| 1. |
- Malmström, David, et al.
(författare)
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Continuous full filling capillary electrochromatography-electrospraying chromatographic nanoparticles
- 2011
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Ingår i: Electrophoresis. - : Wiley. - 0173-0835 .- 1522-2683. ; 32:2, s. 261-267
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Tidskriftsartikel (refereegranskat)abstract
- The influence of instrumental parameters affecting the ionization in continuous full filling capillary electrochromatography/electrospray ionization mass spectrometry (CFF-CEC/ESI-MS) was investigated. The investigated parameters were the BGE and sheath liquid ion strength and organic modifier content, the nebulizer gas pressure, and the concentration of nanoparticles in the BGE. It was found that the nebulizer pressure had the largest influence on the separation efficiency and apparent retention. It was shown that even the lowest pressure investigated was sufficient to guide the nanoparticle flow away from the mass spectrometer inlet. A nebulizer pressure of 5 psi was found to be optimal; increasing the pressure significantly decreased the separation efficiency due to the generation of a hydrodynamic flow. Generally, the ion strength of both the BGE and the sheath liquid were found to have very moderate effects on the separation of a homologous series of dialkyl phthalates, whereas the ionization efficiency was found to be unaffected by the nanoparticles and the separation efficiency was found to increase with increasing concentrations up to 3.8 mg/mL, whereafter it was observed to drop. The optimized method was linear over a wide concentration range and presented LOD and LOQ more than threefold lower than those previously reported using CFF-CEC/ESI-MS.
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| 2. |
- Nilsson, Christian, et al.
(författare)
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Nanoparticle-based continuous full filling capillary electrochromatography/electrospray ionization-mass spectrometry for separation of neutral compounds
- 2006
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 78:17, s. 6088-6095
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Tidskriftsartikel (refereegranskat)abstract
- Highly efficient reversed-phase capillary electrochromatography (CEC) separations (plate numbers up to 700 000/m), with electrospray ionization mass spectrometry detection were achieved utilizing novel dextran-coated polymer nanoparticles as a pseudostationary phase. A continuous full filling (CFF) technique in which nanoparticles are continuously introduced into the capillary was employed for separation of neutral analytes (dialkyl phthalates), utilizing an orthogonal electrospray interface to prevent nanoparticles from entering the mass spectrometer. CFF-CEC benefits from that an entirely fresh column is employed for every analysis, avoiding carryover effects associated with stationary-phase contamination. The highly efficient separations obtained were accomplished by optimizing the organic modifier concentration in the electrolyte and by using a high nanoparticle concentration (5 mg/mL), to improve interparticle mass transfer and gain sufficient retention. Nanoparticles, with an average diameter of 600 nm, were prepared by polymerization of methacrylic acid and trimethylolpropane trimethacrylate, which in turn were coated with dextran. These nanoparticles formed stable suspensions in electrolytes having broad ranges of polarities, enabling straightforward optimization of the reversed-phase conditions.
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| 3. |
- Santesson, Sabina, et al.
(författare)
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Airborne Single Cell Chemistry
- 2002
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Ingår i: European Biotechnology News. ; 1:1, s. 39-40
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 4. |
- Spégel, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Nanoparticle synthesis and evaluation
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 379-385
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Tidskriftsartikel (refereegranskat)abstract
- Reversed phase continuous full filling capillary electrochromatography with electrospray ionisation mass spectrometric detection was performed with highly sulphated poly [styrene-co-(lauryl methacrylate)-co-(divinylbenzene)] nanoparticles. The nanoparticles that contained a hydrophobic core and a hydrophilic surface were prepared in a one step synthesis using soap free emulsion polymerisation. By changing the concentration of monomers, the polymerisation temperature, and the polarity of the dispersive phase, the size of the nanoparticles could be controlled. With the optimised conditions, nanoparticles with an average size of 157 nm were obtained. These nanoparticles were dispersed in the background electrolyte and used for reversed phase continuous full filling. An orthogonal electrospray ionisation interface was used to separate the eluting nanoparticles from the eluting analytes prior to mass spectrometry detection. Compared to previous studies on reversed phase continuous full filling, the retention, the separation efficiency, and the resolution of a homologous series of dialkyl phthalates were greatly improved.
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| 5. |
- Viberg, Peter, et al.
(författare)
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Continuous full filling capillary electrochromatography: Chromatographic performance and reproducibility
- 2007
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673. ; 1154:1-2, s. 386-389
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Tidskriftsartikel (refereegranskat)abstract
- Continuous full filling capillary electrochromatography with nanoparticles as pseudostationary phase interfaced with electrospray ionisation mass spectrometric detection was used for reversed phase separations with very high separation efficiency. Several batches of nanoparticles were synthesised and their electrochromatographic performance were evaluated. Different parameters, such as repeatability, reproducibility, limit of detection, and peak asymmetry, were investigated yielding excellent results. The stability of the system over wide pH ranges and over time was found to be excellent. Very high separation efficiencies with over 1.1 million theoretical plates per metre were obtained. The limit of detection for the investigated dialkyl phthalates was approximately 1.0 mu mol L-1, corresponding to 3-5 fmol injected. After preparation, nanoparticle suspensions could be used without further treatment for at least an entire working day with maintained chromatographic qualities. (c) 2007 Elsevier B.V. All rights reserved.
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| 6. |
- Viberg, Peter, et al.
(författare)
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Nanoparticles as pseudo stationary phase in CEC/ESI-MS
- 2002
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Ingår i: Proceedings 50th ASMS Conference on Mass Spectrmetry and Allied Topics. ; , s. 905-906
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Konferensbidrag (refereegranskat)abstract
- A technique which uses polymer nanoparticles as interaction phase in capillary electrochromatography (CEC)-ESI-MS was described. A continuous full filling technique in which nanoparticles were suspended in the entire electrolyte volume as well as conventional partial filling technique were presented. The results verified that polymer nanoparticles suspended in electrolyte can be used as pseudo stationary phase in CEC with ESI-MS detection using continuous full filling and partial filling techniques. The sample molecules were separated from the nanoparticles in the orthogonal ESI-interface and MS-detection was performed despite the continuous flow of nanoparticles into the interface.
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| 7. |
- Viberg, Peter, et al.
(författare)
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Nanoparticles as pseudostationary phase in capillary electrochrornatography/ESI-MS
- 2002
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 74:18, s. 4595-4601
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique that uses polymer nanoparticles as pseudostationary phase in capillary electrochromatography with electrospray ionization mass spectrometry detection is described. A continuous full filling technique in which the nanoparticles were suspended in the entire electrolyte volume as well as a conventional partial filling technique is presented. No nanoparticles entered the mass spectrometer, which was fitted with an orthogonal electrospray interface, despite the continuous flow of nanoparticles into the interface. Nanoparticles (average diameter 160 nm) were prepared from methacrylic acid, methyl methacrylate, and trimethylolpropane trimethacrylate by utilizing a precipitation polymerization technique. Salbutamol, nortriptyline, and diphenhydramine were used as analytes. The interaction between analytes and nanoparticles was found to be predominantly ionic.
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| 8. |
- Viberg, Peter, et al.
(författare)
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Reversed phase continuous full filling CEC-ESI-MS
- 2007
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Ingår i: Chromatographia. - : Springer Science and Business Media LLC. - 0009-5893 .- 1612-1112. ; 65:5-6, s. 291-297
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Tidskriftsartikel (refereegranskat)abstract
- Nanoparticles were used as a pseudostationary phase in capillary electrochromatography (CEC) electrospray ionisation-mass spectrometry (ESI-MS) for separation of both neutral analytes by a reversed phase mechanism, as well as for cationic analytes by a cation exchange mechanism. Nanoparticles suspended in electrolyte, were injected as a plug prior to the sample using a partial filling technique (PF), or used as electrolyte in a continuous full filling (CFF) technique. An orthogonal ESI probe was used to hinder the nanoparticles from entering the mass spectrometer and to allow detection of analytes co-eluting with concentrated nanoparticle slurries. Two types of nanoparticles were synthesised and used, both of them having a hydrophobic core and a hydrophilic surface. The hydrophobic core gave the nanoparticles reversed phase properties and the hydrophilic surface promoted the formation of stable slurries of nanoparticles in electrolytes with a low concentration of organic modifier. The surface of one of the nanoparticle types was covered with sulphate groups that, besides from enhancing slurry stability and thus enabling reversed phase CEC, also enabled ion exchange CEC. Both nanoparticle types showed reproducible and interpretable retention properties.
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| 9. |
- Holdfeldt, Peter, 1976, et al.
(författare)
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A Dynamic Programming Inspired Method for Boundary Detection in Ultrasound Image Sequences with Application to Brachial Artery Flow-Mediated Dilation (FMD) Studies
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper describes a new method for boundary detection in ultrasound image sequences with specific application to brachial artery flow-mediated dilation (FMD) studies. The method represents an extension to conventional two-dimensional dynamic programming to be applied in a three-dimensional (spatio-temporal) context. A total of 42 digital image sequences, each of which contained 240 frames, were analyzed. The majority (34) of these sequences were analyzed successfully, and a few (8) partly successful. Following automated boundary detection, vessel diameter extrema (minima and maxima) could easily be computed and used for FMD calculations. It was concluded that the new method, although optimality when moving from two to three dimensions cannot be guaranteed, outperforms conventional dynamic programming.
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| 10. |
- Holdfeldt, Peter, 1976, et al.
(författare)
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A New Method Based on Dynamic Programming for Boundary Detection in Ultrasound Image Sequences
- 2008
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Ingår i: Engineering in Medicine and Biology Society, 2008. EMBS 2008. 30th Annual International Conference of the IEEE. EMBC 2008, August 20-24, Vancouver, Canada. - 9781424418145 ; , s. 3072-3074
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Konferensbidrag (refereegranskat)abstract
- Dynamic programming has previously been used when measuring Lumen Diameter (LD) and Intima-Media Thickness (IMT) in single frame ultrasound carotid artery images [1]. An extension to multiframe detection of that procedure is proposed in this paper. Our new method transforms a three dimensional problem into multiple two dimensional problems that can again be solved by dynamic programming. First, several “candidate boundaries” are detected in each image. Then, one boundary from each image in the sequence is selected in such a way that the sequence of boundaries is optimal among the considered possibilities. A model of the movements of the boundaries is used in the second step. Our proposed method shows promising performance on both synthetic and real ultrasound data.
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