Poly(glycidyl methacrylate‐co‐N‐methylolacrylamide‐co‐ethylene dimethacrylate) monolith coupled to high‐performance liquid chromatography for the determination of adenosine phosphates in royal jelly

A polymer monolith microextraction method coupled with high‐performance liquid chromatography was developed for the determination of adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate. The monolithic column was synthesized inside fused‐silica capillaries using thermal initiation free‐radical polymerization with glycidyl methacrylate as the monomer, ethylene dimethacrylate as the cross‐linker, cyclohexanol, and 1‐dodecanol as the porogen. N‐Methylolacrylamide, an important hydrophilic monomer, was incorporated into the polymerization mixture to enhance the hydrophilicity of the poly(glycidyl methacrylate‐co‐ethylene dimethacrylate) column. The obtained poly(glycidyl methacrylate‐co‐N‐methylolacrylamide‐co‐ethylene dimethacrylate) monolith was characterized by scanning electron microscopy, Fourier‐transform infrared spectra, and X‐ray photoelectron spectroscopy. Optimum conditions for the preconcentration and separation of the target adenosines were also investigated. Under the optimum conditions, we obtained acceptable linearities, low limits of detection, and good relative standard deviations. The developed polymer monolith microextraction with high‐performance liquid chromatography method exhibited a good performance with recovery values in the range of 76.9?104.7% when applied to the determination of the adenosines in five royal jelly samples.     

Combining poly (methacrylic acid‐co‐ethylene glycol dimethacrylate) monolith microextraction and octadecyl phosphonic acid‐modified zirconia‐coated CEC with field‐enhanced sample injection for analysis of antidepressants in human plasma and urine

A method based on poly (methacrylic acid‐co‐ethylene glycol dimethacrylate) monolith microextraction and octadecylphosphonic acid‐modified zirconia‐coated CEC followed by field‐enhanced sample injection preconcentration technique was proposed for sensitive CE‐UV analysis of six antidepressants (doxepin, clozapine, imipramine, paroxetine, fluoxetine and chlorimipramine) in human plasma and urine. A poly(methacrylic acid‐co‐ethylene glycol dimethacrylate) monolithic capillary column was introduced for the extraction of antidepressants from urine and plasma samples. The hydrophobic main chains and acidic pendant groups of the monolithic column make it a superior material for extraction of basic analytes from aqueous matrix. After extraction, the desorption solvent, which normally provided an excellent medium to ensure direct compatibility for field‐enhanced sample injection in CE, was analyzed by CE directly. By the use of alkylphosphonate‐modified zirconia‐coated CEC for separation of the basic compounds of antidepressants, high separation efficiency and resolution were achieved because that both hydrophobic interaction between analytes and alkylphosphonate‐modified zirconia coat and electrophoretic effect work on the separation of antidepressants. The best separation was achieved using a buffer composed of 0.3 M ammonium acetate (adjusted to pH 4.5 with 1 M acetic acid) and 35% ACN v/v, with a temperature and voltage of 20°C and 20 kV, respectively. By applying both preconcentration procedures, LODs of 11.4–51.5 and 3.7–17.0 μg/L were achieved for the six antidepressants in human plasma and urine, respectively. Excellent method of reproducibility was found over a linear range of 50–5000 μg/L in plasma and urine sample.     

Preparation of metal‐organic framework UiO‐66‐incorporated polymer monolith for the extraction of trace levels of fungicides in environmental water and soil samples

A zirconium terephthalate metal‐organic framework‐incorporated poly(N‐vinylcarbazole‐co‐divinylbenzene) monolith was fabricated in a capillary by a thermal polymerization method. The optimized monolith had a homogeneous structure, good permeability, and stability. The monolith could be used for the effective enrichment of fungicides through π‐π interactions, electrostatic forces, and hydrogen bonds. The potential factors that affect the extraction efficiency, including ionic strength, solution pH, sample volume, and eluent volume, were investigated in detail. The monolith‐based in‐tube solid‐phase microextraction coupled with ultra‐high‐performance liquid chromatography and high‐resolution Orbitrap mass spectrometry was performed for the analysis of five fungicides (pyrimethanil, tebuconazole, hexaconazole, diniconazole, and flutriafol) in environmental samples. Under the optimized conditions, the linear ranges were 0.005–5 ng/mL for pyrimethanil, 0.01–5 ng/mL for flutriafol, and 0.05–5 ng/mL for other fungicides, respectively, with coefficients of determination ≥0.9911. The limits of detection were 1.34–14.8 ng/L. The columns showed good repeatability (relative standard deviations ≤9.3%, n = 5) and desirable column‐to‐column reproducibility (relative standard deviations 5.3–9.4%, n = 5). The proposed method was successfully applied for the simultaneous detection of five fungicides in water and soil samples, with recoveries of 90.4–97.5 and 84.0–95.3%, respectively.     

Preparation and evaluation of a sulfoalkylbetaine‐based zwitterionic monolithic column for CEC of polar analytes

A novel polymethacrylate‐based monolithic column with covalently bonded zwitterionic functional groups was prepared by in situ copolymerization of N,N‐dimethyl‐N‐methacryloxyethyl N‐(3‐sulfopropyl) ammonium betaine (SPE), pentaerythritol triacrylate (PETA), and vinylsulfonic acid (VS) in a binary porogenic solvent consisting of cyclohexanol and ethylene glycol. This monolith was developed as a separation column for CEC. While SPE functioned as both an electrostatic interaction stationary phase and the polar ligand provider, VS was employed to generate EOF. PETA, which has much more hydrophilicity due to a hydroxyl sub‐layer, was used to replace ethylene dimethacrylate as a cross‐linker. The monolith provided an adequate EOF when VS level was maintained at 0.6% w/w. Different monolithic stationary phases were easily prepared by adjusting the ratio of PETA/SPE in the polymerization solution as well as the composition of the porogenic solvent. The observed RSD were ≤3.6, ≤4.3 and ≤5.6% for the EOF velocity, retention time, and column efficiency, respectively. The column efficiencies greater than 145 000 theoretical plates/m for thiourea and 132 000 theoretical plates/m for charged cytidine were obtained. The poly(SPE‐co‐PETA‐co‐VS) monolith showed good selectivity for neutral and charged polar analytes. It was found that the separation mechanism of charged polar solutes was attributed to a mixed mode of hydrophilic interaction and electrostatic interaction, as well as electrophoresis. No peak tailing was observed for the separation of basic compounds, such as basic nucleic acid bases and nucleoside on the monolith.     

Development of a solid‐phase microextraction fiber coated with poly(methacrylic acid‐ethylene glycol dimethacrylate) and its application for the determination of chlorophenols in water coupled with GC

A solid‐phase microextraction (SPME) fiber coated with poly(methacrylic acid‐ethylene glycol dimethacrylate) coupled to GC with a micro electron‐capture detector was developed for the determination of four chlorphenols in water samples for the first time. A novel and simple method for the preparation of this novel SPME fiber was proposed by copolymerization of methacrylic acid and ethylene glycol dimethacrylate in an appropriate solvent using a glass capillary as a “mold”. The factors affecting the polymerization were optimized in detail. Furthermore, the extraction performance of the poly(methacrylic acid‐ethylene glycol dimethacrylate) fiber was evaluated. Moreover, experimental headspace‐SPME parameters, such as extraction temperature, extraction time, salt concentration, stirring speed, and pH, were optimized by orthogonal array experimental designs. Under the optimized conditions, the target analytes were linear in the range of 0.2–50 ng/mL, and the correlation coefficients were all greater than 0.99. RSD was less than 8.9%, and the detection limits were in the range of 0.1–10 ng/L. Four cholorphenols were detected from tap and lake water samples using the proposed method, with the recoveries of spiked natural water samples were ranged from 91.8 to 110.8, and 90.6 to 111.4% for tap and lake water samples, respectively.     

Development of a γ‐alumina‐ nanoparticle‐functionalized porous polymer monolith for the enrichment of Sudan dyes in red wine samples

Monolithic materials were synthesized in capillaries by in situ polymerization with N‐isopropylacrylamide, glycidyl methacrylate, and ethylene dimethacrylate as the monomers, and methanol and PEG as the porogens. With γ‐alumina nanoparticles attached to the surface of the porous monolithic column via epoxide groups, a novel polymer monolith microextraction (PMME) material was prepared with a good mechanical stability and a high extraction capacity. SEM and X‐ray photoelectron spectroscopy were employed to characterize the modified monolithic column, demonstrating that γ‐alumina nanoparticles were effectively functionalized onto the monolithic column. In addition, a new method was developed for the analysis of Sudan I–IV dyes using PMME coupled with HPLC. In order to obtain the optimum extraction efficiency, the PMME conditions including desorption solvent type, sample pH, sample volume, sample flow rate, and eluent flow rate were investigated. Under the optimum conditions, we obtained acceptable linearities, low LODs, and good intra‐ and interday RDSs. When applied to the determination of Sudan I–IV dyes in red wine samples, satisfactory recoveries were obtained in the range of 84.0–115.9%.     

A poly (4‐vinylpridine‐co‐ethylene glycol dimethacrylate) monolithic concentrator for in‐line concentration‐capillary electrophoresis analysis of phenols in water samples

A poly(4‐vinylpridine‐co‐ethylene glycol dimethacrylate) monolith was synthesized in a capillary and constructed as a concentrator for the in‐line polymeric monolith microextraction coupling with capillary electrophoresis. The integrated system was then used for the simultaneous determination of five trace phenols (2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2‐chlorophenol, and 2,4‐dichlorophenol) in water samples. The experimental parameters for in‐line solid‐phase extraction, such as composition and volume of the elution plug, pH of sample solution, and the time for sample loading were optimized. The sensitivity for the mixture of phenols (2‐nitrophenol, 3‐nitrophenol, 4‐nitrophenol, 2‐chlorophenol, and 2,4‐dichlorophenol) enhanced to 615–2222 folds at the optimum condition was compared to the sensitivity for a normal hydrodynamic injection in capillary electrophoresis. Linearity ranged from concentration of 10–500 ng mL^?1(R² > 0.999) for all five phenols with the detection limits of 1.3–3.3 ng mL^?1. In tap, snow and Yangtze River water spiked with 20 ng mL^?1 and 200 ng mL^?1, respectively, the recoveries of 84–105% were obtained. It has been demonstrated that this work has great potential for the analysis of phenols in genuine water samples.     

Polymer monolith microextraction online coupled to hydrophilic interaction chromatography/mass spectrometry for analysis of β2‐agonist in human urine

An analytical method based on online combination of polymer monolith microextraction (PMME) technique with hydrophilic interaction LC (HILIC)/MS is presented. The extraction was performed with a poly(methacrylic acid‐co‐ethylene glycol dimethacrylate) monolithic column while the subsequent separation was carried out on a Luna silica column by HILIC. After 1:1 v/v dilution with 20 mM phosphate solution at pH 7.0 and centrifugation, urine sample was directly used for extraction. After optimization, 85% ACN (containing 0.3% formic acid v/v) was used for rapid online elution, which was also the mobile phase in HILIC to avoid band broadening during separation or carry‐over that was usually observed in PMME‐RP LC system. Online automation of extraction and separation procedures was realized under the control of a program in this study. The developed method was applied to rapid and sensitive monitoring of three β₂‐agonist traces in human urine. The LODs (S/N = 3) of the method were found to be 0.05–0.09 ng/mL of β₂‐agonists in urine. The recoveries of three β₂‐agonists spiked in five different urine samples ranged from 79.8 to 119.8%, with RSDs less than 18.0%.     

Preparation of molecularly imprinted polymeric fibers using a single bifunctional monomer for the solid‐phase microextraction of parabens from environmental solid samples

In this study, molecularly imprinted polymer fibers for solid‐phase microextraction have been prepared with a single bifunctional monomer, N,O‐bismethacryloyl ethanolamine using the so‐called “one monomer molecularly imprinted polymers” method, replacing the conventional combination of functional monomer and cross‐linker to form high fidelity binding sites. For comparison, imprinted fibers were prepared following the conventional approach based on ethylene glycol dimethacrylate as cross‐linker and methacrylic acid as monomer. The recognition performance of the new fibers was evaluated in the solid‐phase microextraction of parabens, and from this study it was concluded that they provided superior performance over conventionally formulated fibers. Ultimately, real‐world environmental testing on spiked solid samples was successful by the molecularly imprinted solid‐phase microextraction of samples, and the relative recoveries obtained at enrichment levels of 10 ng/g of parabens were within 78–109% for soil and 83–109% for sediments with a relative standard deviation <15% (n = 3).     

Preparation of a polymer monolith modified with delaminated layered double hydroxides for the microextraction of β‐agonists

In the present study, a novel poly(acrylamide‐co‐N‐isopropylacrylamide‐co‐ethylene dimethacrylate) monolithic column modified with saline‐modified delaminated layered double hydroxides was developed and exploited as the stationary phase in the polymer monolith microextraction of β‐agonists. Transmission electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, and thermal gravimetric analysis with derivative thermogravimetric determination were employed to characterize the monoliths. By coupling with high‐performance liquid chromatography determinations, extraction parameters affecting the extraction efficiency, including sample volume, flow rate, sample pH, eluent volume, and eluent flow rate were investigated with an orthogonal experiment design, L₁₆ (4⁵). Results demonstrated that under the optimal experimental conditions, low limits of detection in the range of 0.025–0.280 ng/mL were obtained with relative standard deviations in the range of 4.3–7.6% (intraday) and 6.7–8.8% (interday). When the developed method was applied to the analysis of β‐agonists in pork samples, recovery values were obtained in the range of 80.5−108.6%.     

Selective extraction based on poly(MAA‐VB‐EGMDA) monolith followed by HPLC for determination of hordenine in plasma and urine samples

Hordenine is an active compound found in several foods, herbs and beer. In this work, a novel sorbent was fabricated for selective solid‐phase extraction (SPE) of hordenine in biological samples. The organic polymer sorbent was synthesized in one step in the plastic barrel of a syringe by a pre‐polymerization solution consisting of methacrylic acid (MAA), 4‐vinylphenylboronic acid (VB) and ethylene glycol dimethacrylate (EGDMA). The conditions for preparation were optimized to generate a poly(MAA‐VB‐EGMDA) monolith with good permeability. The monolith exhibited good enrichment efficiency towards hordenine. By using tyramine as the internal standard, a poly(MAA‐VB‐EGMDA)‐based SPE‐HPLC method was established for analysis of hordenine. Conditions for SPE, including volume of eluting solvent, pH of sample solution, sampling rate and sample volume, were optimized. The proposed SPE‐HPLC method presented good linearity (R² = 0.9992) within 10–2000 ng/mL and the detection limits was 3 ng/mL, which is significantly more sensitive than reported methods. The method was also applied in plasma and urine samples; good capability of removing matrices was observed, while hordenine in low content was well extracted and enriched. The recoveries were from 90.6 to 94.7% and from 89.3 to 91.5% for the spiked plasma and urine samples, respectively, with the relative standard deviations <4.7%. Copyright © 2014 John Wiley & Sons, Ltd.     

Boronate affinity monolithic column incorporated with graphene oxide for the in‐tube solid‐phase microextraction of glycoproteins

A poly(vinylphenylboronic acid–ethylene glycol dimethacrylate) monolithic material incorporated with graphene oxide was synthesized inside a poly(ether ether ketone) tube. This tube with boronate affinity monolith was coupled with a high‐performance liquid chromatography system through a six‐port valve to construct an online solid‐phase microextraction with high‐performance liquid chromatography system. The performance of this solid‐phase microextraction with high‐performance liquid chromatography system was demonstrated by standard glycoprotein in aqueous samples, namely, horseradish peroxidase. Some parameters that affect the extraction performance were investigated, including sampling rate, pH of sample solution, and sampling volume. Under the optimized conditions, the developed method showed high extraction efficiency toward horseradish peroxidase. The addition of graphene oxide greatly increased the extraction efficiency of boronate affinity monolith for horseradish peroxidase. The limit of detection of the proposed method was as low as 0.01 μg/mL by using ultraviolet detection. The recognition specificity was also evaluated by analyzing the mixture of bovine serum albumin (nonglycoprotein) and horseradish peroxidase. The results showed that this material could selectively extract horseradish peroxidase from the mixture, indicating its good specificity toward glycoproteins. The proposed method was further applied for analyzing rat plasma samples spiked with horseradish peroxidase. Good recovery and repeatability were obtained.     

Preparation of a monolith functionalized with zinc oxide nanoparticles and its application in the enrichment of fluoroquinolone antibiotics

This study describes the enrichment ability of ZnO‐modified methacrylic acid‐co‐ethylene dimethacrylate polymer monoliths as stationary phases for the simultaneous determination of antibiotics (ofloxacin, ciprofloxacin, enoxacin, and pefloxacin) combined with high‐performance liquid chromatography. The prepared monolith was characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier‐transformed infrared spectroscopy, and thermogravimetric analysis. The polymer monolith microextraction method has been applied to the enrichment of fluoroquinolone antibiotics and satisfactory results were obtained in the analysis of water samples. Compared with the conventional methacrylic acid based monolith, the developed monolith exhibited a higher enrichment capacity because of the introduction of zinc oxide into the preparation process.     

Ti (IV) attached‐phosphonic acid functionalized capillary monolith as a stationary phase for in‐syringe‐type fast and robust enrichment of phosphopeptides

In this study, poly(vinylphosphonic acid‐co‐ethylene dimethacrylate), poly(VPA‐co‐EDMA) capillary monolith was synthesized as a starting material for obtaining a stationary phase for microscale enrichment of phosphopeptides. The chelation of active phosphonate groups with Ti (IV) ions gave a macroporous monolithic column with a mean pore size of 5.4 μm. The phosphopeptides from different sources were enriched on Ti (IV)‐attached poly(VPA‐co‐EDMA) monolith using a syringe‐pump. The monolithic capillary columns exhibited highly sensitive/selective enrichment performance with phosphoprotein concentrations as low as 1.0 fmol/mL. Six different phosphopeptides were detected with high intensity by the treatment of β‐casein digest with the concentration of 1.0 fmol/mL, using Ti (IV)@poly(VPA‐co‐EDMA) monolith. Highly selective enrichment of phosphopeptides was also successfully carried out even at trace amounts, in a complex mixture of digested proteins (molar ratio of β‐casein to bovine serum albumin, 1:1500) and three phosphopeptides were successfully detected. Four highly intense signals of phosphopeptides in human serum were also observed with high signal‐to‐noise ratio and a clear background after enrichment with Ti (IV)@poly(VPA‐co‐EDMA) monolith. It was concluded that the capillary microextraction system enabled fast, efficient and robust enrichment of phosphopeptides from microscale complex samples. The whole enrichment process was completed within 20 min, which was shorter than in the previously reported studies.     

Development of multiple monolithic fiber solid‐phase microextraction and liquid chromatography–tandem mass spectrometry method for the sensitive monitoring of aminoglycosides in honey and milk samples

A simple and sensitive method for the simultaneous extraction and determination of six aminoglycosides in honey and milk samples was developed using multiple monolithic fiber solid‐phase microextraction and liquid chromatography with tandem mass spectrometry. The multiple monolithic fibers based on poly(methacrylic acid‐co‐ethylenedimethacrylate) monolith as the extraction medium was used to concentrate target analytes. Because there were abundant carboxyl groups in the monolith, the monolithic fibers could extract aminoglycosides effectively through cation‐exchange and hydrophobic interactions. To obtain optimum extraction performance, several extraction parameters including desorption solvent, adsorption and desorption time, pH value and ionic strength in sample matrix, were investigated in detail. Under the optimized extraction conditions, the limits of detection of the proposed method were 0.10–0.30 and 0.23–0.59 μg/kg for honey and milk samples, respectively. Satisfactory linearity was achieved for analytes with the coefficients of determination above 0.99. At the same time, the developed method showed acceptable method repeatability and reproducibility. Finally, the proposed method was successfully applied to the determination of aminoglycosides in real honey and milk samples. Recoveries obtained for the determination of six target analytes in spiking samples ranged from 67.9 to 110%, and the relative standard deviations were in the range of 1.2–11%.     

Comparative evaluation of a one‐pot strategy for the preparation of β‐cyclodextrin‐functionalized monoliths: Effect of the degree of amino substitution of β‐cyclodextrin on the column performance

To further evaluate the feasibility and applicability of the one‐pot strategy in monolithic column preparation, two novel β‐cyclodextrin‐functionalized organic polymeric monoliths were prepared using two β‐cyclodextrin derivatives, i.e. mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin and heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin. In this improved method, mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin or heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin reacted with glycidyl methacrylate to generate the corresponding functional monomers and were subsequently copolymerized with ethylene dimethacrylate. The polymerization conditions for both monoliths were carefully optimized to obtain satisfactory column performance with respect to column efficiency, reproducibility, permeability, and stability. The obtained poly(glycidyl methacrylate‐mono(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) and poly(glycidyl methacrylate‐heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) monoliths exhibited a uniform structure, good permeability, and mechanical stability as indicated by scanning electron microscopy and micro‐high‐performance liquid chromatography experimental results. Because of the probable existence of multi‐glycidyl methacrylate linking spacers on the poly(glycidyl methacrylate‐heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin‐co‐ethylene dimethacrylate) monolith, the effect of the ratio of glycidyl methacrylate/heptakis(6‐amino‐6‐deoxy)‐β‐cyclodextrin was especially studied, and satisfactory reproducibility could still be achieved by strictly controlling the composition of the polymerization mixture. To investigate the effect of the degree of amino substitution of β‐cyclodextrin on column performance, a detailed comparison of the two monoliths was also carried out using series of analytes including small peptides and chiral acids. It was found that the β‐cyclodextrin‐functionalized monolith with mono‐glycidyl methacrylate linking spacers demonstrated better chiral separation performance than that with multi‐glycidyl methacrylate linking spacers.     

Polymeric monolith column composited with multiwalled carbon nanotubes‐β‐cyclodextrin for the selective extraction of psoralen and isopsoralen

A polymeric column that contains multiwalled carbon nanotubes‐β‐cyclodextrin composite was developed. The composite was wrapped into the poly(butyl methacrylate‐ethylene dimethacrylate) monolith column (0.76 mm id and 10 cm in length). The column was then applied for the online solid‐phase microextraction of psoralen and isopsoralen from Fructus Psoraleae. Following microextraction, the coumarins were quantified by high‐performance liquid chromatography with C₁₈ separation column and UV detection. The effects of sample flow rate, sample volume, and pH value were optimized. The method showed low limits of detection (20 pg/mL, S/N = 3) for both psoralen and isopsoralen. Finally the method was successfully applied to the determination of psoralen and isopsoralen in spiked herb extracts and rat plasma where it gave recoveries that ranged between 93.2 and 102.1%. The empty hydrophobic cavities of β‐cyclodextrin and the hydrophobicity of multiwalled carbon nanotubes provided specific extraction capability for psoralen and isopsoralen.     

Fabrication of an ionic‐liquid‐based polymer monolithic column and its application in the fractionation of proteins from complex biosamples

An ionic‐liquid‐based polymer monolithic column was synthesized by free radical polymerization within the confines of a stainless‐steel column (50 mm × 4.6 mm id). In the processes, ionic liquid and stearyl methacrylate were used as dual monomers, ethylene glycol dimethacrylate as the cross‐linking agent, and polyethylene glycol 200 and isopropanol as co‐porogens. Effects of the prepolymerization solution components on the properties of the resulting monoliths were studied in detail. Scanning electron microscopy, nitrogen adsorption–desorption measurements, and mercury intrusion porosimetry were used to investigate the morphology and pore size distribution of the prepared monoliths, which showed that the homemade ionic‐liquid‐based monolith column possessed a relatively uniform macropore structure with a total macropore specific surface area of 44.72 m²/g. Compared to a non‐ionic‐liquid‐based monolith prepared under the same conditions, the ionic‐liquid‐based monolith exhibited excellent selectivity and high performance for separating proteins from complex biosamples, such as egg white, snailase, bovine serum albumin digest solution, human plasma, etc., indicating promising applications in the fractionation and analysis of proteins from the complex biosamples in proteomics research.     

Facile preparation of a polydopamine‐based monolith for multiple monolithic fiber solid‐phase microextraction of triazine herbicides in environmental water samples

A new multiple monolithic fiber solid‐phase microextraction using a polydopamine‐based monolith as the extraction medium is proposed. The monolith was synthesized by facile in situ copolymerization of N‐methacryldopamine and dual cross‐linkers (divinylbenzene/ethylenedimethacrylate) in the presence of N ,N‐dimethylformamide. The effect of the contents of N‐methacryldopamine and porogen in the polymerization mixture on the extraction performance was investigated thoroughly. A series of characterization studies was performed to validate the structure and properties of the monolith. The prepared multiple monolithic fibers were used for the extraction of triazine herbicides in environmental water samples. After the optimization of the extraction parameters, a convenient, sensitive, cost‐effective, and environmentally friendly method for the determination of trace triazine herbicides in water samples was developed by coupling multiple monolithic fibers solid‐phase microextraction with high‐performance liquid chromatography and diode array detection. The results indicated that the limits of detection and quantification for the target compounds were 0.031–0.14 and 0.10–0.45 μg/L, respectively. Good precision and reproducibility were obtained with the relative standard deviations below 10%. The developed method was applied to the analysis of the triazine herbicides in different water samples (lake, river, and farmland waters). The recoveries of the method were in the range between 79.6 and 117%.     

Semi‐micro reversed‐phase liquid chromatography for the separation of alkyl benzenes and proteins exploiting methacrylate‐ and polystyrene‐based monolithic columns

Monolithic columns were synthesized inside 1.02 mm internal diameter fused‐silica lined stainless‐steel tubing. Styrene and butyl, hexyl, lauryl, and glycidyl methacrylates were the functional monomers. Ethylene glycol dimethacrylate and divinylbenzene were the crosslinkers. The glycidyl methacrylate polymer was modified with gold nanoparticles and dodecanethiol (C₁₂). The separation of alkylbenzenes was investigated by isocratic elution in 60:40 v/v acetonitrile/water. The columns based on polystyrene‐co‐divinylbenzene and poly(glycidyl methacrylate)‐co‐ethylene glycol dimethacrylate modified with dodecanethiol did not provide any separation of alkyl benzenes. The poly(hexyl methacrylate)‐co‐ethylene glycol dimethacrylate and poly(lauryl methacrylate)‐co‐ethylene glycol dimethacrylate columns separated the alkyl benzenes with plate heights between 30 and 60 μm (50 μL min^?1 and 60°C). Similar efficiency was achieved in the poly(butyl methacrylate)‐co‐ethylene glycol dimethacrylate column, but only at 10 μL min^?1 (0.22 mm s^?1). Backpressures varied from 0.38 MPa in the hexyl methacrylate to 13.4 MPa in lauryl methacrylate columns (50 μL min^?1 and 60°C). Separation of proteins was achieved in all columns with different efficiencies. At 100 μL min^?1 and 60°C, the lauryl methacrylate columns provided the best separation, but their low permeability prevented high flow rates. Flow rates up to 500 μL min^?1 were possible in the styrene, butyl and hexyl methacrylate columns.