Direct injection of plasma samples into restricted-access media precolumns for drug analysis in column-switching systems
1997 (English)Doctoral thesis, comprehensive summary (Other academic)
This thesis focuses on the theoretical and practical aspects of using column-switching systems for direct injection of plasma samples to assay drugs at ng/ml levels. The systems utilized a restricted-access media (RAM) precolumn for the sample clean-up and trace enrichment. The separation of analytes of interest was accomplished on a reversed-phase analytical column via a switching device in the back-flush mode.
Retention principles for the functional permission of direct injection of biological samples on RAMs were proposed. In the long course of plasma injections, RAM packings behaved distinctly different from conventional reversed-phase materials. Changes of retention, peak performance and column resistance after the injection of 10-20 ml of plasma were mainly resulted from the blockage of sealings or the adsorption of proteins on the hydrophilic layer of the packings.
The clean-up effect, the stability of the system and the choice of UV wavelength depended on the character of the RAM packings. However, the composition of the mobile phase serving for the RAM columns could affect the plasma elution profile, the recovery of plasma matrix and column lifetime.
Based on the developed systems, a detection limit of 10 ng/ml was obtained for the determination of weakly UV absorbing local anaesthetics with UV at 210 nm in conjunction with large volumes of plasma injection (500 _l). Analysis of methotrexate and its main metabolite in plasma was achieved with ion-pair conditions using on-line post-column photochemical reaction and fluorimetric detection. The method gave a limit of quantitation of methotrexate at 3.6 ng/ml.
Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 1997. , 40 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 0282-7484 ; 163
Research subject Analytical Pharmaceutical Chemistry
IdentifiersURN: urn:nbn:se:uu:diva-839ISBN: 91-554-3989-6OAI: oai:DiVA.org:uu-839DiVA: diva2:171221
1997-05-21, Lecture hall, B42, Biomedical Center, Uppsala University, Uppsala, 10:15