Publicação
A mass spectrometry study of compounds with environmental and biological interest
| Resumo: | The leading thread of this work is the application of Mass Spectrometry to the study of environmental and biological relevant compounds. Several studies were performed involving the development and optimization of efficient analysis methodologies, the behaviour of the compounds under study was investigated using various mass spectrometry techniques and fundamental studies were carried out, most of them complemented with semi-empirical calculations. Matrix-Assisted Laser Desorption/Ionization (MALDI) has been extensively used for the analysis of large molecules. Nevertheless, since the technique provides soft and efficient ionization of thermolabile and non-volatile organic compounds, we decided to investigate its application to small molecules as an alternative ionization method. For that we compared the performance of nanosized TiO2 anatase as matrix with that of common organic matrices. The formation of organic matrix-flavonoid cluster ions was also investigated and it was found to be dependent of the structure of the flavonoid. Aniline derivatives are of great industrial importance and several constitute a significant group of pollutants. The gas-phase behaviour of halo- and nitroanilines under electrospray ionization mass spectrometry conditions was studied. Isomer identification methodologies are proposed using for that purpose competitive fragmentations of protonbound heterodimers. Preliminary results on the behaviour of the aniline derivatives when subjected to electron capture dissociation conditions are presented and discussed. The behaviour of five isoflavones was studied under electrospray ionization mass spectrometry in the positive ion mode. The fragmentation mechanisms were proposed taking into account MSn experiments, accurate mass measurements and semi-empirical calculations. Some of the fragmentations were found to be dependent on the substitution pattern of the B-ring and the ions afforded by these fragmentations can be considered as diagnostic ions. Several newly synthesized -lactones, fused or C-C linked to sugar rings, were studied. Their fragmentation mechanisms were proposed taking into account MSn experiments and semi-empirical calculations. FTICR-MS; ESI; MALDI; Fragmentation Mechanisms; Collision Induced Dissociation |
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| Autores principais: | Madeira, Paulo J. Amorim |
| Assunto: | Espectrometria de massa Química analítica Teses de doutoramento - 2010 |
| Ano: | 2010 |
| País: | Portugal |
| Tipo de documento: | tese de doutoramento |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | The leading thread of this work is the application of Mass Spectrometry to the study of environmental and biological relevant compounds. Several studies were performed involving the development and optimization of efficient analysis methodologies, the behaviour of the compounds under study was investigated using various mass spectrometry techniques and fundamental studies were carried out, most of them complemented with semi-empirical calculations. Matrix-Assisted Laser Desorption/Ionization (MALDI) has been extensively used for the analysis of large molecules. Nevertheless, since the technique provides soft and efficient ionization of thermolabile and non-volatile organic compounds, we decided to investigate its application to small molecules as an alternative ionization method. For that we compared the performance of nanosized TiO2 anatase as matrix with that of common organic matrices. The formation of organic matrix-flavonoid cluster ions was also investigated and it was found to be dependent of the structure of the flavonoid. Aniline derivatives are of great industrial importance and several constitute a significant group of pollutants. The gas-phase behaviour of halo- and nitroanilines under electrospray ionization mass spectrometry conditions was studied. Isomer identification methodologies are proposed using for that purpose competitive fragmentations of protonbound heterodimers. Preliminary results on the behaviour of the aniline derivatives when subjected to electron capture dissociation conditions are presented and discussed. The behaviour of five isoflavones was studied under electrospray ionization mass spectrometry in the positive ion mode. The fragmentation mechanisms were proposed taking into account MSn experiments, accurate mass measurements and semi-empirical calculations. Some of the fragmentations were found to be dependent on the substitution pattern of the B-ring and the ions afforded by these fragmentations can be considered as diagnostic ions. Several newly synthesized -lactones, fused or C-C linked to sugar rings, were studied. Their fragmentation mechanisms were proposed taking into account MSn experiments and semi-empirical calculations. FTICR-MS; ESI; MALDI; Fragmentation Mechanisms; Collision Induced Dissociation |
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