The determination of Na, K, Mg and Ca is part of pure biodiesel (B100) or petroleum diesel blends (B2, B5, B10 etc) characterization. Thus, the determination of these elements is necessary, since their presence above certain levels can change the characteristics of use of the product. This thesis presents optimization and validation studies that support the ABNT NBR 15556, and also the comparison of the performance of LS F AAS and HR-CS AAS in applying this norm for the determination of Na, K, Mg and Ca in biodiesel. Since other factors are likely to become required determinations in biodiesel characterization, this study also presents methods developed for the determination of As and Si in vegetable oils and biodiesel. This study confirmed that Na, K, Mg and Ca can be determined in biodiesel samples obtained from different origins by F AAS, with adequate limits of detection for their characterization according to the current legislation. The proposed method for the determination of As in vegetable oil and biodiesel samples by GF AAS is simple, quick, precise and adequate for the expected limits in Brazilian legislation. The samples, prepared as a three-component solution, in a 1-propanol and nitric acid solution, showed good stability, allowing the automation of the procedure by use of automatic samplers. Low volatile and toxicity solvents were used, allowing external calibration to be performed with standard inorganic or organometallic As solutions. For Si, results indicate that it is possible to perform this elements determination in vegetable oil and biodiesel by HR-CS F AAS, after simple sample dilution with xylene, using external calibration with calibration solutions prepared in a base oil in xylene solution, for viscosity adjustment.