Aplicação de campos elétricos e materiais nanoestruturados por layer-by-layer no preparo de amostras de saliva e outras matrizes complexas

Abstract

The need to determine compounds in low concentrations from complex matrices, such as biological samples, makes the development of sample preparation techniques a great challenge and a constant task. In this context, this work proposes the use of electric fields, the development and application of Layer-by-Layer (LBL) nanostructured materials in extraction processes. The first strategy is developed in Chapter III and presents three applications of multiphase electroextraction (MPEE) using a commercial paper point. The paper point was first characterized, which presented important characteristics for a support and sorbent, such as compositional simplicity (predominantly cellulose), porosity, hydrophilicity and physical and chemical stability. The method using MPEE and UHPLC-MS/MS was efficient for the determination of cocaine in saliva, while the methods using MPEE, UHPLC-PDA and DIA (DIA; digital image analysis) were efficient for the determination of doxorubicin in saliva. Both presented acceptable and adequate figures of merit for the proposed objective, including selectivity. It is worth mentioning the compatibility of MPEE with different separation and detection techniques and, therefore, its versatility. In Chapter IV, the other strategy was based on the development of nanostructured films by LBL and application in the extraction of drugs and insecticides. For this, the (PDDA/MWCNT)10 film was deposited on the paper point and on borosilicate bottle. Linear deposition of the 10 bilayers was confirmed by UV-Vis spectroscopy and film morphology was evaluated. The paper point-(PDDA/MWCNT)10 was applied to the MPEE of the different compounds from saliva, which were later determined by UHPLC-MS/MS. In this case, the coating of the paper material did not favor the extraction. In contrast, borosilicate bottle-(PDDA/MWCNT)10 showed positive results for the extraction of these compounds from saliva. This application has expanded to urine and surface water sampling, achieving a significant increase of the analytical signal by at least 12 times. Furthermore, these materials can be reused. Finally, the strategies used, the materials and methods developed represent great advances in the area of sample preparation and can still be explored for several applications.