Orientador: Carol Hollingworth Collins / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-18T09:08:43Z (GMT). No. of bitstreams: 1 Souza_EndlerMarcelBorgesde_D.pdf: 24501631 bytes, checksum: 4fd1866c1e1f40857962b738d98e6eb5 (MD5) Previous issue date: 2011 / Resumo: As propriedades cromatográficas e a estabilidade de fases estacionárias preparadas pela imobilização térmica do poli(metiloctilsiloxano) ou do poli(metiltetradecilsiloxano) sobre a sílica foram avaliadas. Para isso, fora empregados os testes de Engelhardt, Tanaka e SRM 870. O estudo dos mecanismos envolvidos na retenção de solutos básicos nestas fases estacionárias foi feita com um teste desenvolvido em nosso laboratório, que consiste em avaliar os fatores de retenção e a assimetria de solutos hidrofóbicas e hidrofílicas em fases móveis com diferentes valores de pH, preparadas com diferentes tipos e concentrações de tampão. A avaliação das fases estacionárias com os testes SRM 870 e de Tanaka mostram uma alta contribuição dos fenômenos de troca iônica para retenção dos solutos básicos e a comparação dos valores obtidos com o teste de Tanaka, segundo o modelo de Euerby, mostrou que estas fases estacionárias apresentam propriedades cromatográficas distintas da maioria das fases comerciais, embora alguma similaridade tenha sido observada com as fases estacionárias que também apresentam altas contribuições de fenômenos de troca iônica na retenção de solutos básicos. O novo teste desenvolvido mostrou que a retenção de solutos básicos acontece devido a interações sinérgicas dos silanóis residuais com os polisiloxanos imobilizados na forma de gotas sobre a sílica. Devido a estas interações, o pH da fase móvel, o tipo e a concentração de tampão afetam intensamente os fatores de retenção e a assimetria de solutos básicos. Algumas das fases estacionárias apresentaram boa seletividade e picos simétricos para solutos básicos em fases móveis neutras, onde os solutos estam protonados e os silanóis residuais estão desprotonados. Os testes de estabilidade demonstraram que algumas das fases estacionárias são altamente estáveis em fases móveis neutras em temperatura ambiente e em fases móveis ácidas, mesmo a altas temperaturas. No entanto, estas se mostraram instáveis em fases móveis alcalinas mesmo em temperatura ambiente, conforme esperado para fases estacionárias preparadas pela imobilização de polissiloxanos sobre a sílica / Abstract: This work has evaluated the chromatographic properties and the stability of stationary phases prepared by with poly(methyloctylsiloxane) or poly(methyltetradecylsiloxane) thermally immobilized onto a silica surface. The stationary phases were chromatographically evaluated using the Engelhardt, SRM 870 and Tanaka tests. The retention mechanisms involved during the separation of basic solutes with these stationary phases were evaluated using a test developed in our laboratory that evaluates the effect of the mobile phases with different pH, and type and concentration of buffer on the retention factors and asymmetry of several basic solutes (with hydrophobic or hydrophilic characteristics). Evaluations with the SRM 870 and Tanaka tests showed that there is a high contribution of ionexchange interactions at neutral pH. Classifications using the Euerby¿s procedure indicate that the stationary phases developed in this work are different from most commercial ones, although some similarity was found with the phases that have high ion-exchange interactions. Also, the retention of basic solutes occurs due to synergetic interactions between the free silanols with the immobilized polysiloxanes, which are in the form of plugs on the silica surface. Due to these interactions the pH of the mobile phase, and the type and concentration of buffer have a strong effect on the retention factors and asymmetry factors of basic solutes. The stationary phases present good selectivity at near neutral pH, where both the basic solutes and free silanols are protonated, suggesting the use of intermediate pH for basic solute analyses. Stability tests show that the stationary phases have high stability in neutral mobile phases at room temperature and also in acidic mobile phases, even at high temperatures. However, these phases have low stability in alkaline mobile phases, even at room temperature, which was expected for polysiloxanes immobilized onto silica / Doutorado / Quimica Analitica / Doutor em Ciências

Under the framework of this PhD project, a study on chromatographic behaviour of selected azaarenes on octadecylsilica stationary phases during their separation by reversed phase liquid chromatography was developed. The main goal was aimed at an application of the basic RPLC principles on the retention behaviour of azaarenes including the effects such as peak tailing, peak broadening, irreproducible retention or strong retention on a stationary phase. This study was particularly focused on basic azaarenes, also called acridines, which belong to a group of persistent organic pollutants providing mutagenic and/or carcinogenic activity. The retention patterns were studied on a group of eight acridines that are often present in environmental samples polluted with polycyclic aromatic compounds. The mixture of acridines was separated under isocratic elution conditions on three octadecylsilica stationary phases using two different binary mixtures as a mobile phase. Evaluation of the surface properties of the selected stationary phases was firstly performed, followed by the separation experiments. The structure of the experiments was designed to evaluate the effect of three different factors on the retention behaviour of acridines: properties of a stationary phase, composition of a mobile phase and physical-chemical properties of acridines. The treatment of the results was based on the capacity factor values providing the best fitting and repeatability of data, but other parameters that evaluate thermodynamic and kinetic aspects of the separation process were also given. Simple correlations between the three factors and a character of retention mechanism of acridines on the given separation system were found. Application of this knowledge simplifies an optimisation process and helps to solve common separation problems for acridines, but also for other basic analytes displaying similar physical-chemical properties (Mr and pKa).