Organic-inorganic Hybrid Monolithic Column Research Articles

Preparation of a novel amino functionalized ion-imprinted hybrid monolithic column for the selective extraction of trace copper followed by ICP-MS detection

In this work, a novel amino functionalized Cu(II) ion-imprinted organic-inorganic hybrid monolithic column (Cu(II)-IIHMC) was prepared via one-pot co-condensation and the combination of sol-gel and ion-imprinting techniques in a fused capillary. The Cu(II)-IIHMC was used as solid phase microextraction (SPME) matrix followed by inductively coupled plasma-mass spectrometry (ICP-MS) for the analysis of trace Cu(II). The prepared Cu(II)-IIHMC has good mechanical strength, stable imprinting sites and homogeneous structure of network skeleton with large flow-through pores by optimizing the synthesis process. Under the optimized conditions, the Cu(II)-IIHMC can selectively adsorb Cu(II) with the adsorption capacity of 3.13 mg g−1. With enrichment factor of 10-fold, the calibration curve was established in the range of 0.05–50 μg L−1 with r2 of 0.9992 and the detection limit was 0.008 μg L−1 for Cu(II). Compared with the non-imprinted hybrid monolithic column (Cu(II)-NIHMC), the Cu(II)-IIHMC possesses better selectivity, anti-interference ability and adsorption capacity. The Cu(II)-IIHMC can specifically capture the target ion in the presence of competitive ions, with the selectivity coefficients exceeding 39.4. The protocol was validated by analyzing Certified Reference Materials of standard sediment, soil and iron ore, and the results were in good agreement with certified values. Moreover, the proposed in-tube SPME procedure can not only preconcentrate trace Cu(II), but also effectively reduce the matrix effect and powerfully eliminate the interference from the main metals in real samples. Therefore, the developed SPME-ICP-MS method with facile preparation, specific selectivity, high sensitivity and efficient analysis, was applied in the determination of trace Cu(II) in environmental and mineral samples with the recoveries of 89.8–111.8% in all spiked samples.

A hybrid monolithic column based on flower-shaped zeolitic imidazolate framework for efficient capillary microextraction of brominated flame retardants

A novel flower-shaped zeolitic imidazolate framework (ZIF) doped organic-inorganic hybrid monolithic column (ZIF-HMC) was prepared by a simple sol-gel “one-step” method and utilized for efficient capillary microextraction (CME) of four brominated flame retardants. The prepared monolithic was characterized by Fourier transform infrared, scanning electron microscopy, X-ray photoelectron spectroscopy, energy disperse spectroscopy, and N2 adsorption-desorption. The parameters of CME were optimized by orthogonal array design. Under the optimal conditions, the ZIF-HMC showed excellent extraction efficiency, the limit of detection (LODs) and the limit of quantification (LOQs) were in the range of 0.52∼3.1 μg/L and 1.7∼10 μg/L, respectively, and the proposed method demonstrated good recovery (88.8%–116.6%) with the RSD less than 13.6% and a reusability of at least 30 times. The ZIF-HMC possessed great potential for separating organic pollutants and the strategy used here could be extended to prepare other derivatized HMC functionalized monoliths.

Selective recognition of nucleosides by boronate affinity organic-inorganic hybrid monolithic column

Boronic acids are important ligands used to selectively recognize and enrich compounds containing cis-diol groups such as nucleosides. In the present study, organic-inorganic hybrid [POSS-MAH-BPA] monolithic column was prepared for the first time in the literature as a new boronate affinity system for the recognition of nucleosides. The selectivity of the [POSS-MAH-PBA] boronate affinity monolithic column for the recognition of cis-diol containing adenosine nucleoside from its analogue molecule of deoxyadenosine triphosphate, dATP, non-cis-diol containing compound was investigated both by UV and HPLC studies. When the relative selectivity coefficients are compared, the [POSS-MAH-PBA] boronate affinity monolithic column is 4.25 times more selective for adenosine than [POSS-MAH] monolithic column. Besides, to determine endogenous nucleosides in biological fluids, which may serve as non-invasive cancer biomarkers, nucleosides were spiked into the urine solutions and passed through the [POSS-MAH-PBA] boronate affinity monolithic column, and the nucleosides were confirmed by HPLC. The adenosine recognition capability of the [POSS-MAH-PBA] boronate affinity monolithic column with an average enrichment factor of 48.9-fold was apparently superior to that of the [POSS-MAH] monolithic column.Methacryl Polyhedral Oligomeric Silsesquioxanes (POSS-MA) with nano-sized stable 3-dimensional architectures provided the advantage of being used as an adsorbent for the monolithic structure by providing high surface area, 507.60 m2/g, and enabling vinyl groups to function with amino acid-based MAH monomers capable of providing electrons to coordinate PBA. Recovery results of more than 90% for adenosine showed that the [POSS-MAH-PBA] boronate affinity monolithic column could be a promising adsorbent for selective adsorption of cis-diol containing compounds such as nucleosides.

Preparation of gold nanorod-incorporated monolith for solid phase extraction of polycyclic aromatic hydrocarbons.

An organic-inorganic hybrid monolithic column doped with gold nanorods (AuNRs) was prepared and evaluated for solid phase extraction (SPE) of polycyclic aromatic hydrocarbons (PAHs). Excellent dispersibility of AuNRs in binary green porogen system consisting of 1-hexyl-3-methylimidazolium tetrafluoroborate and deep eutectic solvents (DESs) was confirmed by energy dispersive spectrometry (EDS). The particle size of the resulting AuNRs (70-90nm) was thoroughly examined by a transmission electron microscopy (TEM). The redox system including ammonium persulfate (APS) and tetramethylethylenediamine (TEMED) was used to initiate in situ polymerization at 4°C to prepare the hybrid monolith. The mesoporous structure of the AuNR hybrid monoliths was confirmed by scanning electron microscopy (SEM) and nitrogen adsorption. With enrichment factors (EFs) of 150- to 292-fold, the developed method was successfully applied to the determinationof 10 PAHs in wastewater samples. The recoveries at a spiked level were in the range 84.9 to 99.5% with limit of detections (LODs) and relative standard deviations (RSDs) ranging from 0.02 to 0.10μgL-1 and 1.5 to 4.2%, respectively. The correlation coefficients (R2) for the calibration functionobtained were better 0.9991 for the target compounds. Compared tothe AuNR-free monolith, the extraction efficiency of the AuNR-incorporated monolith ismore than two timeshigher. The results indicated that thedoping ofAuNRs is an effective approach to obtain the hybrid monolithic column with good separation ability for PAHs. Graphical abstract.

Development of a novel amine- and carboxyl-bifunctionalized hybrid monolithic column for non-invasive speciation analysis of chromium

A novel amine- and carboxyl-bifunctionalized organic-inorganic hybrid monolithic column (A&C-HMC) was synthesized via one-pot co-condensation of N-(2-aminoethyl)-3-aminopropyltriethoxysilane, carboxyethylsilanetriol sodium salt and tetramethoxysilane with cetyltrimethylammonium bromide and polyethylene glycol 6000 as binary porogens in this work. The introduction of the binary porogens controllably improved the morphology and pore structure of A&C-hybrid monolith (HM) and made the active sites of amine and carboxyl groups more prolific, compared with the monolith prepared with either of porogens. It is found that Cr(VI) and Cr(III) can be selectively adsorbed on A&C-HM under different pH ranges, and eluted by aqueous nitric acid solution completely. The A&C-HMC was used as needle-solid phase microextraction (SPME) matrix for direct separation and enrichment of inorganic chromium species coupled with inductively coupled plasma mass spectrometer without any oxidation/reduction treatment. Various parameters of SPME operation and analytical performance were investigated systematically, and the adsorption mechanism was also discussed and explained in depth. In view of the advantages of facile preparation, low cost, excellent speciation selectivity and high adsorption capacity to Cr(VI) and Cr(III), the A&C-HMC based SPME protocol is a promising alternative for non-disturbed speciation analysis of inorganic chromium in real environmental water samples.

Preparation of thiol- and amine-bifunctionalized hybrid monolithic column via “one-pot” and applications in speciation of inorganic arsenic

A thiol- and amine-bifunctionalized organic-inorganic hybrid monolithic column was prepared for the first time via one-pot co-condensation of 3-mercaptopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane and tetraethylorthosilicate, and utilized for separation and enrichment of inorganic arsenic species. Various parameters of solid phase microextraction (SPME) operation and analytical performance were also investigated systematically. Under the optimum condition, both As(III) and As(V) can be adsorbed over a wide pH range (3.0–8.0) and eluted in turn, in which 3% HNO3 (v/v) was firstly used to selectively release As(V), and then 3% HNO3 with 0.01 mol L−1 KIO3 or 15% mercaptosuccinic acid (MSA) (m/v) to selectively release As(III). Meanwhile, the elution mechanism of As(III) and As(V) was elucidated comprehensively, and notably, the novel eluent, HNO3 + MSA, was recommended for eluting As(III). Therefore, the thiol- and amine-bifunctionalized organic-inorganic hybrid monolithic column as an ideal SPME matrix for the speciation analysis of arsenic in environmental waters has the merits of facile preparation, low cost, high adsorption capacity and selective desorption. In addition, compared with thiol- and amine-bifunctionalized mesoporous silica, the bifunctional hybrid monolith based SPME protocol with less time and reagent consumption is promising to be applied not only to filed sampling but also to on-line analysis.

Preparation and analytical application of novel thiol-functionalized solid extraction matrices: From mesoporous silica to hybrid monolithic capillary column

A comprehensively comparative study of thiol-functionalized mesoporous silica and organic-inorganic hybrid monolithic column was reported, aiming at the separation and enrichment of inorganic arsenic. Thiol-functionalized mesoporous silica was synthesized based on the one-step co-condensation method. At the same time, a novel thiol-functionalized organic-inorganic hybrid monolithic column was synthesized using an unconventional ternary weak basic solvent system via one-step sol-gel process. The approach to prepare monolithic column through mild condition remarkably improved delamination phenomenon of thiol-functionalized hybrid monolithic column easily caused by conventional methods. As(III) can be selectively uptaken by the hybrid monolithic column and homemade syringe-based solid phase extraction device containing mesoporous silica through chelation in a wide range of pH, while As(V) cannot, and then the captured As(III) was eluted by 3% HNO3 (v/v) with 0.01 mol L−1 KIO3. Under the optimized conditions, the extraction recoveries were 91–102% and 93–103% for mesoporous silica and monolithic column, respectively. Although both two materials were ideal solid matrices for the removal and speciation analysis of As(III) in environmental waters, the monolith-based solid phase microextration protocol was more fast and reagent-saving than the other, which endued monolithic columns with more application prospects for trace elemental analysis and speciation. Even so, the exploration of mesoporous silica could efficiently pilot the synthesis of monolithic columns.

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 78000 plates/m.

Preparation of an aptamer based organic–inorganic hybrid monolithic column with gold nanoparticles as an intermediary for the enrichment of proteins

A novel strategy for the preparation of an aptamer based organic-inorganic hybrid affinity monolithic column was developed successfully using gold nanoparticles (GNPs) as an intermediary for a sandwich structure to realize the functional modification of the surface of the monolithic matrix. This monolithic matrix was facilely pre-synthesized via one-step co-condensation. Due to the high surface-to-volume ratio of GNPs and the large specific surface area of the hybrid matrix, the average coverage density of aptamers on the hybrid monolith reached 342 pmol μL(-1). With the combination of an aptamer based hybrid affinity monolithic column and enzymatic chromogenic assay, the quantitation and detection limits of thrombin were as low as 5 nM and 2 nM, respectively. These results indicated that the GNPs attached monolith provided a novel technique to immobilize aptamers on an organic-inorganic hybrid monolith and it could be used to achieve highly selective recognition and determination of trace proteins.

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.

Facile preparation of organic-inorganic hybrid polymeric ionic liquid monolithic column with a one-pot process for protein separation in capillary electrochromatography.

An organic-inorganic hybrid monolithic column based on 1-vinyl-3-dodecylimidazolium bromide (VC12Im(+)Br(-)) has been prepared in a single step by combining radical copolymerization with a non-hydrolytic sol-gel (NHSG) process. The NHSG process was significantly shortened to 6h by using formic acid as catalyst. For comparison, we also prepared polymeric ionic liquid (PIL) monolithic columns by hydrolytic sol-gel and organic polymeric process, respectively. The resulting monolithic columns were characterized by Fourier transform infrared spectra, scanning electron microscopy, and Brunauer-Emmett-Teller. Under the capillary electrochromatography mode, these columns were applied to separate alkylbenzenes, anilines, and proteins, respectively. The results indicated that the NHSG-based hybrid PIL monolithic column exhibited the highest column efficiency among the three types of columns; organic solvent, commonly required by the traditional columns to achieve satisfactory separation efficiency for proteins, was absent in the NHSG-based hybrid PIL monolithic column because of the biocompatibility of the VC12Im(+)Br(-), which was beneficial to analysis of protein containing samples. In order to demonstrate its application potential, the developed NHSG-based hybrid PIL monolithic column was also employed to separate egg white sample.

Synthesis, characterization and application of organic-inorganic hybrid and carbaryl-imprinted capillary monolithic column

Organic-inorganic hybrid and carbaryl-imprinted capillary monolith was synthesized via methacrylic acid(MAA) as functional monomer, γ-methacryloxypropyltrimethoxysilane(γ-MAPS) as crosslinker and carbaryl as template molecule in an acetonitrile/dichloromethane mixture(1:4, volume ratio). With the capillary column obtained from this monolith, three carbamates(carbaryl, fenobucarb and metolcarb) were separated effectively by electrochromatography with the kMIP/kNIP values of 7.57, 1.27 and 1.64, respectively. In 20 mmol/L phosphate buffer solution (pH=3.5) with 30% (volume fraction) of acetonitrile, carbaryl was separated directly from the three-carbamate mixture (carbaryl, fenobucarb and metolcarb) with an effective 15 cm-length imprinted column.

A molecularly imprinted organic-inorganic hybrid monolithic column for the selective extraction and HPLC determination of isoprocarb residues in rice

An IPC-imprinted (IPC is isoprocarb) poly(methacrylic acid)/SiO2 hybrid monolithic column was prepared and applied for the recognition of the template. The hybrid monolithic column was synthesized in a micropipette tip using methyltrimethoxysilane as the inorganic precursor, 3-(methacryloxy)propyltrimethoxysilane as the coupling agent, and ethylene glycol dimethacrylate as the cross-linker. The synthesis conditions, including the porogenic solvent, coupling agent, volume ratio of the inorganic alcoholysate and organic part, were optimized. The prepared monolithic column was characterized by SEM and FTIR spectroscopy. A simple, rapid, and sensitive method for the determination of IPC in rice using the imprinted monolithic column microextraction combined with HPLC was developed. Several parameters affecting the sample pretreatment were investigated, including the eluent, washing solution, and loading sample volume. The linearity of the calibration curve was observed in the range of 9.0-1000 μg/kg for IPC in rice with the correlation coefficient (r2) of 0.9983. The LOD was 3.0 μg/kg (S/N = 3). The assay gave recovery values ranging from 91 to 107%. The proposed method has been successfully applied for the selective extraction and sensitive determination of IPC in rice and a satisfactory result was obtained.

Preparation of 2,4-dichlorophenoxyacetic acid imprinted organic–inorganic hybrid monolithic column and application to selective solid-phase microextraction

An organic-inorganic hybrid molecular imprinting monolith (HMIM) has been prepared, characterized and applied for the determination of 2,4-dichlorophenoxyacetic acid (2,4-D)in rice with high-performance liquid chromatography-photodiodes array detector (HPLC-PAD). By optimizing the polymerization conditions, such as the volume ratio of the inorganic alcoholysate and organic part, the 2,4-D-HMIM was synthesized in a micro pipette tip using acrylamide as the functional monomer, ethylene dimethacrylate as the cross-linker and methanol as the porogenic solvent. The morphology of the monolith was studied by scanning electronmicroscopy and Fourier transform infrared spectra. The imprinted factor of the monolith for 2,4-D reached 3.29. A simple, rapid and sensitive method for the determination of 2,4-D in rice using the HMIM microextraction combined with high-performance liquid chromatography-photodiodes array detector was developed. Some parameters affecting the sample pretreatment were investigated, including the type and volume of eluent, the flow rate and volume of sample solution. The assay exhibited a linear dynamic range of 167-4167μg/kg with the correlation coefficient above 0.9972. The detection limit (at S/N=3) was 50μg/kg. The proposed method was successfully applied for the selective determination of 2,4-D in rice.

A novel organic–inorganic hybrid monolithic column prepared in-situ in a microchip and its application for the determination of 2-amino-4-chlorophenol in chlorzoxazone tablets

γ-Alumina nanoparticles (γ-Al2O3) were introduced to the conventional poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EGDMA) monolith to prepare a novel organic-inorganic hybrid monolith, poly(MAA-co-EGDMA)-Al2O3 monolith. The polymerization was induced in-situ with UV irradiation in an ultraviolet transparent polymethyl methacrylate (PMMA) microfluidic chip. The monolith-based solid phase microextraction system was used for the on-line determination of 2-amino-4-chlorophenol (ACP) in chlorzoxazone tablets coupled with an optical fiber spectrophotometer. Several parameters affecting the adsorption/desorption, including sample pH value, sample flow rate, sampling time, eluent flow rate, and eluting time, were investigated in detail. Under the optimized conditions, limit of detection (LOD) and limit of quantification (LOQ) of the method were calculated to be 2.8 and 9.1µgL−1, respectively, with the relative standard deviation (RSD) of 3.1%.

One-step synthesis of an organic–inorganic hybrid boronate affinity monolithic column with synergistic co-monomers

An organic-inorganic hybrid and synergistic boronate affinity (BA) monolithic column was synthesized by a novel "one-step" approach. We report on the synthesis of a unique organic-inorganic hybrid affinity monolith by using TEOS, the organic silane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane (AEAPTES) and γ-MAPS as the co-precursors, 4-vinylphenylboronic acid as the functionalized monomer, and azobisisobutyronitrile (AIBN) as the initiator. Due to the presence of amino groups in the AEAPTES molecule, the prepared monolith exhibits several attractive properties. The monolith will be more hydrophilic and can bind with cis-diol compounds at neutral pH by a mechanism of intermolecular B-N coordination. The resulting hybrid boronate affinity monoliths have potential applications in specific recognition and enrichment of cis-diol biomolecules under neutral conditions.

On-line solid phase extraction using organic–inorganic hybrid monolithic columns for the determination of trace β-lactam antibiotics in milk and water samples

A rapid and simple method with on­line solid phase extraction (SPE) has been developed for the simultaneous determination of beta-lactam antibiotics (BLAs) (amoxicillin, cephradine, and cefazolin sodium) in aquatic environment and milk. The epoxy-based organic–inorganic hybrid monolithic column was used as SPE sorbent to simultaneously monitor three analytes. The morphology of monolithic column and pressure drop across the columns were characterized. Excellent permeability and high selectivity were obtained. The linear range of the standard curve was from 2.0 to 500ng/mL (r2≥0.999). Precision for inter- and intra-day assay showed acceptable results for quantitative assay with relative standard deviation (RSD) less than 11%. The accuracy and recovery were found to be within the range of 93–103% and 83–105%. The results indicated that the prepared monolithic column could provide excellent reproducibility and implied that the prepared monolith was feasible to be used as an on-line SPE sorbent material.

The preparation of a novel organic–inorganic hybrid monolithic column with sonication-assist and its application

A novel hydroxyl functionalized organic–inorganic hybrid monolithic column for high performance liquid chromatography (HPLC) was synthesized viafree radical copolymerization with sonocation-assist, which could shorten the time of the sol–gel process. Vinyltrimethoxysilane (VTMS) was used as the monomer and vinyl ester resin was used as both the monomer and crosslinker. The conditions of preparation were investigated and the characteristics of the hybrid column were studied by SEM and Fourier transform infrared spectroscopy. The obtained column showed high permeability and low backpressure. The column was used to separate lysozyme from egg white in a short time (6 min) by HPLC, and benzene and its homologs were separated by the hybrid column. In addition, influences on the elution of lysozyme, such as the pH value and the buffer concentration, were studied. Additionally, the lysozyme separated by the hybrid column showed high biological activity, which was assayed by the method of turbidimetry.