Abstract Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a powerful tool for the analysis of biomolecules such as peptides and proteins and soft ionization technique using the organic matrix. Because of the high concentration of the organic matrix produces high background signals in the low mass range, nanopatticles have been intensively applied in the surface-assisted Laser desorption/ionization-mass spectrometry (SALDI-MS) to reduce the background interferences in the MALDI.-MS. This thesis includes two projects. The first project applied the copper oxide nanorods, which absorbs 337 nm UV laser energy and has the large area, as the matrix for SALDI-TOF MS to detect four large antibiotics, peptides and proteins. The optimized conditions of the four antibiotic drugs were: 1000 £gM of copper oxide nanorods and incubation for 30 minutes to get the best signals. The LODs of the Lasalocid, Monensin, Salinomycin and Narasin are 200 nM, 25 nM, 50 nM and 50 nM, respectively. In addition, in this project, the CuO nanorods also can be mixed with glycerol to enhance the detection sensitivity for peptides and proteins. The second project presents the zinc selenium quantum dots (ZnSe QDs) modified with 3-mercaptopropionic acid (3-MPA) as the matrix and affinity probes in the SALDI-TOF MS. It strengthens the interaction between the gramicidin and zinc selenium quantum dots by electric interaction in the pH 6 phosphate buffer solution according to the pI value of the gramicidin and the pKa of. 3-mercaptopropionic acid. The best sensitivity of the gramicidin can be obtained under the optimized conditions: 50 £gM of zinc selenium quantum dots, 30 minutes incubation time and pH 6 of phosphate buffer solution. The LOD of the gramicidin is 0.08 £gM. This approach also can be successfully applied in the SALDI-TOF MS to enhance the sensitivity of peptides and proteins.

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The thesis is divided into four sections. 1. Sample-first preparation: A method for surface-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of cyclic oligosaccharides¡GIn this work, we report the application of a sample first preparation method for the analysis of cyclic oligosaccharides when using bare AuNPs as the assisted matrix. In the sample first method, the analyte is deposited first and then followed by the bare AuNPs. The cyclic oligosaccharides, including £\-, £]-, and£^-cycodextrin (CD), are difficult to ionize by MALDI-MS, but they could be cationized very efficiently using bare AuNPs as matrixes in combination with a sample first preparation method. The sample first method not only provides high sensitivity for the measurement of neutral carbohydrate but also improves the spot homogeneity. This practical method was further validated by the analyses of biological samples, including neutral carbohydrate, neutral steroid, aminothiols, and peptides. 2. Gold nanoparticles as assisted matrix for detecting small biomolecules from high salt solutions through laser desorption/ionization mass spectrometry¡GThe neutral steroid and carbohydrates, which are difficult to be ionized by using MALDI, but cationized very efficiently by SALDI coupled with the sample first preparation method even if they are dissolved in a high-concentration NaCl solution. Under identical conditions, this practical method was further validated by the analysis of indolamines and peptides. It has also been utilized to analyze the small biomolecules in urine samples. 3. Phosphate-modified TiO2 nanoparticles for selective detection of dopamine, levodopa, adrenaline, and catechol based on fluorescence quenching¡GIn contrast to these studies, we report a simple approach for the selective detection of DA, L-DOPA, and adrenaline by phosphate-modified TiO2 (P-TiO2) NPs in the presence of fluorescein. After the binding of DA, the P-TiO2 NPs become neutral and even positively charged. The adsorption of fluorescein on the particles results in the quenching of fluorescein by TiO2-DA complexes, which have strong absorption at 428 nm. By monitoring the decreases in fluorescence at 520 nm for fluorescein, we calculated the limits of detection (LODs) for DA, L-DOPA, and adrenaline at a signal-to-noise (S/N) ratio of 3, which were 33.5, 81.8, and 20.3 nM, respectively. The results imply that the proposed methods have great potential for use in the selective analysis of catecholamines in biological samples and clinical applications. 4. Sodium hydroxide as pretreatment and fluorosurfactant-capped gold nanoparticles as sensor for the highly selective detection of cysteine¡G Under acidic conditions, fluorosurfactant (FSN)-capped AuNPs are aggregated in the presence of homocysteine (HCys) and cysteine (Cys) but not in the presence of cysteinylglycine, glutathione, and £^-glutamycysteine. When adding NaOH to a solution of HCys, the five-membered ring transition state is formed through intramolecular hydrogen abstraction. By contrast, it is difficult for Cys to form a fourmembered ring transition state after Cys has been pretreated with NaOH. As a result, the HCys-induced aggregation of the FSN-capped AuNPs is suppressed because the five-membered ring transition state exhibits relatively larger steric hindrance and has stronger interaction with the FSN molecules. Thus, we can discriminate between Cys and HCys on the basis of different aggregation kinetics. Under the optimum condition, we have validated the applicability of our method through the analyses of Cys in urine samples. It is believed that this approach has great potential for the detection of Cys in biological samples.

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.