| 1. |
- Hemström, Petrus, et al.
(författare)
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Alternative organic solvents for HILIC separation of cisplatin species with on-line ICP-MS detection
- 2008
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Ingår i: Journal of Separation Science. - : John Wiley & Sons. - 1615-9306 .- 1615-9314. ; 31:4, s. 599-603
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Tidskriftsartikel (refereegranskat)abstract
- Several low volatile organic solvents were evaluated as organic modifiers in eluents for HILIC separations of cisplatin species to optimize the on-line coupling of HILIC to inductively coupled plasma MS (ICP-MS). The aim was to identify a solvent giving low solvent vapor loading of the ICP, to maximize analyte sensitivity and minimize carbon depositions on instrumental parts, while retaining chromatographic performance. The best overall performance of the HILIC-ICP-MS system for the analysis of cisplatin was achieved using 1,4-dioxane as eluent, yielding high retention and an HILIC type retention mechanism, at the expense of a 50% drop in column efficiency due to the higher viscosity of 1,4-dioxane compared to the more commonly used HILIC solvent ACN. Using 1,4-dioxane as solvent in HILIC provides the best compromise between carbon deposition and separation efficiency among a series of high-boiling water-miscible solvents tested.
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| 2. |
- Hemström, Petrus, et al.
(författare)
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Atom-transfer radical graft polymerization initiated directly from silica applied to functionalization of stationary phases for high-performance liquid chromatography in the hydrophilic interaction chromatography mode.
- 2006
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 78:20, s. 7098-7103
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Tidskriftsartikel (refereegranskat)abstract
- Initiation of atom-transfer radical polymerization of a number of monomers (styrene, methyl acrylate, 3-[N,N-dimethyl-N-(methacryloyloxyethyl)ammonium] propanesulfonate, butyl methacrylate, 2,3-epoxypropyl methacrylate) directly from chlorinated porous silica particles has been performed. The grafting has been confirmed and evaluated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. This initiation technique results in a hydrolytically stable initial Si-C bond, tethering the polymer to the silica substrate. The resulting grafted particles have been used as separation materials for both reversed-phase and hydrophilic interaction chromatography.
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| 3. |
- Hemström, Petrus, et al.
(författare)
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Hydrophilic interaction chromatography
- 2006
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29, s. 1784-1821
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Tidskriftsartikel (refereegranskat)abstract
- Separation of polar compounds on polar stationary phases with partly aqueous eluents is by no means a new separation mode in LC. The first HPLC applications were published more than 30 years ago, and were for a long time mostly confined to carbohydrate analysis. In the early 1990s new phases started to emerge, and the practice was given a name, hydrophilic interaction chromatography (HILIC). Although the use of this separation mode has been relatively limited, we have seen a sudden increase in popularity over the last few years, promoted by the need to analyze polar compounds in increasingly complex mixtures. Another reason for the increase in popularity is the widespread use of MS coupled to LC. The partly aqueous eluents high in ACN with a limited need of adding salt is almost ideal for ESI. The applications now encompass most categories of polar compounds, charged as well as uncharged, although HILIC is particularly well suited for solutes lacking charge where coulombic interactions cannot be used to mediate retention. The review attempts to summarize the ongoing discussion on the separation mechanism and gives an overview of the stationary phases used and the applications addressed with this separation mode in LC.
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| 4. |
- Hemström, Petrus, 1968-
(författare)
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Hydrophilic Separation Materials for Liquid Chromatography
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main focus of this thesis is on hydrophilic interaction chromatography (HILIC) and the preparation of stationary phases for HILIC. The mechanism of HILIC is also discussed; a large part of the discussion has been adapted from a review written by me and professor Irgum for the Journal of Separation Science (ref 34). By reevaluating the literature we have revealed that the notion of HILIC as simply partitioning chromatography needed modification. However, our interest in the HILIC mechanism was mainly inspired by the need to understand how to construct the optimal HILIC stationary phase. The ultimate stationary phase for HILIC is still not found. My theory is that a non-charged stationary phase capable of retaining a full hydration layer even at extreme acetonitrile (> 85%) concentrations should give a HILIC stationary phase with a more pure partitioning retention behavior similar to that of a swollen C18 reversed phase. The preparation of a sorbitol methacrylate grafted silica stationary phase is one of our attempts at producing such a stationary phase. The preparation of such a grafted silica has been performed, but with huge difficulty and this work is still far from producing a column of commercial quality and reprodicibility. This thesis also discusses a new method for the initiation of atom transfer radical polymerization from chlorinated silica. This new grafting scheme theoretically results in a silica particle grafted with equally long polymer chains, anchored to the silica carrier by a hydrolytically stable silicon-carbon bond. The hydrolytic stability is especially important for HILIC stationary phases due to the high water concentration at the surface.
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| 5. |
- Hemström, Petrus, et al.
(författare)
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Polymer-based monolithic microcolumns for hydrophobic interaction chromatography of proteins.
- 2006
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 29:1, s. 25-32
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Tidskriftsartikel (refereegranskat)abstract
- Monolithic capillary columns for hydrophobic interaction chromatography (HIC) have been prepared by thermally initiated, single-step in situ polymerization of mixtures of monovinyl monomers including butyl methacrylate and/or 2-hydroxyethyl methacrylate, with a divinyl crosslinker glycerol dimethacrylate or 1,4-butanediol dimethacrylate using two different porogen systems. Two porogenic solvent mixtures were used; one "hydrophilic", consisting of water, butanediol, and propanol, and one "hydrophobic," comprising dodecanol and cyclohexanol. The porous structures of the monoliths were characterized and their performance was demonstrated with a separation of a mixture of myoglobin, ribonuclease A, and lysozyme under conditions typical of HIC.
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| 6. |
- Nygren, Yvonne, 1965-, et al.
(författare)
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Hydrophilic interaction liquid chromatography (HILIC) coupled to inductively coupled plasma mass spectrometry (ICPMS) utilizing a mobile phase with a low-volatile organic modifier for the determination of cisplatin, and its monohydrolyzed metabolite
- 2008
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Ingår i: Journal of Analytical Atomic Spectrometry. - : Royal Society of Chemistry. - 0267-9477 .- 1364-5544. ; 23:7, s. 948-954
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Tidskriftsartikel (refereegranskat)abstract
- This study demonstrates the on-line coupling of hydrophilic interaction liquid chromatography (HILIC) to inductively coupled plasma mass spectrometry (ICPMS). A low volatile organic solvent, dimethylformamide (DMF), was used as organic modifier of the mobile phase to minimize the solvent loading of the ICP and thereby improve analyte sensitivity and method robustness. The concept was illustrated by the selective determination of cisplatin (cis-DDP), and its mono-hydrolyzed metabolite (MH-DDP). Species were separated on a 2.1 × 150 mm ZIC-HILIC column and detected on-line by selective platinum (m/z 194 and 195) monitoring, giving a detection limit of 2 pg Pt (0.2 ng ml-1). Compared to the use of the conventional solvent acetonitrile (AcN), with DMF, cis-DDP sensitivity was enhanced as much as 36 times and no addition of oxygen to the plasma was needed to avoid carbon depositions on instrumental parts. Furthermore, several non-identified platinum containing compounds were observed when using AcN as a result of unwanted reactions between this solvent and the analytes. No such species were observed when DMF was used. The molecular structures of eluting compounds were verified by electrospray ionization mass spectrometry. Combined with a simple sample treatment protocol, the HILIC-ICPMS system allowed determination of free intracellular cis-DDP in in-vitro grown T289 human malignant melanoma cells up to 60 min after exposure to 50 g ml-1 cis-DDP for 1 h. This work shows that HILIC-ICPMS is a potent hyphenated technique for the analysis of hydrophilic metal compounds and that the use of chromatographic mobile phases with low-volatile organic solvents may be a generic approach to improve analyte sensitivity and system robustness of HPLC-ICPMS when mobile phases with high amount of organic solvent are used.
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| 7. |
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| 8. |
- Persson, Jonas, et al.
(författare)
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Preparation of a sorbitol methacrylate grafted silica as stationary phase for hydrophilic interaction chromatography
- 2008
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Ingår i: Journal of Separation Science. - : Wiley. - 1615-9306 .- 1615-9314. ; 31:9, s. 1504-1510
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Tidskriftsartikel (refereegranskat)abstract
- A new highly hydrophilic stationary phase based on graft polymerization of sorbitol methacrylate from the surface of Kromasil silica particles is described. Polymerization was initiated by thermal cleavage of tert-butyl hydroperoxide covalently attached to the silica particle surface. Due to the highly amphiphilic properties of the monomer, an extensive search was needed to find solvent conditions that enabled surface-initiated polymerization. This was finally solved by using a mixture of solvents that only partially dissolved the monomer. The graft polymerization was confirmed by Fourier transform infrared spectroscopy and elemental analysis. The resulting stationary phase was evaluated by HPLC and exhibited a selectivity markedly different from that of commercially available columns and of neat silica.
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