| 1. |
- Appelblad, Patrik, et al.
(författare)
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Determination of C-21 ketosteroids in serum using trifluoromethanesulfonic acid catalyzed precolumn dansylation and 1,1’-oxalyldiimidazole postcolumn peroxyoxalate chemiluminescence detection
- 1998
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Ingår i: Analytical Chemistry. - Washington : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 70:23, s. 5002-5009
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Tidskriftsartikel (refereegranskat)abstract
- A new procedure for the quantitation of C-21 ketosteroids using trifluoromethanesulfonic acid-catalyzed precolumn dansylation and coupled column liquid chromatographic separation, followed by postcolumn 1,1‘-oxalyldiimidazole peroxyoxalate chemiluminescence detection is presented. In the simultaneous optimization of chromatographic resolution and chemiluminescence intensity, a coupled column chromatographic system and a stopped-flow system were used. An eluent containing 20 mM phosphate buffer at pH 6.7 accomplished an efficient separation of 3α-hydroxy-5β-pregnan-20-one from a mixture containing 10 C-21 ketosteroids. Phosphate buffer also proved to be the most advantageous, among the six buffers tested, for sensitive detection. Experimental design and multivariate data analysis were used to characterize and optimize the postcolumn reaction chemistry in the chromatographic system. A valid full factorial design with excellent predictability showed that the flow rates for both 1,1‘-oxalyldiimidazole and hydrogen peroxide were the factors most strongly affecting the sensitivity of the system. The theoretical plate numbers were above 11 000 for all 10 dansylated ketosteroids. The 3σ detection limit estimated from 3α-hydroxy-5β-pregnan-20-one calibration curve data was 1.6 pmol (n = 4, 125 μL injected) and spiked serum containing 0−74 pmol of this compound showed overall recoveries of 73 ± 9% (n = 12). Quantitation of 3α-hydroxy-5β-pregnan-20-one was finally carried out on 45 serum samples and the results compared to those from a radioimmunoassay (RIA) method. The data acquired with the procedure described in this work compare well with the results from RIA, which confirms the reliability of the new analytical procedure.
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| 2. |
- Appelblad, Patrik, et al.
(författare)
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Fast hydrophilic interaction liquid chromatographic separations on bonded zwitterionic stationary phase
- 2008
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 31:9, s. 1529-1536
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Tidskriftsartikel (refereegranskat)abstract
- Separation science is an art of obtaining adequate resolution of the desired compounds in minimum time, and with minimum effort in terms of sample preparation and data evaluation. In LC, where selectivity is a main driving force for separation, the availability of different separation modes capable of operating at high flow rates is a way to make combined optimal use of selectivity, efficiency, and speed. The separation of polar and hydrophilic compounds is problematic in RP LC due to the poor retention. Hydrophilic interaction liquid chromatography (HILIC) is a more straightforward separation mode to address this problem. Herein, it is shown that separations in HILIC mode are equally efficient as for RP, providing a potential for very fast separations on short columns. This is not only facilitated by the low viscosity of the mobile phase compositions used, compared to typical RP eluents, but also due to higher column permeability. To exemplify this, baseline separations of uracil and cytosine are shown in less than 4 s and of Tamiflu® and its main metabolite in less than 40 s, both under isocratic conditions. HILIC must therefore be considered having potential for high throughput purposes, and being an attractive candidate as the second separation dimension in 2-D HPLC.
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| 3. |
- Appelblad, Patrik, et al.
(författare)
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Perfluorosulfonated Ionomer-Modified Polyethylene. A Material for Simultaneous Solid-Phase Enrichment and Enhanced Precolumn Dansylation of C-21 Ketosteroids in Human Serum
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:15, s. 3701-8
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Tidskriftsartikel (refereegranskat)abstract
- A new derivatization procedure has been developed where solid-phase catalysis is utilized to facilitate the formation of hydrazones in precolumn labeling of keto-containing compounds. This procedure has been implemented on a solid-phase enrichment and enhanced derivatization (SPEED) device, prepared from porous polyethylene that has been coated with Nafion and dansylhydrazine. The SPEED devices have been optimized using experimental design and characterized for dansylation of C-21 ketosteroids by multivariate data analysis, using progesterone as the model compound. The reaction temperature and the molar ratio between the steroid and the derivatization reagent were found to be the factors most strongly affecting the reaction. Faster reaction kinetics were achieved when the molar ratio between dansylhydrazine and the steroid was increased. Mass spectroscopic analysis showed that the four derivative peaks eluting when derivatized progesterone was separated on an octadecyl silica stationary phase were due to the syn and anti mono- and bis(hydrazones) formed in the reaction. Using optimal reaction conditions, the derivatives mainly constitute the syn and anti conformers of bis-derivatives. In contrast to solution-based acid catalysis, the SPEED device was remarkably insensitive to water in the reaction mixture. A sample volume of 400 L was found to be the maximum, enabling sample enrichment prior derivatization. Using optimal experimental conditions, picomole amounts of ketosteroids could be derivatized in 10 min at room temperature. Analysis of spiked serum samples containing 0.4-2.0 nmol of progesterone showed overall recoveries of 52-63%. The corresponding 3 detection limit was 1.3 pmol (n = 4, 100 L injected), as estimated from calibration curve data.
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| 4. |
- Appelblad, Patrik, et al.
(författare)
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Separation and detection of neuroactive steroids from biological matrices
- 2002
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Ingår i: Journal of Chromatography A. ; 955:2, s. 151-82
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Tidskriftsartikel (refereegranskat)abstract
- This review is based on a selection of research papers published mainly in the last decade and it describes various analytical aspects of separation and detection of neuroactive steroids in biological matrices.
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| 5. |
- Basu, Basudeb, et al.
(författare)
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Organic Polymeric Resins Embedded with Pd NPs : Newly Designed, Efficient and Chemoselective Catalyst for Reduction of Nitrobenzenes
- 2017
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Ingår i: Current Organocatalysis. - : Bentham Science Publishers. - 2213-3372 .- 2213-3380. ; 4:1, s. 48-61
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Tidskriftsartikel (refereegranskat)abstract
- Background: Organic polymer supported palladium nanoparticles (NPs) are important for use as heterogeneous catalyst in various organic reactions. This works describes Pd Nps immobilized on to polystyrene-based ion-exchange resin surface for use as catalyst in the reduction of nitrobenzenes. The heterogeneous catalyst was found useful for hydrogenation of nitro group under both catalytic transfer hydrogenation (CTH) as well as by using molecular hydrogen (H2).Methods: The catalyst was prepared from Amberlite IRA 900 Cl after rinsing with formic acid (10%) and subsequent treatment with Na2PdCl4 in DMF. The resulting Pd Nps immobilized resins was designated as VersaCat Pd and used for CTH of nitrobenzenes in the presence of H-donors (sodium formate, formic acid, hydrazine hydrate) and also for hydrogenation with H2 gas. The catalyst was characterized by FT-IR, MAS-NMR, SEM, TEM and XPS and surface morphologies were studied before and after the reaction.Results: Hydrogenations of nitrobenzenes under CTH using different H-source and direct use of H2 gas were achieved successfully with good to excellent yields. Reactions were performed under mild conditions and high degree of chemoselectivity was also observed. The catalyst was recyclable, used for six consecutive runs with appreciable conversions and showed higher activity (> 3 times) in terms of metalcontent than commercially available Pd/C (10%) in the hydrogenation of nitrobenzenes using H2 gas. The TEM images showed that Pd Nps are evenly distributed with size 50-200 mm on polymeric matrices and there was no significant changes observed after the first catalytic run. However, considerable rupture of the polymeric surface occurred after six runs, as seen from SEM studies.Conclusion: The present study establishes high catalytic efficiency and chemoselectivity of the newly developed organic polystyrene-based resin-soaked Pd NPs (VersaCat Pd) in the reduction of nitrobenzenes. Both CTH and hydrogenation using H2 gas were successfully done. Interestingly, hydrazine hydrate offered excellent control over chemoselectivity under CTH conditions and allowed clean conversion from nitro to amine, while keeping a chloro substitutent unaffected. Hydrogenation using molecular H2 gave maximum TOF. Easy preparation, high efficacy, TOF, chemoselectivity, and versatile applications are notable features for this heterogeneous palladium catalyst (VersaCat Pd). These features are often required in chemical industries.
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| 6. |
- Björnerbäck, Fredrik, 1984-
(författare)
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Sustainable porous organic materials : Synthesis, sorption properties and characterization
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The resources available to us humans, including metals, minerals, biomass, air, water, and anything else on the planet, are being used at an increasing rate. This anthropogenic use of resources both depletes the resources and has negative impacts on other resources, e.g. the biosphere. Thus, developing (more) sustainable chemical and industrial processes are of the utmost importance for the well-being of the creatures of Earth and for the long-term sustainability of human society.This thesis focuses on organic porous materials, and more specifically their synthesis and characterization. Porous materials are, for example, used in detergents, water treatment, bio gas upgrading, carbon dioxide capture, as catalysts, in sensors, and in various biological applications. The application of porous materials can contribute to the drive towards a more sustainable society. However, porous materials are typically not sustainable themselves. Thus, there is a need to develop more sustainable porous materials. The synthesis and characterization of three different groups of porous organic materials are described in this thesis.In pulp- and paper manufacturing, lignin is separated from desirable products and is typically combusted for heat. In one section of this thesis, lignin was used to produce bio-oil for potential use in fuels and chemicals. However, the bio-oil process produced a solid by-product. The by-product was used to synthesize and study activated carbons with very high porosities and magnetic properties, a combination of properties that may prove to be useful in applications.Sugar is known to produce solid and unwanted compounds through reactions with acids. It is shown here that it is possible to produce highly microporous humins, i.e. organic porous materials with a large amount of small pores, using sulphuric acid and a range of saccharides and bio-based polymers. This work supports that solid by-products in a wide range of biomass conversion processes can be of high value, both economically and as replacements for less sustainable alternatives.The biosphere contains vast amounts of molecules with aromatic structures. The last section of this thesis shows how such aromatic molecules can be used to produce highly porous materials through Friedel-Crafts type chemistry using sulfolane as a solvent and iron chloride as a catalyst. This synthesis strategy produces high-performance materials, improves upon the sustainability of traditional Friedel-Crafts chemistry, and makes use of typically underutilized and abundant bio-based molecules.
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| 7. |
- Bui, Nhat Thi Hong, 1984-
(författare)
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Polyhydroxyl and Polyphosphorylcholine functionalized Silica for Hydrophilic interaction liquid Chromatography- Synthesis, characterization and application
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the development of new stationary phases for use in hydrophilic interaction liquid chromatography using TRIS-based and phosphorylcholine typed monomers and porous silica particles as starting substrates. In this thesis, several ways of polymerizing highly hydrophilic monomers onto pore surfaces of silica supports are described, based on several “grafting from” schemes. “Controlled/living” radical polymerizations including atom transfer radical polymerization (ATRP) and iniferter-mediated polymerization in conjunction with conventional free radical polymerization are demonstrated to be successful tools for grafting different hydrophilic monomers (polyhydroxyl and phosphorylcholine [meth]acrylamide/acrylates) onto the silica surfaces. Reaction solvents are proven to play an essential role to achieve efficient graft polymerization of activated silica surfaces with these amphiphilic vinylic monomers, which is difficult because of their restricted access to the activated surface in solvents that can be used because of solubility constraints.Two tentacle TRIS-based polymer grafted silica, namely TRIS-WAX – TRIS functionality bonded to silica via a C–N–C imine bond and TRIS-Amide – TRIS bonded to silica via an amide bond, prove to be useful as stationary phases for hydrophilic interaction chromatography (HILIC).The TRIS-WAX exhibits a mixed mode hydrophilic partitioning and weak anion exchange (HILIC/WAX) retention mechanism while retention by hydrophilic partitioning is the dominant mechanism on the neutral TRIS-Amide phase which lacks weak anion exchange (WAX) properties. Interestingly, both these phases have selectivities that are radically different from most commercial HILIC stationary phases.Finally, a method is demonstrated for synthesizing a stratified (graft-copolymerized) silica material based on N,N′-methylenebisacrylamide and 2-methacryloyloxyethyl phosphorylcholine (MPC) using a “controlled/living” photoiniferter-mediated polymerization from the N,N-diethyldithiocarbamate iniferter moiety immobilized silica surfaces. This polymerization method proves to be successful for graft-blockcopolymerization of different highly hydrophilic monomers onto the activated surfaces of porous silica. In this way, silica surfaces are grafted with a cross-linked amide-based hydrogel, on top of which a tentacle zwitterionic phosphorylcholine-typed layer is synthesized. The resulted material proves to be useful for HILIC separations and possesses different selectivity for the tested organic acids compared to that of commercial ZIC-cHILIC stationary phase.
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| 8. |
- Bui, Nhat Thi Hong, et al.
(författare)
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Synthesis of poly(N-[tris(hydroxymethyl)methyl]acrylamide) functionalized porous silica for application in hydrophilic interaction chromatography
- 2012
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 35:23, s. 3257-3269
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Tidskriftsartikel (refereegranskat)abstract
- Porous silica coated by a highly hydrophilic and nonionic tentacle-type polymeric layer was synthesized by free radical "grafting from" polymerization of N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-2-propenamide (TRIS-acrylamide) in partly aqueous solutions. The radical initiator sites were incorporated on the silica surfaces via a two-step reaction comprising thionyl chloride activation and subsequent reaction with tert-butyl hydroperoxide. The surface-bound tert-butylperoxy groups were then used as thermally triggered initiators for graft polymerization of TRIS-acrylamide. The synthesized materials were characterized by diffusive reflectance Fourier transform infrared specotroscopy, X-ray photoelectron spectroscopy, and CHN elemental analysis. Photon correlation spectroscopy was used to determine changes in ζ-potentials resulting from grafting, (29) Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR) spectroscopy was used to assess the ratio of silanol to siloxane groups in the substrate and the grafted material, and the changes in surface area and mesopore distribution were determined by nitrogen cryosorption. Chromatographic evaluation in hydrophilic interaction chromatography (HILIC) mode showed that the materials were suitable for use as stationary phases, featuring good separation efficiency, a comparatively high retention, and a selectivity that differed from most commercially available HILIC phases. A comparison of this neutral phase with a previously reported N-(2-hydroxypropyl)-linked TRIS-type hydrophilic tentacle phase with weak anion exchange functionality revealed substantial differences in retention patterns.
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| 9. |
- Bui, Thai Q., 1989-
(författare)
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Development of nitrogen-containing materials for capture and catalytic conversion of carbon dioxide to value-added chemicals
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Anthropogenic carbon dioxide (CO2) emissions have become a critical environmental issue because a large amount of CO2 releasing into the atmosphere, particularly from the massive use of fossil fuels, is the major factor promoting the global warming and climate change. To mitigate the CO2 emissions, Carbon Capture, Utilization and Storage (CCUS) can be one of important solutions. Inspired by the CCUS approach, the aims of this thesis are to develop materials for CO2 capture (Papers I, II) and conversion of CO2 to value-added chemicals (Papers III, IV) such as dimethyl carbonate (DMC) and cyclic carbonates (CCs). The main idea is to focus on nitrogen-containing materials because basic nitrogen sites can increase the chemical affinity towards CO2, which is a weak Lewis acid gas.In practice, aqueous monoethanolamine (aq MEA) is widely used to capture CO2 from flue gases in CCUS projects. However, this solvent suffers from several major drawbacks such as high energy consumption for regeneration of MEA, degradation and evaporation. In Paper I, aq pentaethylenehexamine (PEHA) was proposed as an alternative solvent for chemical absorption of CO2. A comprehensive study was performed, including the influence of water content on CO2 capacity, chemical composition of absorption products, viscosities before and after absorption, regeneration of PEHA, correlation between CO2 capacity with Kamlet-Taft parameters, comparison with aq MEA. In Paper II, aq PEHA was further studied for CO2 capture from bio-syngas resulting from pilot-scale gasification of biomass to investigate the influence of other compositions on the capture performance. Additionally, this solvent was simultaneously used as a reagent for chemical pretreatment of biomass to investigate the influence of pretreatment on biomass gasification and CO2 capture.The conversion of captured CO2 to value-added chemicals gains increasing attentions in both academia and industry because CO2 represents a renewable, virtually inexhaustible, and nontoxic building block. In addition, this approach can provide economic incentives for CO2 capture facilities by selling their captured CO2 to other interested users or by benefiting from their own additional facilities using the CO2. In Paper III, 1,8-diazabicyclo[2.2.2]undec-7-ene (DBU) was used to capture and subsequent conversion of CO2 to DMC at ambient conditions. In Paper IV, mesoporous melamine-formaldehyde resins were prepared, characterized and studied as heterogeneous catalysts for synthesis of CCs from epoxides and CO2. These low-cost polymeric catalysts were reusable and demonstrated excellent performance in a flow reactor under industrially relevant conditions (120 °C, 13 bar, solvent-free/co-catalyst-free).Applications of ionic liquids (ILs) in capture and conversion of CO2 to organic carbonates were briefly reviewed in Paper V (mini review). The viscosity of ILs for CO2 capture and the mechanism involved in the CO2 binding were also discussed.In conclusion, this thesis will hopefully contribute to the sustainable development of society in the fields of reducing anthropogenic CO2 emissions and production of chemicals.
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| 10. |
- Bui Thi Hong, Nhat, et al.
(författare)
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Tris(hydroxymethyl)aminomethane-functionalized silica particles and their application for hydrophilic interaction chromatography
- 2010
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Ingår i: Journal of Separation Science. - : John Wiley & Sons. - 1615-9306 .- 1615-9314. ; 33:19, s. 2965-2976
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Tidskriftsartikel (refereegranskat)abstract
- A new method is presented for synthesizing a highly hydrophilic silica-based material for use in hydrophilic interaction chromatography. Porous silica particles used as a starting substrate were modified with 3-bromopropyl trichlorosilane and grafted with glycidyl methacrylate by controlled (“living”) atom transfer radical polymerization in order to introduce an oxirane-carrying reactive tentacle layer on the silica surface. The grafted material was thereafter subject to an oxirane ring opening reaction with tris(hydroxy-methyl)aminomethane in dimethylformamide to yield a polymer-bound equivalent of the well known and highly hydrophilic “TRIS” buffering substance. Chemical characterization was done by diffuse reflectance FT-IR, X-ray photoelectron spectroscopy, elemental analysis, and 1H NMR. Porosity and surface area examination was done with Brunauer–Emmett–Teller. Chromatographic application of the material was evaluated by separations of nucleic bases, small organic acids, and common nucleotides under mixed hydrophilic interaction chromatography and weak anion exchange conditions.
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