Novel Solid Phase Extraction and Mass Spectrometry Approaches to Multicomponent Analyses in Complex Matrices

Analysis of compounds present in complex matrices is always a challenge, which can be partly overcome by applying various sample preparation techniques prior to detection. Ideally, the extraction techniques should be as selective as possible, to minimize the concentration of interfering substances. In addition, results can be improved by efficient chromatographic separation of the sample components. The elimination of interfering substances is especially important when utilizing mass spectrometry (MS) as a detection technique since they influence the ionization yields. It is also important to optimize ionization methods in order to minimize detection limits. In the work this thesis is based upon, selective solid phase extraction (SPE) materials, a restricted access material (RAM) and graphitized carbon black (GCB) were employed for clean-up and/or pre-concentration of analytes in plasma, urine and agricultural drainage water prior to liquid chromatography/mass spectrometry (LC/MS). Two SPE formats, in which GCB was incorporated in μ-traps and disks, were developed for cleaning up small and large volume samples, respectively. In addition, techniques based on use of sub-2 μm C18 particles at elevated temperatures and a linear ion trap (LIT) mass spectrometer were developed to improve the efficiency of LC separation and sensitivity of detection of 6-formylindolo[3,2-b]carbazole (FICZ) metabolites in human urine. It was also found that GCB can serve not only as a SPE sorbent, but also as a valuable surface for surface-assisted laser desorption ionization (SALDI) of small molecules. The dual functionality of GCB was utilized in a combined screening-identification/quantification procedure for fast elimination of negative samples. This may be particularly useful when processing large numbers of samples. SALDI analyses of small molecules was further investigated and improved by employing two kinds of new surfaces: oxidized GCB nanoparticles and silicon nitride. 5 List of publications List of publications This thesis is based upon the following publications, which are referred to in the text by the corresponding Roman numerals. For convenience, the studies described in Papers I-VI are referred to as Studies I-VI, respectively. I Feasibility of an On-Line Restricted Access Material/Liquid Chromatography/Tandem Mass Spectrometry Method in the Rapid and Sensitive Determination of Organophosphorus Triesters in Human Blood Plasma Nahid Amini, Carlo Crescenzi Journal of Chromatography B 2003, 795: 245-256 II μ-Trap for the SALDI-MS Screening of Organic Compounds Prior to LC/MS Analysis Mohammadreza Shariatgorji, Nahid Amini, Gunnar Thorsen, Carlo Crescenzi, Leopold L. Ilag Analytical Chemistry 2008, 80: 5515-5523 III Screening and Quantification of Pesticides in Water Using a Dual-Function Graphitized Carbon Black Disk Nahid Amini, Mohammadreza Shariatgorji, Carlo Crescenzi, Gunnar Thorsen Analytical Chemistry 2010, 82: 290-296 IV The Suggested Physiologic Aryl Hydrocarbon Receptor Activator and Cytochrome P4501 Substrate 6-Formylindolo[3,2-b]carbazole is Present in Humans Emma Wincent, Nahid Amini, Sandra Luecke, Hansruedi Glatt, Jan Bergman, Carlo Crescenzi, Agneta Rannug, Ulf Rannug Journal of Biological Chemistry 2009, 284:2690-2696 6 List of publications V SALDI-MS Signal Enhancement Using Oxidized Graphitized Carbon Black Nanoparticles Nahid Amini, Mohammadreza Shariatgorji, Gunnar Thorsen Journal of the American Society for Mass Spectrometry 2009, 20:1207-1213 VI Silicon Nitride Nanoparticles for Surface-Assisted Laser Desorption/Ionization of Small Molecules Mohammadreza Shariatgorji, Nahid Amini, Leopold L. Ilag Journal of Nanoparticle Research 2009, 11:1509-1512 The contributions of the author of this thesis to these studies were as follows: Paper I: involved in developing the idea, responsible for all experiments and writing the major part of the paper. Papers II, III and V: involved in developing the idea, responsible for all experiments and writing the major part of the papers (all equal contributions with the first/second author). Paper IV: responsible for the LC/MS parts of the study: idea, experiments and writing. Paper VI: responsible partly for developing the idea, experiments and writing of the paper. The author also contributed to the following papers, but they are not included in the thesis. Matrix-Less Laser Desorption/Ionisation Mass Spectrometry of Polyphenols in Red Wine Zdeněk Spáčil, Mohammadreza Shariatgorji, Nahid Amini, Petr Solich, Leopold L. Ilag Rapid Communications in Mass Spectrometry 2009,