Detalhes bibliográficos
| Ano de defesa: |
2014 |
| Autor(a) principal: |
Delfino, José Rodrigues
 |
| Orientador(a): |
MARQUES, Aldaléa Lopes Brandes
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| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Dissertação
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal do Maranhão
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| Programa de Pós-Graduação: |
PROGRAMA DE PÓS-GRADUAÇÃO EM QUÍMICA/CCET
|
| Departamento: |
QUIMICA
|
| País: |
BR
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| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://tedebc.ufma.br:8080/jspui/handle/tede/981
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Resumo: |
The moisture in biodiesel is an important parameter that should be monitored to ensure the final quality of the biofuel. We have developed a new and alternative method for determination of this parameter in biodiesel by electrochemical impedance spectroscopy. The method is based on the variation of the resistance to charge transfer medium depending on the amount of water in the biodiesel as a treatment of the sample using a simple dilution of samples of biodiesel in acetonitrile. Operating parameters optimized for the quantification of water content by electrochemical impedance were: 10 mV amplitude, time OCP = 20s, frequency range 10⁶ to 10ˉ¹ Hz and points per frequency decade = 10. In optimized conditions was obtained a good linear correlation between the resistivity of the medium and the water content, which allowed the determination of this parameter on samples of biodiesel. A substantial change in charge transfer resistance was observed with the additions of water in the sample solution, confirming the viability of the analytical method under study. The procedure was applied to samples of biodiesel and statistically validated, the results were considered satisfactory. The accuracy of the method was checked by recovery tests (ranging from 96.15% to 102.69%), and also application of Student's t-test, with concordant results, as there was no significant difference between the averages obtained by this method (Sample1 = 460.6 mg kgˉ¹ and Sample2 = 512.7 mg kgˉ¹) and the average obtained by the official method, Norma ANP 14/12 (Sample1 = 486.8 mg kgˉ¹ and Sample2 = 540,6 mg kgˉ¹) for a confidence level of 95%. The precision showed a coefficient of variation less than 5%. Average detection limits of 1.77 mg kgˉ¹for the samples proved the good sensitivity (10.1 Ω/cm2.Kg.mgˉ¹) of the proposed method. The values obtained for water content of the samples were between 270.3 ± 3.4 mg kgˉ¹ and 540.6 ± 12.9 mg kgˉ¹ for the water content in the samples of biodiesel certified by the program interlaboratory ANP. |
