Method development for the determination of manganese in wheat flour by slurry sampling flame atomic absorption spectrometry

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-1 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 mu g g(-1) and a precision, expressed as relative standard deviation (RSD) of 3.5% (n = 10) for a manganese content of about 7.6 mu g g(-1) 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 mu g g(-1). The results showed no significant differences with those obtained after complete digestion of these samples and manganese determination also using FAAS. (c) 2005 Elsevier Ltd. All rights reserved.