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| 2. |
- Koivisto, Pernilla, et al.
(författare)
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Determination of the free concentration of ropivacaine in plasma by packed capillary liquid chromatography : A comparison of ultrafiltration and microdialysis as sample preparation methods
- 2001
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Ingår i: Journal of Microcolumn Separations. - : Wiley. - 1040-7685 .- 1520-667X. ; 13:5, s. 197-201
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Tidskriftsartikel (refereegranskat)abstract
- In this study, ultrafiltration and microdialysis have been compared as sample preparation methods to separate the free fraction of ropivacaine from the protein bound in 150 μL plasma. A liquid chromatographic system with packed capillary columns (0.2 mm internal diameter) was used to enhance sensitivity when analyzing the small sample volumes obtained after the ultrafiltration and the microdialysis. The microdialysis was performed with probes of our own construction, and to save analysis time, the microdialysis sampling was coupled on-line to the liquid chromatographic system. The reduction of back pressure in the microdialysis outlet tube and in the injector was found to be essential. The free fraction obtained with each method was equivalent: both gave a free fraction of 6%.
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| 3. |
- Nilsson, S, et al.
(författare)
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Evaluations of the stability of sheathless electrospray ionization mass spectrometry emitters using electrochemical techniques
- 2001
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 73:19, s. 4607-4616
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Tidskriftsartikel (refereegranskat)abstract
- The processes that cause the failure of sheathless electrospray ionization (ESI) emitters, based on different kinds of gold coatings on fused-silica capillaries, are described and explained. The methods chosen for this study include electrochemical methods, ICPMS analysis of the electrolytes used, SEM studies, and electrospray experiments. Generally, the failure occurs by loss of the conductive coating. It is shown that emitters with sputter-coated gold lose their coatings because of mechanical stress caused by the gas evolution accompanying water oxidation or reduction. Emitters with gold coatings on top of adhesion layers of chromium and nickel alloy withstand this mechanical stress and have excellent durability when operating as cathodes. When operating as anodes, the adhesion layer is electrochemically dissolved through the gold film, and the gold film then flakes off. It is shown that the conductive coating behaves as a cathode even in the positive electrospray mode when the magnitude of a superimposed reductive electrophoretic current exceeds that of the oxidative electrospray current. Fairy-dust coatings developed in our laboratory (see Barnidge, D. R., et al. Anal. Chem. 1999, 71, 4115-4118) by gluing gold dust onto the emitter, are unaffected by the mechanical stress due to gas evolution. When oxidized, the fairy-dust coatings show an increased surface roughness and decreased conductivities due to the formation of gold oxide. The resistance of this oxide layer is however negligible in comparison with that of the gas phase in ESI. Furthermore, since no flaking and only negligible electrochemical etching of gold was found, practically unlimited emitter lifetimes may be achieved with fairy-dust coatings.
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| 7. |
- Svedberg, M, et al.
(författare)
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Electrospray from a plastic chip
- 2001
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Ingår i: Micro Total Analysis Systems 2001, Monterey, USA. ; , s. 335-336
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Konferensbidrag (refereegranskat)
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