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The wheat is one of the cereals more consumed in the human food in all worlds. In the form of flour it is used for preparation of breads, cookies, pizzas, cakes, and etc. This way, the knowledge of the mineral content this cereal and its flour is very important. Considering it, methods for determination of metals in these matrices are opportune and several papers have been performed. In this paper, a slurry sampling flame atomic absorption spectrometric method for the determination of manganese in wheat flour is proposed. The optimization step was performed using univariate methodology involving the variables: nature and concentration of the acid solution for slurry preparation, sonication time and sample mass. The established experimental conditions after optimization recommend a sample mass of 0.5 g, 2.0 mol L À1 nitric acid solution and a sonication time of 15 min. This method allows the determination of manganese in wheat flour using the standard calibration technique, with a detection limit of 0.13 lg g À1 , and a precision, expressed as relative standard deviation (RSD) of 3.5% (n = 10) for a manganese content of about 7.6 lg g À1 and using a wheat flour mass of 0.5 g. The accuracy was confirmed by analyzing of three certified reference materials of rice flours. The proposed method was applied for the determination of manganese in seven samples of wheat flour acquired in supermarkets from Salvador City, Brazil. In these, the manganese content varied of 5.2 and 7.6 lg g À1. The results showed no significant differences with those obtained after complete digestion of these samples and manganese determination also using FAAS.

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A simple method for mercury determination in petroleum fractions (e.g. naphtha) using electrothermal atomic absorption spectrometry (ETAAS) associated with multiple injection technique for direct preconcentration in the graphite tube has been developed. Oil-in-water microemulsions (three-component solutions) were prepared using a mixture of sample, propan-1-ol and HNO 3. No additional sample pretreatment was required. In the procedure, three successive 30 mL micro-emulsion aliquots are delivered to the graphite tube. The pyrolysis and atomization temperatures were set to 400 1C and 1400 1C, respectively. The calibration curves showed a linear response up to analyte concentrations of 150 mg L À1 with a correlation coefficient of 0.993. The precision calculated from fifteen consecutive measurements and defined as the coefficient of variation of solutions containing 5.0 and 30 mg L À1 of Hg were 6.4% and 4.7%, respectively. The limit of detection (LOD), defined as the Hg concentration that gives a response equivalent to three times the standard deviation (s) of the blank (n = 10), was found to be 0.78 mg L À1. The proposed procedure was used for mercury determination in naphtha feeds processed in Braskem S.A.