Polymer Monolith Research Articles

Bio-based rigid high-density polyurethane foams as a structural thermal break material

Sustainable development of building industry implies increasing usage of green materials. With this aim and for the intended application as a structural thermal break material, rigid high-density polyurethane foams have been manufactured using polyols derived from renewable resources - tall oil fatty acids. Thermal conductivity, compressive strength and stiffness of the foams of density ranging from ca. 100 to 680 kg/m3 have been determined. Comparison of the bio-based foams with reference foams derived from petrochemical resources demonstrated similar performance characteristics thus suggesting that bio-based foams can also serve as structural thermal break materials. Analytical models are shown to enable estimation of density dependence of the thermal and mechanical properties of foams using the respective experimentally determined characteristics of the monolithic polyurethane polymer.

On-line enrichment and determination of aristolochic acid in medicinal plants using a MOF-based composite monolith as adsorbent

In this study, modified UiO-66-NH2 and N-methylolacrylamide (NMA) were used as common monomers to prepare a metal organic framework (MOF)-based composite monolith through in-situ polymerization, which was used as a new adsorbent to purify and enrich aristolochic acid-I (AA-I) in medicinal plants. The MOF-based composite monolithic column was characterized by nitrogen adsorption–desorption isotherm, mercury intrusion porosimetry and scanning electron microscopy (SEM). The adsorption ability of MOF-based composite monolith for AA-I was compared with that of the polymer monolith without MOF added. The results proved that the addition of UiO-66-NH2 can increase both the specific surface area and the permeability of the monolith. Moreover, the adsorption amount of AA-I on the monolith improved. This proposed on-line solid phase extraction (SPE) method showed good linear relationship in the range 0.044 ~ 400 μg/mL with r = 0.9994; the limit of detection (LOD) was 13.08 ng/mL and the limit of quantification (LOQ) was 44.00 ng/mL; the intra-day and inter-day accuracies were less than 0.97%; the inter-column accuracies was less than 6.11%; the recovery was in the range of 91.11%~106.48%. The method was found to be easy, accurate and convenient for on-line enrichment and purification of AA-I in medicinal plants.

Porous silica and polymer monolith architectures as solid-state optical chemosensors for Hg2+ ions

We demonstrate a simple strategy to concoct a competent solid-state opto-chemosensor for the selective and sensitive visual detection of Hg2+ ions. The sensor fabrication involves the utilization of indigenously prepared mesoporous silica and polymer monoliths as probe anchoring templates and 8-hydroxy-7-(4-n-butylphenylazo) quinoline (HBPQ) as the chromo-ionophoric probe for Hg2+ sensing. Both the monoliths are designed with discrete structural and morphological features to serve as efficient host templates. The structural and surface features of the monoliths are characterized using p-XRD, TEM, SEM, SAED, EDAX, XPS, and N2 isotherm analysis. The synergetic features of monolith structural hierarchy along with the probe's selective chelating ability enable rapid signal response and remarkable ion selectivity for Hg2+. The solid-state sensors evince a linear signal response from 0.6 to 150μg/L for Hg2+ recognition, with superior data authenticity and replication that is preceded by an RSD value of ≤ 2.25% when tested with real water samples.Graphical abstract Mesoporous silica and polymer monolith architects hosting HBPQ probe molecules demonstrate an excellent visual sensing of ultra-trace (μg/L) Hg2+ in various water samples with a striking color transition from light orange to dark red upon complexation of probe with Hg2+. The solid-state sensors are Hg2+ ion selective, super-responsive, real-time applicable, and also reusable.

Glycine-modified organic polymer monolith featuring zwitterionic functionalities for hydrophilic capillary electrochromatography.

Allylglycine, a conventional amino acid derivative, possesses typical zwitterionic and hydrophilic functionalities deriving from the carboxyl and amino groups in its structure. A novel monolithic column poly(allylglycine-co-1, 3, 5-triacryloylhexahydro-1, 3, 5-triazine) (AGly-co-TAT) with powerful hydrophilic selectivity and obvious zwitterionic feature was synthesized successfully with the monomer allyglycine and the cross-linker 1, 3, 5-triacryloylhexahydro-1, 3, 5-triazine through in-situ copolymerization for capillary electrochromatography. The obtained monolithic column has good permeability. Due to the zwitterionic functional groups of allylglycine, the poly(AGly-co-TAT) monolithic column can generate a cathodic and anodic electroosmotic flow (EOF) by changing the mobile phase pH, which is beneficial to expand its application range. The separations of different series of polar analytes, thioureas, xanthines, phenols, peptides and acidic compounds are achieved on this hydrophilic monolithic column due to the powerful hydrophilic, electrostatic and hydrogen bond interactions. Using this monolithic column, hydrophilic separations are achieved even at a lower level of 50% organic solvent. The separation efficiency up to 1.41×105 N m-1 and 1.19×105 N m-1 is achieved for the separation of theophylline and phenol, respectively. For a real sample, cytochrome C digestion, the monolithic column shows good separation performance, which offers the potential application of the monolithic column on proteomics study.

Preparation of porous polymers based on high internal phase emulsion for enrichment of estrogens in urine.

In this work, graphene oxide-hybridized high internal emulsion polymers with crosslinking and open-cell structure was prepared and applied for separation and enrichment of estrogens. The prepared graphene oxide-hybridized high internal emulsion polymer monoliths had hydrophobicity, porosity and stability, which were just obtained by one step in-situ emulsion polymerization of 2-ethylhexyl acrylate, glycidyl methacrylate, and divinylbenzene after doping with graphene oxide. Benefit from the advantages of its unique character, the graphene oxide-hybridized high internal emulsion polymers monolith with low background pressure (85kPa) and high mechanical strength could be applied for efficient separation for trace estrogens in urine. Under the optimized condition, trace estrogens, including estrone, estradiol, and diethylstilbestrol in urine, were detected by high-performance liquid chromatography, all the sample preparation process were carried out in 15min, the recovery rate was ranged from 85.0 to 106.0% and the relative standard deviation was less than 4.

Structurally designed porous polymer monoliths as probe-anchoring templates as benign and fast responsive solid-state optical sensors for the sensing and recovery of copper ions

In this study, we report on the superior ion-capturing and sensing competence of a new breed of aqua-compatible solid-state ion-sensor using a structurally organized polymer monolith, for the ocular sensing of trace levels of divalent copper ions. The polymer monolithic template exhibits a single block framework with a uniform structural pattern and porous network that serves as an efficient host for the homogeneous probe anchoring, to constitute a renewable solid-state optical sensor. Here, a series of solid-state colorimetric Cu(II) sensors has been designed using three indigenously synthesized chelating probes (molecules) namely, 4-butyl-N-(2-(2,4-dinitrophenyl)hydrazine-1-carbonothioyl)benzamide (BNHCB), 2-(thiophen-2-ylmethylene)hydrazinen-1-carbothioamide (TMHCA), and 4-butylphenyl(diazenyl)-2-mercaptopyrimidine-4,6-diol (BDMPD). The polymer monoliths are characterized using various surface and structural analysis techniques such as HR-SEM, HR-TEM, XPS, XRD, FT-IR, EDAX, and BET surface area analysis. The fabricated solid-state sensors exhibit excellent selectivity and sensitivity for copper ions with unique color transitions that are reliable even at ultra-trace (ppb) levels. The impact of diverse sensing parameters such as solution pH, probe concentration, sensor quantity, target ion concentration, temperature, response kinetics, and matrix tolerances have been optimized. The fabricated sensor materials proffer maximum sensing efficiency in neutral pH conditions, with a limit of detection (LD) and quantification (LQ) values of 0.56 and 1.87 μg l−1, 0.30 and 1.0 μg l−1, and 0.12 and 0.42 μg l−1, for BNHCB-, BDMPD-, and TMHCA-anchored polymer sensors, respectively. The proposed reusable solid-state colorimetric sensors are environmentally benign, cost-effective and data reproducible, with superior analytical performance.

Magnetic monolithic polymers prepared from high internal phase emulsions and Fe3O4 triazole-functionalized nanoparticles for Pb2+, Cu2+ and Zn2+ removal

A series of magnetic interconnected microcellular poly(styrene-DVB) polymeric monoliths were prepared by the polymerization of high internal phase emulsion (HIPE) templates then used as adsorbents to remove Pb2+, Cu2+ and Zn2+ ions from wastewaters. Magnetic Fe3O4 nanoparticles functionalized with 1,2,3-triazole cycle (MNP-Trz) were used to stabilize the emulsions and to impart magnetic properties and additional chelating sites to the porous materials. Important variations in microstructure were achieved by adjusting the concentration of MNP-Trz nanoparticles. The effects of external adsorption conditions including pH, initial concentration and contact time on the adsorption properties were systematically investigated. It was demonstrated that the adsorption equilibrium can be rapidly reached within 25 min for Cu2+ and Zn2+ and 40 min for Pb2+ with high maximal adsorption capacities of 303.3, 149.2 and 135.9 mg.g−1 for Pb2+, Cu2+ and Zn2+ respectively at pH = 5.5 and T = 25 °C. The easy and versatile preparation and excellent performance make these magnetic porous polymers excellent candidates for metal remediation.

A micro-solid phase extraction device to prepare a molecularly imprinted porous monolith in a facile mode for fast protein separation.

A molecularly imprinted polymeric monolith was synthesized in an aqueous environment in 15min via UV-irradiation. The imprinted monolith was composed of hydroxyethyl methacrylate as monomer, dimethyl amino ethyl methacrylate as functional monomer, methylene bisacrylamide and piperazine diacrylamide as crosslinkers and human serum albumin as template molecule. The synthesis took place in a PDMS-based device (2.5cm long) yielding a micro-solid phase extraction column (3×5mm) with two built-in fingertight connectors for an infusion pump and fraction collector. The imprinted monolith displayed the characteristic features of a porous polymeric monolith, had dimethyl amino ethyl methacrylate and human serum albumin as functional groups within the monolith and showed high permeability (0.51×10-13m2). 85% of the imprinted cavities were readily available for rebinding of human serum albumin with an imprinting factor of 1.3. In comparison to a non-imprinted monolith, molecular imprinting increased human serum albumin adsorption by > 30%. Imprinted monolith displayed selectivity for human serum albumin over other competing proteins (human transferrin, ovalbumin and carbonic anhydrase) with similar or different isoelectric points and size. Human serum albumin was adsorbed (in dynamic mode) with > 98% selectivity from diluted human plasma using the imprinted monolith device. Device to device reproducibility and reusability of the device for 5 cycles showcase the imprinted monolith micro-device efficiency.

Monolithic Column Prepared with UiO-66-2COOH MOF as Monomer for Enrichment and Purification of Ursolic Acid in Plants by Online Solid-Phase Extraction

A method for preparing a metal–organic framework (MOF)–polymeric monolith was established by in situ radical polymerization with derivatized UiO-66-2COOH and N-isopropylacrylamide (NIPAAm) as co-monomers. It was worth noting that the obtained monolith possessed characteristics of relatively uniform porous structure and a high surface area (84.16 m2 g−1). The adsorption capacity of the monolith increased from 22.87 to 44.92 mg−1 due to the addition of MOF. The monolith was used as adsorbent and coupled with HPLC for the online purification and extraction of ursolic acid (UA) in medicinal plant. The limit of detection (LOD, S/N = 3) and the limit of quantification (LOQ, S/N = 10) were 0.17 μg mL−1 and 0.57 μg mL−1, respectively; the relative standard deviation (RSD) of intra-day and inter-day assays for five plant samples were 1.00–3.67% and 2.43–5.76%, respectively; a good accuracy was demonstrated by the recovery of 92.2–103.28%. The results indicated that the MOF–polymer monolith was feasible for the online enrichment and purification of UA in plant.

Development of an aptamer-functionalized capillary monolithic column for the highly-selective and highly-efficient recognition of patulin

Patulin is a type of mycotoxin that can compromise both food quality and human health, and its potential toxic effects on human health are concerning. Therefore, strict monitoring of patulin content in food systems is necessary. However, discrimination and quantification of this toxin are difficult because of its extremely low concentration at pg/g levels in food samples. A highly specific sample preparation method is, thus, vital for patulin analysis. Herein, we present an innovative approach for the facile and controllable preparation of an aptamer-functionalized capillary monolithic polymer hybrid for the determination of patulin in food samples with high specificity and high affinity by using the aptamer-functionalized monolithic capillary polymer hybrid as a sorbent for solid-phase microextraction (SPME) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The results confirmed that the developed SPME-UHPLC-MS/MS method was a sensitive and selective because of a low detection limit of 2.17 pmol/L and a linear range extending from 0.00811 to 8.11 nmol/L. Patulin was found to be present in apple juice samples (4.34 ng/kg). Furthermore, the recoveries were 85.4–106% with relative standard deviations (n = 5) of 4.1–7.3%. Thus, the highly selective method will facilitate the ultrasensitive detection of target molecules in diverse applications.

Organic solvent-free fabrication of mesoporous polymer monolith from miscible PLLA/PMMA blend

The fabrication of monoliths by environment-friendly methods without organic solvents remains a challenging task. In this study, we successfully produced mesoporous polymer monoliths by selective hydrolysis degradation of miscible poly(-L-lactic acid) (PLLA)/poly(methyl methacrylate) (PMMA) blends without any organic solvents. 50 to 90 wt% of PLLA blend ratios were tested. We found that freeze-dried was effective to prevent a shrinkage of monoliths. With increaser of PLLA weight fraction, porosity, mode pore diameter, and pore geometry could be controlled from 17 to 52%, 7.1–32 nm, and mainly cylindrical to spherical, respectively. Further, a comprehensive model based on volume balance and surface area equivalence successfully predicted mode pore size. The reported organic solvent-free fabrication of mesoporous polymer monoliths might enable tunable mesopore properties through only changing mechanical blending of miscible polymers.

Polystyrene‐Supported PPh3 in Monolithic Porous Material: Effect of Cross‐Linking Degree on Coordination Mode and Catalytic Activity in Pd‐Catalyzed C−C Cross‐Coupling of Aryl Chlorides

AbstractHybridization of porous synthetic polymer and sophisticated ligands play an important role in transition‐metal catalysis for chemical transformations at laboratory and industrial levels. A monolithic porous polymer, which is a single piece with continuous macropores, is desired for high permeability, fast mass transfer properties, high stability, and easy modification. Herein, we first develop a monolithic porous polystyrene containing three‐fold cross‐linked PPh3 (M‐PS‐TPP) for transition‐metal catalysis. The monolithic and macroporous structure of M‐PS‐TPP was fabricated via polymerization‐induced phase separation using porogenic solvent. Moreover, the M‐PS‐TPP was synthesized using different feed ratios of divinylbenzene (DVB) for site‐isolation and mono‐P‐ligating behavior of PPh3. 31P CP/MAS NMR analysis revealed that the different selectivity of M‐PS‐TPPs was obtained in formation of mono‐P‐ligation toward PdII. The macroporous properties and controlled mono‐P‐ligating behavior of M‐PS‐TPP facilitated the challenging Pd‐catalyzed Suzuki‐Miyaura cross‐coupling reaction of chloroarenes.

A 3D miniaturized solid-state chemiluminescence sensor based on ruthenium functionalized polymeric monolith for the detection of pharmaceutical drugs

For the first time, a 3D network of poly(methacrylic acid-co-ethylene dimethacrylate (poly(MAA-co-EDMA)) monolith is used as a solid support for a miniaturized solid-state chemiluminescence (CL) system. The positively charged Ru(bpy)32+ complex was electrostatically linked to the negatively charged monolith to form Ru(bpy)32+ -poly(MAA-co-EDMA). The Ru(bpy)32+ -poly(MAA-co-EDMA) was thoroughly studied using Fourier-transform infrared spectroscopy (FTIR), surface area measurement, isoelectric point, scanning electron microscopy (SEM), UV–Vis, fluorescence and microwave plasma-atomic emission spectrometer (MP-AES). The results showed the successful formation of the 3D structure and the linkage of Ru(bpy)32+ onto its surface. Surface area measurements showed a drastic decrease in the surface area of the monolith from 80.9 to 5.58 m2 g−1 upon the introduction of Ru(bpy)32+ due to its incorporation within the micropores of the monolith. The 3D miniaturized solid-state CL platform was optimized by studying the effect of the concentration of the oxidant, the concentration of H2SO4 and the flow rate using oxalate as a model analyte. The optimized platform was then used for the detection of oxalate and two pharmaceutical drugs, namely methapyrilene and imipramine, for clinical and forensic applications. Under optimal conditions, the calibration curves of both methapyrilene and imipramine pharmaceutical drugs are linear over the range from 5 to 50 pM, with limits of detection of 6.8 and 8.2 pM, respectively. The limits of quantification of methapyrilene and imipramine were 20.6 and 24.7 pM, respectively. The developed Ru(bpy)32+ -poly(MAA-co-EDMA) platform is disposable, cost-effective, highly sensitive and can be portable.

β-Cyclodextrin covalent organic framework–modified organic polymer monolith as a stationary phase for combined hydrophilic and hydrophobic aqueous capillary electrochromatographic separation of small molecules

Aβ-Cyclodextrin covalent organic framework (β-CD COF) was successfully prepared under ambienttemperature with a mild chemistry strategy from heptakis(6-amino-6-deoxy)-β-cyclodextrin and terephthalaldehyde. It was embedded into the poly[(glycidyl methacrylate)-co-(ethylene dimethacrylate)] [poly(GMA-co-EDMA)] monolith and served as the β-CD COF material-incorporated monolith. The synthetic materials were characterized by field emission scanning electron microscopy, energy-dispersive X-ray mapping analysis, transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, and N2 adsorption-desorption isotherm. The β-CD COF material-incorporated monolith achieved baseline separation in capillary electrochromatographic separationof three amides, three amino acids, three nucleosides, four aromatic acids, and three positional isomers (withresolutionvalues of three amides, 1.75 and 1.54; three amino acids, 5.24 and 1.75; three nucleosides, 2.56 and 1.77; four aromatic acids, 6.96, 2.74, and 1.64; three positional isomers, 1.61 and 1.50). In comparison with the original monolith, the β-CD COF material-incorporated monolith shows significantly enhanced resolution for mixed molecules. The effect ofpH and concentration of buffer and applied voltage were discussed in detail. The fabricated monolith showed good stability and reproducibility (relative standard deviation (RSD) < 6.9%). Molecular modeling illuminated the interactions between the small molecules and stationary phase, and provided a sufficient theoretical basis for experimental data. Graphical abstract Schematic presentation of the preparation of β-cyclodextrin covalent organic framework (β-CD COF) material-incorporated organic polymer monolith for separating the amides, amino acids, nucleosides, aromatic acids, and positional isomers. β-CD COF materials were synthesized and incorporated into the monolith as the stationary phase. Then, the incorporated monolith was applied in the capillary electrochromatography system for separating small molecules.

Online polymer monolith microextraction with in-situ derivatization for sensitive detection of endogenous brassinosteroids by LC-MS

An automatic and sensitive method which integrated polymer monolith microextraction and in-situ derivatization with liquid chromatography-mass spectrometry (PMME-ISD-LC-MS) was proposed for the quantification of endogenous brassinosteroids (BRs) in plant samples. In the described method, the anionic HIILIC monolithic column was modified with 2-methyl-4-phenylaminomethylphenylboronic acid (2-methyl-4-PAMBA) through ion exchange interaction and then used as a boronate affinity media to selectively capture, purify and derivatize BRs in crude extract through the reaction of the boronic acid group of 2-methyl-4-PAMBA and cis-diol on BRs. The BR derivatives were easily eluted by destroying the ion exchange interactions using the acidic eluting solvent, and then analyzed by LC-MS. The whole extraction and LC-MS analysis processes were automatically controlled which could be completed within 50 min. Under the optimized conditions, good linearities were obtained for six BRs with the correlation coefficients (R) ranging from 0.9953 to 0.9998. The limits of detection (LODs, S/N = 3) ranged from 0.10 to 1.29 pg mL−1. The recoveries were between 82.3% and 119.1% with the relative standard deviations (RSDs) ranging from 2.2% to 18.3%. Finally, the proposed method was applied for the quantification of endogenous BRs in various plant samples including different Oryza sativa L. cv. tissues (1.0 mg, fresh weight (FW)), Phaseolus vulgaris L. (1.0 mg FW), Vigna unguiculata (1.0 mg FW), Arabidopsis thaliana flower (1.3 mg FW).

Fabrication, characterization, and application of zeolitic imidazolate framework-8/acrylate monolithic polymer as a composite phase for stir bar sorptive extraction

Zeolitic imidazolate framework-8/polyacrylate monolithic (ZIF-8/PA) polymers have been prepared and optimized as a multifunctional material and used for application in stir bar sorptive extraction technique. The coating of ZIF-8/PA stir bar was characterized by FT-IR, XRD, and SEM techniques in terms of chemical structure, surface morphology, and composition homogeneity. Also, the extraction performance of prepared stir bars was obtained through the extraction of carvedilol and haloperidol from aqueous solutions. The intra- and inter-batch reproducibilities of stir bar fabrication were obtained 6.6 and 7.0%, respectively and the enrichment factors were in the range of 94–134. The optimum extraction and desorption conditions were achieved at sample pH value of 10, 90 min extraction time, 10 min desorption time, 40 °C desorption temperature and methanol as the desorption solvent for both analytes. At the optimum conditions the linear ranges were 3.8–500 µg L−1 for carvedilol and 10.7–500 µg L−1 for haloperidol with determination coefficients of over than 0.9935. The limits of detection of the method were 1.2 and 3.2 μg L−1 for carvedilol and haloperidol, respectively. The intra- and inter-day accuracies and precisions of the method were monitored at three concentration levels of each analyte. The recoveries were between 83 and 109%, and the relative standard deviations were less than 6%. The method is applicable for the determination of carvedilol and haloperidol in the lake and river water and human plasma samples with recoveries between 98 and 109% and relative standard deviation of less than 9%.

Innovations in Extractive Phases for In-Tube Solid-Phase Microextraction Coupled to Miniaturized Liquid Chromatography: A Critical Review.

Over the past years, a great effort has been devoted to the development of new sorbents that can be used to pack or to coat extractive capillaries for in-tube solid-phase microextraction (IT-SPME). Many of those efforts have been focused on the preparation of capillaries for miniaturized liquid chromatography (LC) due to the reduced availability of capillary columns with appropriate dimensions for this kind of system. Moreover, many of the extractive capillaries that have been used for IT-SPME so far are segments of open columns from the gas chromatography (GC) field, but the phase nature and dimensions are very limited. In particular, polar compounds barely interact with stationary GC phases. Capillary GC columns may also be unsuitable when highly selective extractions are needed. In this work, we provide an overview of the extractive capillaries that have been specifically developed for capillary LC (capLC) and nano LC (nanoLC) to enhance the overall performance of the IT-SPME, the chromatographic separation, and the detection. Different monolithic polymers, such as silica C18 and C8 polymers, molecularly imprinted polymers (MIPs), polymers functionalized with antibodies, and polymers reinforced with different types of carbon nanotubes, metal, and metal oxide nanoparticles (including magnetic nanoparticles), and restricted access materials (RAMs) will be presented and critically discussed.

Development of Macroporous Polymer Monolith Immobilizing L-Proline-Based Organocatalyst and Application to Flow Asymmetric Aldol Addition Reaction

Development of Macroporous Polymer Monolith Immobilizing L-Proline-Based Organocatalyst and Application to Flow Asymmetric Aldol Addition Reaction

Determination of Monoaromatic Hydrocarbons in Water Samples by Nano-Liquid Chromatography using a Composite Carbon Nanotubes- Lauryl Polymethacrylate Capillary Monolithic Column

Background: This work reports a green analytical method for the determination of organic environmental pollutants using nano-liquid chromatography with a self-made column for rapid, sensitive, inexpensive and efficient analysis of BTX pollutants in water. The applications of monolithic nanoscale columns for quantitative analysis of environmental real samples are very limited in the literature. Methods: A capillary column containing a composite of multi-walled carbon nanotubes incorporated into a lauryl methacrylate-co-ethylene dimethacrylate porous monolithic polymer was fabricated for the determination of BTX pollutants in real water samples. Results: Baseline separation was accomplished at 0.4 µL/min flow rate with UV-detection set at 208 nm. Under the optimum conditions, the calibration curves were validated over the range of 1.0-500 µg/L with R2 more than 0.9992. The detection limits of benzene, toluene, o-xylene and m/p-xylene were 0.25, 0.05, 0.075 and 0.05 µg/L, respectively. After a simple extraction process with a theoretical preconcentration factor equal to 200, the recovery values in Milli-Q, tap and sea water samples were found to be ranged from 84.85 to 97.84% with %RSD less than 7.5. Furthermore, we reported a comparison between our prepared composite column with a commercial C18 silica based column which is the most used in such analytical field. Each column demonstrated its advantages from different analytical aspects. Conclusion: The application of monolithic columns and nano-scale LC for routine analysis of environmental samples is very promising as the use of monolithic capillary columns offers several advantages over conventional scale particulate packed columns.

Fabrication of polymer monoliths within the confines of non-transparent 3D-printed polymer housings

In the last decade, 3D-printing has emerged as a promising enabling technology in the field of analytical chemistry. Fused-deposition modelling (FDM) is a popular, low-cost and widely accessible technique. In this study, RPLC separations are achieved by in-situ fabrication of porous polymer monoliths, directly within the 3D-printed channels. Thermal polymerization was employed for the fabrication of monolithic columns in optically non-transparent column housings, 3D-printed using two different polypropylene materials. Both acrylate-based and polystyrene-based monoliths were created. Two approaches were used for monolith fabrication, viz. (i) in standard polypropylene (PP) a two-step process was developed, with a radical initiated wall-modification step 2,2′-azobis(2-methylpropionitrile) (AIBN) as the initiator, followed by a polymerization step to generate the monolith; (ii) for glass-reinforced PP (GPP) a silanization step or wall modification preceded the polymerization reaction. The success of wall attachment and the morphology of the monoliths were studied using scanning electron microscopy (SEM), and the permeability of the columns was studied in flow experiments. In both types of housings polystyrene-divinylbenzene (PS-DVB) monoliths were successfully fabricated with good wall attachment. Within the glass-reinforced polypropylene (GPP) printed housing, SEM pictures showed a radially homogenous monolithic structure. The feasibility of performing liquid-chromatographic separations in 3D-printed channels was demonstrated.