Aplicações de tecnicas modernas de espectometria de massas em quimica analitica e em estudos de mecanismos de reações na fase gasosa

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

In this work techniques of mass spectrometry were used to quantify semivolatile compounds in pharmaceutical preparations, for fingerprint of samples of national and imported beers and in the reactions monitoring in aqueous media and in gaseous phase. These studies had been divided in six parts. The biocatalisys reactions monitoring were carried in order to verify the formation of the reduction products from reagents containing carbonyl groups using saccharomyces serevisiae. The monitoring of such processes using the MIMS technique became possible to observe the conversion of reagents used in the products of the reaction. In order to quantify acetylsalicylic acid (AAS), ascorbic acid (Vitamin C) and caffeine in samples of pharmaceutical preparations the DIMP/T&R-MIMS technique was used in order to supply one more alternative of analysis of such compounds in the matrix selected in addition the described techniques already in literature. Giving sequence to the work, the study of a set of samples of national and imported beers of different styles was realized using ESI-MS for the fingerprint of these samples of beer once that the distinct characteristics of each type of beer are reflected in its respective mass spectras. Analysis of principal components (PCA) applied to the mass spectras also was used to to carry through a classification of these samples. In order to verify the transient intermediates formed in solution during the reaction between Tebbe s reagent and vinyl-ethers the solution containing the species formed during this reaction was transferred to the gaseous phase using the APCI-MS technique (Atmospheric Pressure Chemical lonization connected to a mass spectrometer). To get structural informations on the intermediate formed during the reaction the APCI-MS/MS technique (Atmospheric Pressure Chemical lonization followed by CID with an inert gas) was used. The fact of the reaction intermediates to be transient especies becomes impossible the use of traditional spectroscopic techniques (RMN, UV, etc.) for monitoring of this type of reaction. Using pentaquadrupole mass spectrometer halocarbonyl cations XCO (X = F, CI, Br) were reacted with aromatic compounds in gaseous phase in order to promote C-H bond activation of aromatic compounds (M-H) via gas-phase ionic carbonylation. This novel reaction occurs via electrophilic addition followed by prompt HX elimination, forms the respective acylium ions (M-CO+), and competes with electron abstraction and X transfer. Finally, isomeric compounds were characterized by gas-phase structurally diagnostic ion-molecule reactions with acetonitrile using a pentaquadrupole mass spectrometer. This way we intend to distinguish many sets of homologous isomeric ortho, meta and para-acyl and amidyl anilines and phenols with diagnostic fragment ions formed upon 70 eV EI of the isomeric precursor molecules.

ASSUNTO(S)

cerveja espectometria de massa

ACESSO AO ARTIGO

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