during chip assembly. Because monoliths may be trimmed prior to final placement, control of their size, shape, and uniformity is greatly improved over in situ photopolymerization methods. A characteristic trapezoidal profile facilitates rapid insertion and enables complete mechanical anchoring of the monolith periphery, eliminating the need for chemical attachment to the microchannel walls. Off-chip processing allows the parallel preparation of monoliths of differing compositions and surface chemistries in large batches. Multifunctional flow-through arrays of multiple monolith elements are demonstrated using this approach through the creation of a fluorescent immunosensor with integrated controls, and a microfluidic bubble separator comprising a combination of integrated hydrophobic and hydrophilic monolith elements.

Preparation of an Electrochromatographic Stationary Phase Using a New Polymethacrylate Monolith with Chloropropyl Functionality

A new reactive capillary monolith as an alternative to the commonly employed glycidyl methacrylate-based stationary phases in capillary electrochromatography (CEC) applications was synthesized and post-functionalized with charge-bearing groups. For this purpose, a hydrophilic capillary monolith with reactive 3-chloro-2-hydroxypropyl moiety was first obtained by the copolymerization of a new methacrylate-based monomer, 3-chloro-2-hydroxypropyl methacrylate (HPMA-Cl), with a methacrylic crosslinking agent, ethylene glycol dimethacrylate (EDMA). The presence of 3-chloro-2-hydroxypropyl functionality in poly(HPMA-Cl-co-EDMA) monolith allowed the synthesis of monoliths carrying strongly ionizable anionic, cationic or neutral groups such as sulfonic acid, quaternary ammonium or octadecyl, respectively, via simple and single-stage reactions. In the present study, a reactive poly(HPMA-Cl-co-EDMA) capillary monolith was functionalized with sodium bisulfite (NaHSO3) to have a strongly ionizable sulfonic acid group on the monolith. The resulting monolith providing cathodic electroosmotic flow in CEC was successfully used for the separation of phenol derivatives. The theoretical plate numbers up to 63,000 plates/column were achieved. The results showed that a new promising, reactive support that could be functionalized with different chromatographic ligands for different chromatographic applications was obtained in the study.

Synthesis and chromatographic evaluation of sulfobetaine-based capillary zwitterionic hydrophilic monolithic column using a binary porogenic agent of polyethylene glycol/methanol

Sulfobetaine-based capillary zwitterionic hydrophilic monolithic columns were synthesized with a novel binary porogenic agent of polyethylene glycol (PEG)/methanol. The polymer was prepared with (3-(metharyloylamino) propyl) dimethyl (3-sulfopropyl) ammonium hydroxide inner salt (SPP) as monomer, pentaerythritol triacrylate (PETA) as crosslinker, and azobisisobutyronitrile (AIBN) as initiator. In order to optimize the properties, the contents of the polymerization mixture were investigated. The optimum preparation conditions were as follows: the mass ratio of monomer and porogenator = 1:2.5; the mass ratio of SPP and PETA = 1:1 in the monomer; the mass ratio of PEG and methanol = 2:1 in the binary porogenic agent; the content of the initiator (AIBN) = 0.1% (m/m). With the binary porogenic agent of PEG/ methanol addition, good mechanical stability, homogeneous column bed, good permeability and narrow pore size distribution were obtained. In the capillary liquid chromatography mode, the hydrophilic monolith provided column efficiency up to 2.4 x 10(5) plates/m which was much higher than that fabricated by traditional method without PEG/methanol. The columns were used in capillary liquid chromatography and pressurized capillary electrochromatography for the separation of a mixture of phenols, nucleosides and so on.

Neutral, charged and stratified polar monoliths for hydrophilic interaction capillary electrochromatography

Novel polar monoliths were introduced for hydrophilic interaction capillary electrochromatography (HI-CEC). In one case, a neutral polar monolith resulted from the in situ polymerization of glyceryl methacrylate (GMM) and pentaerythritol triacrylate (PETA) in a ternary porogenic solvent. GMM and PETA possess hydroxyl functional groups, which impart the monolith with hydrophilic interaction sites. This monolith is designated as hydroxy monolith. Although the hydroxy monolith is neutral and void of fixed charges on the surface, a relatively strong cathodal EOF was observed due to the electric double layer formed by the adsorption of ions from the mobile phase, producing a bulk mobile phase flow. The second monolith is charged and referred to as AP-monolith that possesses amine/amide functionalities on its surface, and was prepared by the in situ polymerization of N-(3-aminopropyl) methacrylamide hydrochloride (NAPM) and ethylene dimethacrylate (EDMA) in the presence of cyclohexanol, dodecanol and methanol as porogens. Over the pH range studied a strong anodal EOF was observed. The AP-monolith was further exploited in HI-CEC by modifying its surface with neutral mono- and oligosaccharides to produce a series of the so called sugar modified AP-monoliths (SMAP-monolith), which are considered as stratified hydrophilic monoliths possessing a sub-layer of polar amine/amide groups and a top layer of sugar (a polyhydroxy top layer). The SMAP-monoliths can be viewed as a blend of both the hydroxy monolith and the AP-monolith. The polarity of the various monoliths seems to follow the order: hydroxy monolith<AP-monolith<SMAP-monolith. The novel monoliths were characterized over a wide range of elution conditions with a variety of polar solutes including phenols, substituted phenols, nucleic acid bases, nucleosides and nucleotides.

Hydrophilic monolith with ethylene glycol-based grafts prepared via surface confined thiol-ene click photoaddition

Macroporous polymeric monolith bearing thiol-reactive surface functionalities was prepared within micrometer-sized fused silica capillary column by photochemically-driven free radical copolymerization of N-acryloxysuccininimide and ethylene dimethacrylate in the presence of toluene as porogenic solvent, hereafter poly(NAS-co-EDMA), and subsequent surface grafting of allylamine through nucleophilic substitution reaction. The pore surface with pendant allyl moieties was further functionalized via a two-step thiol-ene click reaction with thiol-containing oligo(ethylene glycol) and mercaptoethanol, successively. The surface hydration ability, i.e. hydrophilic character, of the as-obtained monolith was evaluated as a function of the water-content of the liquid fluid environment through electrochromatographic evaluation of the retention properties of the -(O-CH2-CH2)-like surface-functionalized capillary monolith. A major result was that the so called hydrophilic interaction electrochromatographic mode was observed at a given mobile phase composition. An example is given for the separation of phenol-derivatives, with the most hydrophilic one being the most retained. In addition, the hydrophilic interaction based separation allowed for reduced analysis time as compared to the separation observed under reversed-phase separation mode using analogous monolithic stationary phase. Finally, the versatility of the thiol-ene photoaddition approach is demonstrated with an example of C18-like monolith for reversed-phase separation application.

Preparation and evaluation of hydrophilic C18 monolithic sorbents for enhanced polar compound retention in liquid chromatography and solid phase extraction

Hydrophilic C18 monolithic polymer sorbents were synthesized for use in solid phase extraction (SPE) and in capillary liquid chromatography (LC). The approach involved incorporating both hydrophobic and hydrophilic monomers into a monolithic material, by copolymerization of stearyl methacrylate (SMA), poly(ethylene glycol) methyl ether methacrylate (PEGMEMA) and ethylene dimethacrylate (EDMA) in the presence of selected porogens, to produce translucent mesoporous monolithic materials in bulk (SPE) or white macroporous monoliths inside fused silica capillary columns (capillary LC). A capillary column containing one of the hydrophilic C18 monoliths (i.e. poly(SMA-co-PEGMEMA-co-EDMA) with 15% (w/w) PEGMEMA) demonstrated nearly 35% reduction in retention of polycyclic aromatic compounds and greater than 40% increase in retention of phenols compared to a hydrophobic C18 monolithic column. In addition, the hydrophilic monolith demonstrated significantly improved resolution of phenols. Similar monolithic materials prepared in bulk were ground and sieved to obtain 45-65 μm particles with desired rigidity for SPE. To achieve optimum extraction performance for phenols, several parameters, including sample pH and volume, and eluent type and volume, were investigated. Under optimized experimental conditions, the method demonstrated good sensitivity (1.6 ng/mL LOD) and linearity (R(2)>0.97 for 10-200 ng/mL). Again, incorporation of 15% (w/w) PEGMEMA in the monolith increased the extraction efficiency of phenols in water from approximately 20% to 67-92% compared to a hydrophobic C18 monolithic material. Increased wettability of the sorbent by the aqueous sample matrix and the presence of hydrogen-bonding interactions are responsible for the improved retention of polar compounds.

Hydrophilic methacrylate monoliths as platforms for protein microarray

Hydrophilic macroporous monolithic materials based on a copolymer of 2-hydroxyethyl methacrylate with glycerol dimethacrylate was synthesized by photo-initiated free-radical polymerization of monomers in a presence of the low molecular mass porogens, such as cyclohexanol, dodecanol, toluene and heptane, as well as the solutions of hydrophobic polymers, namely, polystyrene of different molecular weights and concentrations in toluene, and poly(dimethyl siloxane) in heptane. The Hildebrand solubility parameters were used to predict the diluent-polymer compatibility. Pore size distribution and surface area characterization have been assessed by mercury intrusion porosimetry; scanning electron microscopy was used to evaluate the differences in macroporous morphology obtained with different porogenic agents. The monolithic materials were covalently attached to a glass surface directly at polymerization step. Monolithic layers were applied as platforms for microarrays to accomplish highly sensitive solid-phase protein analysis. The efficiency of developed microarrays was demonstrated using mouse IgG and goat anti-mouse IgG as a model affinity pair.

Hydrophilic monolith based immobilized enzyme reactors in capillary and on microchip for high-throughput proteomic analysis

A novel kind of hydrophilic monolith based immobilized enzyme reactors (IMERs) was prepared both in UV-transparent capillaries and on glass microchips by the photopolymerization of N-acryloxysuccinimide and poly(ethylene glycol)diacrylate, followed by trypsin immobilization. The performance of capillary IMERs for protein digestion was evaluated by the digestion of myoglobin with the residential time from 12 s to 71 s. With μRPLC–ESI-MS/MS analysis, the obtained sequence coverages were all over 80%, comparable to that obtained by in-solution digestion for 12 h. The nonspecific absorption of BSA on monolithic support was evaluated, and no obvious protein residue was observed by a fluorescence assay. Moreover, no carry-over of the digests on the capillary IMER was found after the digestion of myoglobin (24 μg) and BSA (9 μg), which further demonstrated the good hydrophilicity of such matrix. In addition, an integrated microchip-based system involving on-line protein digestion by microchip-based IMER, peptides separation by nanoRPLC and identification by ESI-MS/MS was established, by which a mixture of standard proteins and one RPLC fraction of Escherichia coli extract were successfully identified, indicating that the hydrophilic monolith based IMER might provide a promising tool for high-throughput proteomic analysis.

Rapid analysis of trace levels of riboflavin and its derivatives with hydrophilic interaction monolith by pressurized capillary electrochromatography with laser induced fluorescence detection

A novel hydrophilic interaction capillary electrochromatographic (HI-CEC) monolith with covalently bonded zwitterionic functional groups was applied for the separation of riboflavins (RF) and its derivatives. With a homemade pressurized capillary electrochromatography-laser induced fluorescence detection (pCEC-LIF) system, trace levels of RF and its derivatives, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), can be baseline separated within 8.0 min in isocratic elution mode. The effect of experimental parameters on separation was investigated. Under the optimum conditions, analytes could be determined over nearly three orders of magnitudes with the detection limits (LODs) as low as 5.0 x 10(-11) mol/L (RF), 8.0 x 10(-10) mol/L (FMN), 2.5 x 10(-9) mol/L (FAD), and the relative standard deviations (RSDs) were less than 8.2%. This method is rapid, simple, repeatable and more sensitive than the most of reported methods, and satisfied results has been achieved in serum sample. Furthermore, it can be further applied for trace analysis of RF and its derivatives in biological fluid and cells.

A new template for the synthesis of porous inorganic oxide monoliths

A hydrophilic monolith, urea-formaldehyde (UF) resin, was for the first time proposed as a hard template for the synthesis of inorganic monoliths. Three kinds of inorganics, silica, zirconia and titania, were successfully prepared by using the new template. Scanning electron microscopy (SEM), nitrogen sorption measurements indicate that the inorganics are the replicas of their templates. Due to the characteristics of low cost, facile control of structure and ease of removal, the UF resin facilitates mass production of inorganic monoliths, which are attractive to industry. In addition, the hydrophilic characteristic of the UF resin makes it possible to use organic free precursors for preparing inorganic monoliths, which should be benign to the environment. The successful synthesis of the zirconia monolith using non-organic precursors confirms this.