Determination of selected major and trace metals in lemongrass (Cymbopogon citratus) by microwave plasma-atomic emission spectrometry

Cymbopogon citratus is very important and of great interest due to its commercially valuable essential oils, its common use in food and beverage industries as well as in traditional folk medicine. The objective of the present study was to determine the levels of selected major (K, Mg, Ca) and trace (Mn, Fe, Cu, Zn, and Pb) metals in lemongrass (Cymbopogon citratus) samples collected from Addis Ababa, Ankober, Finote Selam (Gojjam), and Wondogenet by microwave plasma-atomic emission spectrometry. The optimized wet acid digestion method for the analysis of lemongrass was found efficient for all the metals and it was evaluated through the recovery test and good percentage recovery of 86.9 to 106% was obtained for all the metals identified. The metals K, Ca, Mg, Fe, Mn, Cu, Zn and Pb were with a concentration of 743.8-1020, 123.1-129.3, 23.9-36.3, 10.35-22.3, 10.0-12.7, 1.48-2.53, 0.59-1.07, 0.13-0.20 mg/kg, respectively. The results of the Pearson correlation showed that there was a weak and strong positive correlation between the concentrations of the metals analyzed. Statistical analysis by using one-way anova indicated that there were significant differences in the mean concentrations of all the metals (except Ca and Mn) across each sampling points. The results also showed that Cymbopogon citratus are beneficial sources of essential metals. The levels of the metals in the analyzed samples were within the who maximum permissible limits and thus safe for human consumption

Levels of selected metals in Ficus sur Forssk fruit and soil of the plant grown in different parts of Ethiopia

Ficus sur Forssk is one of the wild edible plants in Ethiopia. Its fruits are commonly used in different parts of Ethiopia. Ficus sur fruits and the soil of plant were collected from three different region of Ethiopia. Levels of selected metals (K, Ca, Mg, Fe, Mn, Zn, Cu, Cd, and Pb) in the fruit and soil were determined by microwave plasma-atomic emission spectroscopy. The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recoveries were in the range of 90.5-108%. The concentration range of metals (mg/kg) in Ficus sur fruit samples were K (12372-13687), Ca (3261-5389), Mg (744-785), Fe (418-479), Zn (23.9-25.4), Mn (9.13-18.0), Cu (6.78-7.97), Pb (2.45-6.23) and Cd (0.76-1.42), respectively and in the soil were in the range of 1406-5566 (K), 1248-1453 (Mg), 3140-9403 (Ca), 1186-2421 (Mn), 89763-96704 (Fe), 7.33-13.4 (Pb), 41.4-73.4 (Cu), 123-157 (Zn) and not detected Cd). Ficus sur fruit contains all the essential metals to human. However, it also contains toxic metals Cd at trace level and Pb at higher level than World Health Organization permission level

Reasons for the Differences in the Kinetics of Thermal Oxidation of the Support in Pt/C Electrocatalysts

High-temperature oxidation processes of carbon microparticles Vulcan XC72 coated with platinum nanoparticles (Pt/C) were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The presence of different specific temperature ranges in the oxidation of carbon support was shown to be due to both the peculiarities of granulometric composition of carbon black microparticles, different size, and uneven spatial distribution of platinum nanoparticles in the pores and on the surface of the carbon support. The correlation between the length of a section in the thermograms and the fraction of carbon microparticles poorly coated with platinum can be used to analyze the uniformity of Pt nanoparticle spatial distribution in the metal–carbon catalysts and therefore to select electrocatalysts with optimal microstructure. This analysis is expected to be effectively utilized in order to assess the uniformity of platinum distribution on carbon microparticles and also to provide additional information about granulometric composition of carbon supports