Orientadora: Profa. Dra. Lúcia Helena Gomes Coelho / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência e Tecnologia Ambiental, 2016. / O uso de pesticidas na agricultura e um dos principais fatores de poluicao do solo e das aguas superficiais e subterraneas, sendo potencialmente danoso ao ambiente e a saude humana. Comumente, os residuos de pesticidas estao presentes em concentracoes baixas, o que torna necessaria a extracao e pre-concentracao do analito a fim de elevar a detectabilidade dessas substancias. Neste trabalho, avaliou-se a viabilidade tecnica de aplicacao da metodologia para extracao e pre-concentracao de tracos do herbicida Paraquat, presente em amostras de agua, por extracao em ponto nuvem, minimizando a utilizacao de solventes organicos toxicos e a geracao de residuos, estrategias de preparo de amostra de grande interesse para as areas de tecnologias verdes. Os procedimentos foram realizados utilizando-se diferentes surfactantes: nao ionico (Triton X-114) e ionicos (SDS ¡V anionico e CTAB ¡V cationico). Testou-se a influencia de composto ionico na amostra para auxiliar a separacao das fases e observou-se que, para o sistema SDS/CTAB, a adicao de 10% de NaCl (m/v) ajudou na separacao da fase micelar em relacao a fase aquosa, porem este sistema nao foi eficaz para a extracao do Paraquat devido ao aspecto coloidal da fase organica. Para o Triton X-114, o composto ionico nao apresentou diferenca significativa na separacao das fases, nao justificando a utilizacao do reagente. Este sistema apresentou resposta linear para solucoes entre 0,2 e 5,0 mg L-1 de Paraquat, com FE de 71 e recuperacao entre 62 e 100% para concentracao de 3 mmol L-1 em surfactante, e, FE 45 e recuperacao de 100% para 6 mmol L-1 em surfactante. A solucao de Triton X-114 3 mmol L-1 apresentou repetibilidade em suas extracoes, com coeficiente de variacao medio de 15,5%, porem nao foi reprodutivel. Para quantificacoes em amostras reais, fez-se necessaria a reacao com ditionito para seletividade do Paraquat, pois substancias presentes na amostra podem ser extraidas e absorverem no mesmo comprimento de onda que o analito de interesse (¿Ü = 258 nm). Os limites de deteccao e quantificacao foram, respectivamente, 15 e 50 £gg L-1 para a leitura direta e 50 e 167 £gg L-1 para a determinacao colorimetrica. Contudo, a aplicacao em amostras reais nao apresentou a mesma eficiencia de pre-concentracao e extracao, sobretudo pela elevada solubilidade do Paraquat em agua, concluindo-se que a tecnica nao se mostrou a mais adequada para a aplicacao proposta. A quantificacao por colorimetria e uma alternativa interessante a determinacao por HPLC por ser mais rapida, menos laboriosa e de menor custo, alem do residuo ser de mais facil disposicao que os solventes organicos convencionalmente utilizados em cromatografia. / The use of pesticides in agriculture is one of the main factors of soil, surface and groundwater pollution, and they are potentially harmful to the environment and human health. Pesticides residues are commonly present at low concentrations, which makes necessary an extraction and pre-concentration step of the analyte in order to increase the detectability of these substances. In this work, it was evaluated the feasibility of application of the extraction and pre-concentration of traces of the herbicide Paraquat present in water samples, using cloud point extraction methodology, minimizing the use of toxic organic solvents and the generation of residues, which are considered strategies of sample preparation with huge interest for green technologies. The procedures were performed using different surfactants: nonionic (Triton X-114) and ionic (SDS - anionic and CTAB - cationic). It was tested the influence of ionic compounds in the sample to aid phase separation and it was observed that, for SDS/CTAB system, the addition of 10% NaCl (w/v) helped the micellar phase separation, but this system was not effective for Paraquat extraction once the organic phase produced had a colloidal aspect . For the Triton X-114, the ionic compound was no significant difference, not justifying the use of the reagent. This system showed linear response between 0.2 and 5.0 mg L-1 of Paraquat, with enrichment factor of 71 and recovery between 62 and 100% with the concentration of 3 mmol L-1 in tensoative, and, enrichment factor 45 to 100% recovery for 6 mmol L-1 in surfactant. The solution of Triton X-114 3 mmol L-1 showed repeatability in the cloud point extraction, with mean variation coefficient of 15.5%, but it was not reproducible. For the measurements using real samples, it was necessary a prior reaction with dithionite for selectivity detection of Paraquat, once many substances present in the water sample can be simultaneously extracted and analysed at the same wavelength as the target analyte (ë = 258 nm). The limits of detection and quantification were, respectively, 15 and 50 ìg L-1 for the direct analysis and 50 and 167 ìg L-1 for the colorimetric determination. However, the application in real samples did not show the same efficiency of pre-concentration and extraction, especially because Paraquat has high solubility in the water, concluding that the technique was not the most suitable for the proposed application. The colorimetric quantification is an interesting alternative to HPLC determination because it is faster, less laborious and lower cost, in addition to generating an easier disposition residue than conventionally organic solvents used in chromatography.
| Identifer | oai:union.ndltd.org:IBICT/oai:BDTD:102517 |
| Date | January 2016 |
| Creators | Luiz, Bárbara Alonso Vieira |
| Contributors | Coelho, Lucia Helena Gomes, Matheus, Dácio Roberto, Batista, Guilherme Lopes |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | Portuguese |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Format | application/pdf, 81 f. : il. |
| Source | reponame:Repositório Institucional da UFABC, instname:Universidade Federal do ABC, instacron:UFABC |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | http://biblioteca.ufabc.edu.br/index.php?codigo_sophia=102517&midiaext=72702, http://biblioteca.ufabc.edu.br/index.php?codigo_sophia=102517&midiaext=72703, Cover: http://biblioteca.ufabc.edu.brphp/capa.php?obra=102517 |
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