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On-line coupling of microdialysis to packed capillary column liquid chromatography-tandem mass spectrometry demonstrated by measurement of free concentrations of ropivacaine and metabolite from spiked plasma samples
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry, Analytical Chemistry.
2002 (English)In: Journal of chromatography. B, ISSN 1570-0232, E-ISSN 1873-376X, Vol. 775, no 1, 79-87 p.Article in journal (Refereed) Published
Abstract [en]

An on-line coupling of microdialysis to a packed capillary column switching liquid chromatographic system (0.2 mm I.D.) and mass spectrometric detection was developed. The microdialysates were collected in the loop of the first of three valves, coupled in direct series. A deuterated internal standard was added on-line by the middle valve and the third valve operated both a pre-column, for desalting of the physiological buffer used in the sampling procedure, and a separation column. The on-line system was used to study free concentrations of ropivacaine and its metabolite (PPX) in human plasma samples. The analytes were detected by electrospray ionization in a tandem mass spectrometer operating in multiple reaction monitoring mode. The free fractions of ropivacaine (200 nM total concentration) and PPX (20 nM total concentration) in spiked plasma samples were 12±3 and 47±5% (±standard deviation for day-to-day variations, n=3), respectively.

Place, publisher, year, edition, pages
2002. Vol. 775, no 1, 79-87 p.
National Category
Analytical Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-93671DOI: 10.1016/S1570-0232(02)00280-5OAI: oai:DiVA.org:uu-93671DiVA: diva2:167218
Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Integrated Micro-Analytical Tools for Life Science
Open this publication in new window or tab >>Integrated Micro-Analytical Tools for Life Science
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Advances in life science require knowledge of active molecules in complex biological systems. These molecules are often only present for a certain time and at limited concentrations. Integrated micro-analytical tools for sampling, separation and mass spectrometric (MS) detection would meet these requests and are therefore continuously gaining interest. An on-line coupling of analytical functions provides shorter analysis time and less manual sample handling. In this thesis, improved compatibility of microdialysis sampling and multidimensional separations coupled to MS detection are developed and discussed.

Microdialysis was used in vitro for determination of the non-protein bound fraction of the drug ropivacaine. The sampling unit was coupled on-line to capillary column liquid chromatography (LC) followed by ultraviolet or MS detection. For MS detection, the system was extended with a desalting step and an addition of internal standard. A method for MS screening of microdialysates, collected in vivo, was also developed. The method involved sampling and measurements of the chemical pattern of molecules that generally are ignored in clinical investigations. Chemometric tools were used to extract the relevant information and to compare samples from stimulated and control tissues.

Complex samples often require separation in more than one dimension. On-line interfaces for sample transfer between LC and capillary electrophoresis (CE) were developed in soft poly(dimethylsiloxane) (PDMS). MS detection in the LC-CE system was optimised on frequent sampling of the CE peak or on high resolution in mass spectra using time-of-flight (TOF)MS or Fourier transform ion cyclotron resonance (FTICR)MS, respectively. Aspects on electrode positioning in the LC-CE interface led to development of an on-column CE electrode. A successful method for deactivation of the PDMS surface using a polyamine polymer was also developed. The systems were evaluated using peptides and proteins, molecules that are gaining increased attention in bioscience, and consequently also in chemical analysis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. 57 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 112
Keyword
Analytical chemistry, Microdialysis, Multidimensional separation, Liquid chromatography (LC), Capillary electrophoresis (CE), Electrospray ionisation (ESI), Mass spectrometry (MS), Microchip device, Free drug concentration, Screening of microdialysates, Pattern recognition, Analytisk kemi
National Category
Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-6049 (URN)91-554-6383-5 (ISBN)
Public defence
2005-11-25, B42, BMC, Husargatan 3, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-10-28 Created: 2005-10-28 Last updated: 2011-12-09Bibliographically approved

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Bergström, Sara K.

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