Desenvolvimento da sequência de pulso RK-ROSE e aplicações em RMN-DT para analise de componentes sólidos

Abstract

Time domain nuclear magnetic resonance (TD-NMR) typically use lowcost benchtop equipment. TD-NMR is used for both homogeneous and heterogeneous material analyses, in quality control of food, petroleum and derivatives, cosmetics and polymers. Even in the case of heterogeneous materials containing solid and liquid substances, TD-NMR analyzes are mainly based on the liquid part, which has a slow decay, even seconds, due to the high molecular mobility. The analysis of solid components in foods, polymers and other organic materials are studied in less extensión, because the signal decays in some microseconds and are difficult to detect. The purpose of this doctoral thesis is to evaluate the performance of a new pulse sequence designed to refocus the signals of the rigid components of a sample. The main advantage of these sequences is that for its application it is not need extra accessories and therefore can be applied to bench-top TD-NMR equipment and cheap. A new pulse sequence called Rhim-Kessemeier-Radiofrequency Optimized Solid-Echo (RK-ROSE) has been proposed that has higher efficiency than the most commonly used sequences for solid state sample characterization and reaction kinetics monitoring, for example, the Solid-Echo (ES) sequence and "mixed -Magic Sandwich Echo" (mixed-MSE). The RK-ROSE sequence has been evaluated for some applications which include: a) determination of solid components in different samples, for example for polystyrene (PS) and the sequence provided approximately 98% efficiency; b) to solve the reaction kinetics parameters, such as velocity constant (Kc) at different temperatures and to determine the activation energy ( ) of the Araldite epoxy resin polymerization; c) as a method for determining spin-lattice or spin-longitdinal (T 1 ) and spin-spin (T 2 ) relaxation time in solid materials, resulting in 2D experiments to obtain T 1 and T 2 ; d) as a mobile phase filter in experiments to study the molecular dynamics of polymers at different temperatures; and e) as an alternative method to determine solid fat content (SFC) in different samples of butter and cocoa butter, this new method had satisfactory results with the advantage of not using calibration standards.