| 1. |
- Bökman, C.Fredrik, et al.
(author)
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A Setup for the Coupling of a Thin-Layer Electrochemical Flow Cell to Electrospray Mass Spectrometry
- 2004
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In: Analytical Chemistry. ; 76:7, s. 2017-2024
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Journal article (peer-reviewed)abstract
- A novel setup for the coupling of commercially available thin-layer cell to electrospray mass spectrometry (ESI-MS) which allows the elctrochemical reactions at the counter electrode to be straightforwardly separated from the flow into the mass spectrometer has been developed. In this way interferences from reaction products formed at the counter electrode can be minimized. This reduces the risk of changes in the mass spectra as a result of electrochemical reactions in the solution. The described setup also enables the working electrode to be positioned close to the electrospray (ESI) emitter without the need for a grounding point or a long transfer line between the electrochemical cell and the electrospray emitter. By decoupling the electrochemical reactions in the flow cell and those in the electrospray emitter, improved facilities for studies of electrochemical reactions are obtained through a better control of the potential of the working electrode. The setup has been used to study the oxidation of a drug (Olsalazine), which previously has been found to involve chemical follow-up reactions. It is also demonstrated that uncharged thiols can be detected in ESI-MS after spontaneous adsorption on a gold working electrode, followed by oxidative desorption to yield sulfinates or sulfonates. This adsorption and potential-controlled desorption has been used for the preconcentration of micromolar concentrations of 1-hexanethiol as well as for desalting of solutions containing micromolar concentrations of thiols. The results indicate that the present on-line coupling of an electrochemical cell to ESI-MS provides promising possibilities for sample preconcentration, matrix exchange (including desalting), and ionization of neutral compounds, such as thiols.
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| 2. |
- Sjöberg, Per J. R., et al.
(author)
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Factors influencing the determination of analyte ion surface partitioning coefficients in electrosprayed droplets
- 2001
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In: Journal of the American Society for Mass Spectrometry. - 1044-0305. ; 12:9, s. 1002-1010
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Journal article (peer-reviewed)abstract
- The observed response in mass spectrometry utilizing electrospray as a sample introduction technique can be affected by a number of factors. In this study a series of two-electrolyte systems was investigated and the mass spectrometric responses were modeled by the use of droplet surface partitioning coefficients and instrumental response factors according to a recently reported method (Sjo¨berg et al., Anal. Chem. 2001, 73, 23–28). The partitioning coefficient and the instrumental response factor were found to be affected by the chosen experimental conditions. Experimental parameters that were investigated include spray position relative to the orifice, spray potential, nebulizer and curtain gas flow rates, ionic strength, and organic content of the sprayed solution. The time history of the generated droplets turned out to be of importance to both the partitioning coefficients and the instrumental response factor. For example, a general increase in the surface partitioning coefficients for the tetrapentylammonium ion was initially observed when the spray was aiming closer to the sampling orifice. Furthermore, it was shown with a small amount of deuterium labeled electrolyte that the total ionic strength and not just the electrolyte concentration influence the instrumental response factor. (J Am Soc Mass Spectrom 2001, 12, 1002–1010)
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| 3. |
- Törnkvist, Anna, et al.
(author)
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Analysis of catecholamines and related substances using porous graphitic carbon as separation media in liquid chromatography-tandem mass spectrometry
- 2004
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In: Journal of Chromotography B. - : Elsevier BV. - 1570-0232. ; 801:2, s. 323-329
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Journal article (peer-reviewed)abstract
- Capillary porous graphitic carbon (PGC) columns have been utilized for separation of several catecholamines and related compounds (i.e. l-tyrosine, l-DOPA, 3-O-methyl-DOPA, dopamine, 3,4-dihydroxy-phenyl-acetic acid (DOPAC), homovanillic acid, noradrenaline, vanillomandelic acid and adrenaline) on-line with electrospray ionization tandem mass spectrometry (ESI–MS/MS). The use of a mobile phase without ion-pairing agents and with high content of organic modifier facilitated the coupling to the selective and sensitive mass spectrometric detection. Minimum detectable sample concentration (MDC sample) for noradrenaline, dopamine and l-tyrosine in a standard solution was estimated to 3, 10 and 30 nM, respectively (3 S/N corresponds to MDQ for l-tyrosine of approximately 8×10−14 mol). The developed strategy was applied for analysis of brain tissue, i.e. a substantia nigra (ns) sample.
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