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The effect of selenate and selenite enrichment on mineral composition of a red type of lettuce cv. "Veneza roxa" was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP OES), molecular modeling and principal component analysis (PCA). Both Se species did not show toxicity, while selenate promoted the greatest Se accumulation by the plant. There was an increase of 886 µg of Se per 100 g of fresh sample at different concentrations of selenate, but for selenite the maximum variation was only of 114 µg per 100 g. Selenate promoted the absorption of Mo and S and the reduction of K, Mn and P, meanwhile selenite increased Mn and decreased Mo accumulation. Copper and Fe absorption was negatively affected, Ca and Mg showed a slight increase, and Na and Zn were not affected by Se species. Despite the changes in the nutritional balance, Se-enriched lettuce can still be considered a potential dietary source of this essential element.

In this paper, a comparative study between three acid decomposition procedures of milk powder samples for the determination of Ca, Cu, Fe, K, and Na by optical emission spectrometry with inductively coupled plasma is presented. Utilizing a reflux system, it was possible to increase the temperature of the digester block above the boiling point of the reaction medium, avoiding the loss of analyte and the excessive evaporation of the acids during the heating. Conditions of acidity (10 mL HNO 3 /H 2 SO 4 ), temperature (350°C), and decomposition time (4 h) were defined by evaluation of residual carbon content. Acid digestion in an open system with a cold finger was compared with a conventional open system (4 h ate 120°C), as well as with microwave digestion (heating ramp to 180°C by the time 45 min), for four commercial samples of milk powder. For the three sample preparation procedures, the values of the analyte concentrations in all analyzed samples were similar. The accuracy of the acid digestion procedures for Ca, Cu, Fe, K, and Na was assessed by the analysis of a certified reference material of milk (infant formula), and good agreement between the certified values and the measured value was obtained. The limits of quantification for the acid digestion with reflux system for Ca, Cu, Fe, K, and Na, in milligram per kilogram, were 7. 48, 0.31, 1.0, 8.20, and 25.81, respectively, and for the microwave digestion were 14.0, 0.57, 1.78, 14.65, and 46.08, respectively. The decomposition procedure using a cold finger in an open system is effective, presenting the lowest residual carbon content (6 %), good accuracy, and relative standard deviation lower than 5 %, and appears to be a suitable procedure for sample preparation for routine analysis.