Síntese e caracterização de materiais sorventes baseados em sílica modificada com titânio e PMODS para uso em extração de fase sólida (SPE)

Abstract

In Brazil, the agricultural activities play a fundamental role in the economy. However, the intensification of the use of pesticides by humans trying to protect their plantation and products leads to a water and soils contamination. Executing direct analysis to identify pollutants and contaminants is a complicated task, once they have low concentrations and they are in complex matrices with lots of interfering substances. Those substances may infer gross errors while expressing analytical results. It is necessary to fulfil a previous sample preparation step as it is crucial to perform the analyses. Nowadays there are different techniques available to execute the sample preparation, but solid phase extraction has been standing out because it is extremely efficient when it comes to eliminate interfering agents, to concentrate compounds and to consume low organic solvents. The SPE technique complies with the Green Chemistry principles. Commonly, cartridges in the form of syringes filled with solid phases are used, these phases are very important to accomplish success when the technique is being used, it requires to take some conditions of the analytes and matrices before to choose the right sorbent material. There are many commercial and labmade sorbent materials available, and in this context, silica has been receiving the highlight due its low cost and high yield. Thus, this work had as a main objective the development, physicochemical and chromatographic characterization of a sorbent material made of silica titanium and poly(methyloctadecylsiloxane), PMODS, to be used in the solid phase extraction of water samples contaminated with some pesticides applied to soybean, corn and cotton plantations in the state of Mato Grosso. The material preparation began with the metallization of chromatographic silica with Ti alkoxide, going through the step of polymer sorption to the support and then thermal immobilization, in the oven, under two different conditions: 100ºC for 17,36h and 120ºC for 16h, after this step its characterization could be executed. The FTIR confirmed the support modification with PMODS, showing absorption bands around 2930 cm-1 and 2850 cm-1 and it also suggests that some silanol groups were replaced on the support by titanol groups by the appearance of bands around 980 cm-1 Scanning electron microscopy and X-ray dispersion spectroscopy revealed the deposition of PMODS above the support with sizes of 477,76 nm and 105,20 nm and also the incorporation of titanium on the surface of the modified support which was 1.9% (m/m). The success in this stage of preparations and physicochemical characterization of the sorbent material developed in this project enables the research to be continued in a future stage with the material’s chromatographic characterization through the application in solid phase extraction of water samples contaminated with pesticides and other organic contaminants.