Hybrid Monolith Research Articles

Enantiomer Separation of Acidic Chiral Compounds on a tert‐Butylcarbamoylquinine‐Silica Hybrid Monolith by Capillary Electrochromatography

A tert‐butylcarbamoylquinine ( tBuCQUI)‐incorporated silica hybrid monolithic (QUI–SHM) capillary was prepared by “one‐pot” approach via simultaneous sol–gel reaction of tetramethoxysilane and vinyltrimethoxysilane and free radical polymerization of tBuCQUI. A set of acidic chiral drugs were enantioseparated on QUI–SHM in mobile phases consisting of acetonitrile (ACN), methanol (MeOH), acetic acid (AcOH), and triethylamine (TEA). Influences of ACN/MeOH ratio, AcOH/TEA ratio, and their concentrations on enantioseparation were investigated. Baseline separations of enantiomers of all the compounds investigated were achieved with a mobile phase of 60:38 (v/v) ACN/MeOH containing 350 mM AcOH and 30 mM TEA under the applied voltage of −10 kV at 25°C.

Facile “one-pot” synthesis of poly(methacrylic acid)-based hybrid monolith via thiol-ene click reaction for hydrophilic interaction chromatography

A novel sol-gel “one-pot” approach in tandem with a radical-mediated thiol-ene reaction for the synthesis of a methacrylic acid-based hybrid monolith was developed. The polymerization monomers, tetramethoxysilane (TMOS) and 3-mercaptopropyl trimethoxysilane (MPTS), were hydrolyzed in high-concentration methacrylic acid solution that also served as a hydrophilic functional monomer. The resulting solution was then mixed with initiator (2, 2′-azobis (2-methylpropionamide) dihydrochloride) and porogen (urea, polyethylene glycol 20,000) in a capillary column and polymerized in water bath. The column had a uniform porous structure and a good permeability. The evaluation of the monolith was performed by separation of small molecules including nucleosides, phenols, amides, bases and Triton X-100. The calibration curves for uridine, inosine, adenosine and cytidine were determined. All the calibration curves exhibited good linear regressions (R2≥0.995) within the test ranges of 0.5–40μg/mL for four nucleosides. Additionaliy, atypical hydrophilic mechanism was proved by elution order from low to high according to polarity retention time increased with increases in the content of the organic solvent in the mobile phase. Further studies indicated that hydrogen bond and electrostatic interactions existed between the polar analytes and the stationary phase. This was the mechanism of retention. The excellent separation of the BSA digest showed good hydrophility of the column and indicated the potential in separation of complex biological samples.

Recent developments in cyclodextrin functionalized monolithic columns for the enantioseparation of chiral drugs

The use of monolithic supports containing cyclodextrins (CDs) or their derivatives as chiral stationary phases (CSPs) has drawn much attention in the field of enantioseparations. The present review summarized the recent developments in CD functionalized monolithic columns. After introducing their classification in Section 1, various strategies applied to the preparation of the three types of CD functionalized monoliths, i.e. silica based monoliths, organic polymer based monoliths and organic-silica based hybrid monoliths, are thoroughly summarized in Section 2. Particularly, three different preparation strategies for covalently immobilizing CDs onto monoliths, including multi-step strategy, single-step strategy and one-pot strategy, are discussed. In the last section, the applications of CD functionalized monoliths in chiral separation of pharmaceuticals are highlighted.

Effect of gamma rays on the structural and optical properties of a new hybrid monolith silica sucrose xerogel

A new hybrid monolithic silica xerogel containing sucrose has been synthesized via the sol–gel method. The resulting sucrose silica xerogels were exposed to gamma radiation with a dose in the range of 10–100kGy. The effect of gamma rays on the physical and structural properties of sucrose silica xerogels was investigated by Fourier transform infrared spectroscopy (FTIR) and UV visible spectroscopy. The results of FTIR spectroscopy show that the irradiation process causes changes in the network's structure by inducing defects. The UV visible spectra present three main band defects; E′ center, Non-Bridging Oxygen Hole center (NBOHC) and carbonyl radicals in irradiated sucrose silica xerogel samples. Additionally, the results show that the values of optical band gap energy depend on irradiation. Therefore, generated defects suggest that the behavior of sucrose silica xerogels was modified from an insulator (Eg=5.82eV) to a semiconductor (Eg=3.16eV) under gamma irradiation.

Phosphorylated membrane proteome analysis of human neuroblastoma SH-SY5Y cell line

A strategy with the combination of multiprotease digestion and the selective enrichment of phosphopeptides by silica hybrid monolith based immobilized Ti4+ affinity chromatography (Ti4+ -IMAC) was proposed, and applied in the global profiling of phosphorylated membrane proteome of neuroblastoma SH-SY5Y cells. The fraction of membrane proteins was extracted by ultra speed centrifuge, followed by washing with 1 mol/L sodium chloride and 0.1 mol/L sodium carbonate. For digestion, chymotrypsin and pepsin with broader specificity were used as complementary enzymes to trypsin. The phosphopeptides were then selectively enriched by monolithic Ti4+ -IMAC column, and analyzed by nanoflow high performance liquid chromatography and mass spectrometry. A total of 43 phosphoproteins were identified, among which 14 proteins were located on the membrane. All these results demonstrated that the proposed strategy might be promising to promote the in-depth study of neuroblastoma and discover the candidate biomarkers.

Monolithic stationary phases with incorporated fumed silica nanoparticles. Part II. Polymethacrylate-based monolithic column with “covalently” incorporated modified octadecyl fumed silica nanoparticles for reversed-phase chromatography

This study is concerned with the incorporation of surface modified fumed silica nanoparticles (FSNPs) into polymethacrylate based monolithic columns for use in reversed phase chromatography (RPC) of small solutes and proteins. First, FSNPs were modified with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) to yield the “hybrid” methacryloyl fumed silica nanoparticle (MFSNP) monomer. The resulting MFSNP was then mixed with glyceryl monomethacrylate (GMM) and ethylene dimethacrylate (EDMA) in a binary porogenic solvent composed of cyclohexanol and dodecanol, and the in situ copolymerization of MFSNP, GMM and EDMA was performed in a stainless steel column of 4.6 mm i.d. The silanol groups of the hybrid monolith thus obtained were grafted with octadecyl ligands by perfusing the hybrid monolithic column with a solution of 4% w/v of dimethyloctadecylchlorosilane (DODCS) in toluene while the column was maintained at 110°C for 6h (in a heated HPLC oven). One of the originalities of this study was to demonstrate MFSNP as a novel derivatized “hybrid monomer” in making RPC monolithic columns with surface bound octadecyl ligands. In this respect, the RPC behavior of the monolithic column with “covalently” incorporated FNSPs having surface grafted octadecyl ligands was evaluated with alkylbenzenes, aniline derivatives and phenolic compounds. The results showed that the hybrid poly(GMA-EDMA-MFSNP) having surface bound octadecyl ligands exhibited hydrophobic interactions under reversed phase elution conditions. Furthermore, six standard proteins were baseline separated on the column using a 10min linear gradient elution at increasing ACN concentration in the mobile phase at a flow rate of 1.0mL/min using a 10 cm×4.6mm i.d. column. The relative standard deviations (RSDs) for the retention times of the tested solutes were lower than 2.1% and 2.4% under isocratic elution and gradient elution conditions, respectively.

Preparation of cyclodextrin-modified monolithic hybrid columns for the fast enantioseparation of hydroxy acids in capillary liquid chromatography.

Cyclodextrins and their derivatives are one of the most common and successful chiral selectors. However, there have been few publications about the use of cyclodextrin-modified monoliths. In this study, organic hybrid monoliths were prepared by the immobilization of derivatized β-cyclodextrin alone or with l-2-allylglycine hydrochloride to the polyhedral oligomeric silsesquioxane methacryl substituted monolith. The main topic of this study is a combined system with dual chiral selectors (l-2-allylglycine hydrochloride and β-cyclodextrin) as monolithic chiral stationary phase. The effect of l-2-allylglycine hydrochloride concentration on enantioseparation was investigated. The enantioseparation of the four acidic compounds with resolutions up to 2.87 was achieved within 2.5 min on the prepared chiral monolithic column in capillary liquid chromatography. Moreover, the possible mechanism of enantioseparation was discussed.

One‐pot synthesis of a new high vinyl content hybrid silica monolith dedicated to nanoliquid chromatography

A new vinyltrimethoxysilane-based hybrid silica monolith was developed and used as a reversed-phase capillary column. The synthesis of this rich vinyl hybrid macroporous monolith, by cocondensation of vinyltrimethoxysilane with tetramethoxysilane, was investigated using an unconventional (formamide, nitric acid) porogen/catalyst system. A macroporous hybrid silica monolith with 80% in mass of vinyltrimethoxysilane in the feeding silane solution was obtained and compared to a more conventional low vinyl content hybrid monolith with only of 20% vinyltrimethoxysilane. Monoliths were characterized by scanning electron microscopy, (29) Si nuclear magnetic resonance spectroscopy and N2 adsorption-desorption. About 80% of the vinyl precursor was incorporated in the final materials, leading to 15.9 and 61.5% of Si atoms bonded to vinyl groups for 20% vinyltrimethoxysilane and 80% vinyltrimethoxysilane, respectively. The 80% vinyltrimethoxysilane monolith presents a lower surface area than 20% vinyltrimethoxysilane (159 versus 551 m(2) /g), which is nevertheless compensated by a higher vinyl surface density. Chromatographic properties were evaluated in reversed-phase mode. Plots of ln(k) versus percentage of organic modifier were used to assess the reversed-phase mechanism. Its high content of organic groups leads to high retention properties. Column efficiencies of 170 000 plates/m were measured for this 80% vinyltrimethoxysilane hybrid silica monolith. Long capillary monolithic columns (90 cm) were successfully synthesized (N = 120 000).

Clickable Periodic Mesoporous Organosilica Monolith for Highly Efficient Capillary Chromatographic Separation.

A novel clickable periodic mesoporous organosilica monolith with the surface area up to 1707 m(2) g(-1) was in situ synthesized in the capillary by the one-step condensation of the organobridged-bonded alkoxysilane precursor bis(triethoxysilyl)ethylene. With Si-C bonds in the skeleton, the monolith possesses excellent chemical and mechanical stability. With vinyl groups highly loaded and homogeneously distributed throughout the structure, the monolith can be readily functionalized with functional groups by effective thiol-ene "click" chemistry reaction. Herein, with "click" modification of C18, the obtained monolith was successfully applied for capillary liquid chromatographic separation of small molecules and proteins. The column efficiency could reach 148,000 N/m, higher than most reported hybrid monoliths. Moreover, intact proteins could be separated well with good reproducibility, even after the monolithic column was exposed by basic mobile phase (pH 10.0) overnight, demonstrating the great promising of such monolith for capillary chromatographic separation.

Correction: Compressible porous hybrid monoliths: preparation via a low molecular mass gelators-based gel-emulsion approach and exceptional performances

Correction for ‘Compressible porous hybrid monoliths: preparation via a low molecular mass gelators-based gel-emulsion approach and exceptional performances’ by Xiangli Chen et al., J. Mater. Chem. A, 2015, DOI: 10.1039/c5ta08342g.

Synthesis and Surface Reactivity of Vinylized Macroporous Silica Monoliths: One-Pot Hybrid versus Postsynthesis Grafting Strategies.

Different synthesis routes have been implemented to prepare macroporous monoliths with vinyl pendant groups and micrometric skeletons and through-pore sizes. A standard process combining the synthesis of a widely used (methyltrimethoxysilane/tetramethoxysilane) (MTMS/TMOS) hybrid silica monolith and the postsilanization with vinyltrimethoxysilane (VTMS) was used as reference material (Vgr-MTMS). An alternative "one-pot" procedure was used to obtain vinylized hybrid monoliths. Two VTMS/TMOS hybrid based monoliths were successfully prepared starting from 20% (w) and 80% (w/w) of VTMS, respectively, called 20-VTMS and 80-VTMS. Monoliths were characterized by SEM, nitrogen-adsorption isotherm, and (29)Si MAS NMR spectroscopy. One-pot synthesis allowed to obtain higher vinyl contents (15.9 and 61.5 mol % of Si atoms bonded to vinyl groups respectively for 20-VTMS and 80-VTMS) than for the postgrafted one (7.1%). Accessibility of vinyl groups was determined by the extent of bromination reactions followed by FTIR-ATR spectroscopy. Bromination with reaction yields were higher than 80% for all materials (80%, 85%, and 100% for 80-VTMS, 20-VTMS, and Vgr-MTMS respectively), with no diffusion issues The chemical reactivity of the pendant vinyl groups was investigated through radical-mediated thiol-ene reaction and radical-initiated bisulfite addition. Reaction yields for the two VTMS hybrid monoliths were quite lower (4-6%) than those obtained (about 50%) for the Vgr-MTMS monolith. The difference in reactivity was attributed to the steric hindrance of the vinyl moieties at the surface of hybrid materials. However, the lower reactivity of vinyl groups is compensated by their considerably higher surface density. Thus, hybrid monoliths are advantageous over their grafted counterparts, due to their higher hydrolytic stability and to the greater simplicity of the one-pot process. A chromatographic application exemplifies their interest and performances in separation science.

Synthesis and Overall Photophysical Characterization of SiO2:(Ag/SiO2) Nanostructured Sonogel Hybrid Glasses

Bulk SiO 2-based inorganic–inorganic sonogel (SG) hybrid glasses were fabricated with Ag / SiO 2 supported metal nanoparticles (MNPs). The catalyst-free SG route was implemented to produce these optically active nanostructured composites by doping the liquid sol-phase with Ag / SiO 2 synthesized according to the deposition–precipitation method. As prepared Ag / SiO 2-MNPs exhibited particle diameters below 10 nm and homogeneous size distribution. The easy and homogeneous Ag / SiO 2 loading within the micro/mesoporous SiO 2-SG network has evidenced the guest–host chemical affinity of these systems. This fact allowed us to fabricate outstanding chemically, photo-physically and mechanically stable bulk hybrid monoliths with controllable geometry and doping rates, suitable for linear and nonlinear optical (NLO)–spectroscopic characterizations. Indeed, the hosting SG matrix provided an elevated thermal and mechanical stability protecting the reactive Ag nanoparticles from environment conditions, diminishing their tendency to from aggregates and, above all, preserving their pristine photophysical properties. Comprehensive morphological, structural, spectroscopic and NLO characterizations were performed on the obtained SiO 2:( Ag / SiO 2) hybrid composites. Results have shown that the nanocrystalline (NC) properties, multipolar nature and small sizes of the implemented Ag / SiO 2-nanoparticles, together with the bulk guest–host mechanical interactions, play a crucial role for the observation of outstanding spectroscopic and quadratic NLO properties of the developed hybrid systems.

Enantioseparation of basic chiral drugs on a carbamoylated erythromycin-zirconia hybrid monolith using capillary electrochromatography

An organic–inorganic hybrid monolithic column was prepared within the confines of a capillary via a single-step in situ sol–gel approach using zirconium tetrabutoxide as a precursor to compose the inorganic backbone and 3-triethoxysilylpropyl carbamoylated derivative of erythromycin (TEOSPC-ERY) as a co-precursor to introduce the organic chiral selector moiety in the zirconia backbone. The resulting carbamoylated ERY-zirconia hybrid monolith (ERY-ZHM) showed homogeneous morphology with well-defined through pores and was tightly connected with the inner wall of the capillary. The column was employed for capillary electrochromatographic enantioseparation of six basic chiral drugs in mobile phases (MPs) consisting of acetonitrile (ACN) and triethylammonium acetate (TEAA) buffer. The effects of composition of MP and applied voltage on chiral separation were investigated by using propranolol as a representative analyte. The highest resolution (Rs=3.33) was obtained with a MP consisting of 10/90 (v/v) ACN/TEAA buffer (10mM, pH 7), 10kV applied voltage and 25°C capillary temperature. The relative standard deviations for resolution values regarding run to run, day to day, column to column and batch to batch repeatability were 0.41%, 0.89%, 1.80% and 2.26% (for n=3), respectively, indicating satisfactory stability of columns and reproducibility of column preparation process.

Crack-free polydimethylsiloxane–bioactive glass–poly(ethylene glycol) hybrid monoliths with controlled biomineralization activity and mechanical property for bone tissue regeneration

Crack-free organic–inorganic hybrid monoliths with controlled biomineralization activity and mechanical property have an important role for highly efficient bone tissue regeneration. Here, biomimetic and crack-free polydimethylsiloxane (PDMS)–modified bioactive glass (BG)–poly(ethylene glycol) (PEG) (PDMS–BG–PEG) hybrids monoliths were prepared by a facile sol–gel technique. Results indicate that under the assist of co-solvents, BG sol and PDMS and PEG could be hybridized at a molecular level, and effects of the PEG molecular weight on the structure, biomineralization activity, and mechanical property of the as-prepared hybrid monoliths were also investigated in detail. It is found that an addition of low molecular weight PEG can significantly prevent the formation of cracks and speed up the gelation of the hybrid monoliths, and the surface microstructure of the hybrid monoliths can be changed from the porous to the smooth as the PEG molecular weight increases. Additionally, the hybrid monoliths with low molecular weight PEG show the high formation of the biological apatite layer, while the hybrids with high molecular weight PEG exhibit negligible biomineralization ability in simulated body fluid (SBF). Furthermore, the PDMS–BG–PEG 600 hybrid monolith has significantly high compressive strength (32±3MPa) and modulus (153±11MPa), as well as good cell biocompatibility by supporting osteoblast (MC3T3-E1) attachment and proliferation. These results indicate that the as-prepared PDMS–BG–PEG hybrid monoliths may have promising applications for bone tissue regeneration.

Preparation of well-controlled three-dimensional skeletal hybrid monoliths via thiol–epoxy click polymerization for highly efficient separation of small molecules in capillary liquid chromatography

Two kinds of hybrid monoliths were first prepared via thiol–epoxy click polymerization using a multi-epoxy monomer, octaglycidyldimethylsilyl POSS (POSS-epoxy), and two multi-thiols, trimethylolpropanetris(3-mercaptopropionate) (TPTM) and pentaerythritoltetrakis(3-mercaptopropionate) (PTM), respectively, as the precursors. The resulting two hybrid monoliths (assigned as POSS-epoxy–TPTM and POSS-epoxy–PTM) not only possessed high thermal, mechanical and chemical stabilities, but also exhibited well-controlled 3D skeletal microstructure and high efficiency in capillary liquid chromatography (cLC) separation of small molecules. The highest column efficiency reached 182,700N/m (for butylbenzene) on the monolith POSS-epoxy–PTM at the velocity of 0.75mm/s. Furthermore, the hybrid monolith POSS-epoxy–PTM was successfully applied for cLC separations of various samples, not only standard compounds such as alkylbenzenes, PAHs, phenols and dipeptides, as well as intact proteins, but also complex samples of EPA 610 and BSA digest.

Preparation of hybrid monolithic columns via "one-pot" photoinitiated thiol-acrylate polymerization for retention-independent performance in capillary liquid chromatography.

A novel "one-pot" approach was developed for ultrarapid preparation of various hybrid monolithic columns in UV-transparent fused-silica capillaries via photoinitiated thiol-acrylate polymerization of an acrylopropyl polyhedral oligomertic silsesquioxane (acryl-POSS) and a monothiol monomer (1-octadecanethiol or sodium 3-mercapto-1-propanesulfonate) within 5 min, in which the acrylate not only homopolymerizes, but also couples with the thiol. This unique combination of two types of free-radical reaction mechanisms offers a simple way to fabricate various acrylate-based hybrid monoliths. The physical characterization, including scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and thermal gravimetric analysis was performed. The results indicated that the monothiol monomers were successfully incorporated into acryl-POSS-based hybrid monoliths. The column efficiencies for alkylbenzenes on the C18-functionalized hybrid monolithic column reached to 60 000-73 500 plates/m at the velocity of 0.33 mm/s in capillary liquid chromatography, which was far higher than that of previously reported POSS-based columns prepared via thermal-initiated free-radical polymerization without adding any thiol monomers. By plotting the plate height (H) of the alkylbenzenes versus the linear velocity (u) of the mobile phase, the results revealed a retention-independent efficient performance of small molecules in the isocratic elution. These results indicated that more homogeneous hybrid monoliths formed via photoinitiated thiol-acrylate polymerization; particularly, the use of the multifunctional cross-linker possibly prevented the generation of gel-like micropores, reducing mass transfer resistance (C-term). Another sulfonate-containing hybrid monolithic column also exhibited hydrophobicity and ion-exchange mechanism, and the dynamic binding capacity was calculated as 71.1 ng/cm (75 μm i.d.).

Chromatographic efficiency comparison of polyhedral oligomeric silsesquioxanes-containing hybrid monoliths via photo- and thermally-initiated free-radical polymerization in capillary liquid chromatography for small molecules

Monolithic poly(methacrylate epoxy cyclosiloxane-co-polyhedral oligomeric silsesquioxanes) (epoxy-MA–POSS) capillary columns have been prepared via either photo- or thermally-initiated polymerization of the corresponding monomers using a 1-propanol/PEG 400 mixture as porogens. Photochemical polymerization was accomplished by irradiation of the UV-transparent capillary for 10min at room temperature, while thermal polymerization was performed at 55°C, 60°C or 65°C for 18h. The evaluation of chromatographic property for two hybrid epoxy-MA–POSS monoliths was carried out. The results indicate that hybrid monoliths fabricated by photochemical initiation exhibit higher column efficiency (97,000–98,400plates/m) than those synthesized by thermal polymerization (41,100–48,000plates/m) in cLC. The higher efficiency of photo-initiated hybrid monoliths is closely related to lower eddy dispersion (A-term) and mass transfer resistance (C-term).

Histidine-modified organic-silica hybrid monolithic column for mixed-mode per aqueous and ion-exchange capillary electrochromatography.

A novel organic-silica hybrid monolith was prepared through the binding of histidine onto the surface of monolithic matrix for mixed-mode per aqueous and ion-exchange capillary electrochromatography. The imidazolium and amino groups on the surface of the monolithic stationary phase were used to generate an anodic electro-osmotic flow as well as to provide electrostatic interaction sites for the charged compounds at low pH. Typical per aqueous chromatographic behavior was observed in water-rich mobile phases. Various polar and hydrophilic analytes were selected to evaluate the characteristics and chromatographic performance of the obtained monolith. Under per aqueous conditions, the mixed-mode mechanism of hydrophobic and ion-exchange interactions was observed and the resultant monolithic column proved to be very versatile for the efficient separations of these polar and hydrophilic compounds (including amides, nucleosides and nucleotide bases, benzoic acid derivatives, and amino acids) in highly aqueous mobile phases. The successful applications suggested that the histidine-modified organic-silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar and hydrophilic compounds.

Organic amine-grafted carbon quantum dots with tailored surface and enhanced photoluminescence properties

A facile one-step synthesis strategy has been developed for producing fluorescent carbon quantum dots (CQDs) from a kind of Chinese coal, Jincheng anthracite. Surface grafting of the CQDs was completed and systematically investigated by grafting with a series of organic amino molecules. It was found that the solubility and the optical properties of CQDs vary with and depend on its surface chemistry to some degree. Of organic amine-grafted coal-derived CQDs available now, ethylenediamine-grafted CQDs (EDA-CQDs) possess an obviously enhanced photoluminescence (PL) with the quantum yield (QY) as high as 18.6%, being an increase of 24.5 times in comparison with that of the pristine CQDs (0.73%), and have a capability of well dispersing within other polymer matrixes due to their good compatibility after amine-grafting. The hybrid monolith made of amine-grafted CQDs and polymer gelatin exhibits excellent PL properties even at a relatively high concentration of CQDs, indicative of great potential applications in various optical materials and devices.

Preparation of porous graphene oxide–poly(urea–formaldehyde) hybrid monolith for trypsin immobilization and efficient proteolysis

Porous graphene oxide–poly(urea–formaldehyde) (GO–PUF) hybrid monolith was prepared by the in situ polycondensation of the urea–formaldehyde prepolymer solution in the presence of GO sheets and ammonium chloride. The amide groups in the residues of asparagine and glutamine in trypsin was allowed to condense with the residual N-hydroxymethyl groups of PUF in the monolith at low pH to fabricate bioreactors for proteolysis. The morphologies and structures of the prepared materials were investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. The results indicate that both GO–PUF hybrid and trypsin-immobilized GO–PUF hybrid mainly consist of irregular micrometer size flakes and pores that are interconnected to form 3D porous architectures. In addition, the feasibility and performance of the novel capillary bioreactors were demonstrated by the digestion and identification of bovine serum albumin, lysozyme, ovalbumin, and cytochrome c. The digestion time was significantly reduced to less than 10s. The digests were identified by mass spectrometry with results that were comparable to those obtained by 12-h conventional in-solution tryptic digestion.