ter me orientado com grande sabedoria e dedicação, por ter sido meu amigo quando precisei, por ter me corrigido quando errei e pelos incansáveis ensinamentos.Ao Luiz Bravo, por ter me dado a oportunidade de crescer profissionalmente e por ter sempre acreditado em mim.Ao Prof. Dr. Julio Cesar Jose da Silva pela contribuição com ideias importantes.Ao Thiago, pelo incrível companheirismo e inestimável ajuda para a conclusão desse trabalho, pelos momentos felizes e pelo carinho, mesmo durante os momentos mais difíceis. À minha família, especialmente aos meus pais, Maria Cristina e Antônio Carlos, e minha irmã, Flávia, pelo apoio incondicional e por terem me ensinado a sempre querer aprender mais.Aos meus colegas de laboratório, Alexandre, Alexandre Fioroto, e, em especial, ao Maciel, que me ajudou quando mais precisei, pelas importantes discussões e pelos cafezinhos no meio do trabalho.Aos meus colegas da Nova Analítica, pela ajuda e compreensão.Às minhas amigas Janaina, Mariana, Daniela e Aline pela compreensão e por todos os momentos divertidos. À Nova Analítica por permitir a realização dessa pesquisa e pela disponibilização do equipamento.Ao Cempeqc pelas amostras e sugestões.Ao CNPq, FAPESP e INCTAA pelo auxílio financeiro ao grupo."Science never solves a problem without creating ten more." ABSTRACT Rainone R. Evaluation of analytical methods for the determination of Na, K, Ca, Mg, P and S by ICP OES. 2011. 95p. Masters Thesis -Graduate Program in Chemistry.The present work has evaluated three different sample preparation methods for determination of Na, K, Ca, Mg, P and S in Biodiesel by ICP OES. The first one was similar to the method required by ANP for Biodiesel quality control, based on the introduction of organic samples into the ICP. In this case, the samples were analyzed with and without dilution in organic solvents (kerosene or xylol). Even though this sample preparation procedure has shown to be very simple, the physical interferences observed were severe and required the use of two different strategies to be overcome: addition of high viscosity oil (vaseline) to the calibration solutions and carbon as internal standard. The second method was based on the introduction of Biodiesel emulsion into the ICP. These emulsions were prepared by the addition of 500 mg of sample, 1% w v -1 Triton X-100 as emulsifying agent and 10% v v -1 of nitric acid in ultrapure water up to 10 mL of final volume. Although this simple sample preparation method has eliminated the challenges associated with the use of organic solvents, the blank solution presented a high concentration of some analytes, due to the contamination by the emulsifying agent and this method generated results with high blank signal and standard deviation. The third method was based on microwave assisted digestion of Biodiesel samples. This method was the only one capable of eliminating the organic matrix and all the challenges associated with it, which made the sample introduction easier and improved the method detection limits. Nevertheless, the time c...