Levels of major, minor and toxic metals in tubers and flour of Dioscorea abyssinicagrown in Ethiopia

Dioscorea abyssinica, commonly known as yam, is an indigenous plant in Ethiopia. Its root tuber is used as staple and co-staple food in South Nation Nationality People and Regional State of Ethiopia. This study was carried out to analyze the selected mineral nutrients in the tuber and flour of D. abyssinica grown in different parts of the country for human consumption. Samples collected from five different areas were analyzed for eleven metals (Ca, Mg, Fe, Zn, Cu, Mn, Co, Cr Ni, Cd and Pb) by flame atomic absorption spectrometry and two metals (K and Na) by flame emission spectrometry. Known weight of oven-dried sample was  wet-digested using 3 mL of (69–72%) HNO3 and 1 mL of (70%) HClO4, for 2 h at variable temperature (120–270 oC). The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recovery was in the range of 92–105%. The mean concentration range (in ìg/g) of each metal in D. abyssinica samples were K (8,469–13,914), Na (133–405), Ca (172–448), Mg (180–354), Fe (28.3–144.5), Mn (12.0–14.5), Zn (12.3–44.5), Cu (7.26–17.6), Co (1.91–8.68), Cr (0.86–3.41) and Ni (2.43–5.31). D.abyssinica could be good sources of essential trace metals to the individuals, more particularly Fe and Zn were higher than the entire trace metals in the samples investigated while Cd and Pb were in minor quantities and hence the plant is free from toxic heavy metals. Consuming 100 g of this tuber per day contribute the following concentration range of Fe, Zn, Cu, Mn, Co, Ni and Cr in mg/100 g per day: 2.8–14.4, 1.2–4.5, 0.73–1.8, ND–1.5, ND–0.87, 0.24–0.53 and 0.09–0.34 mg/100 g,respectively. Statistical analysis revealed that significant variations in metal concentrations among the sampling sites were observed for some of the metals when pair wise test was made while insignificant variation were seen for the remaining metals. D. abyssinica could be a better source of K, Ca, Fe and Zn to human compared to the common cereal flours (barley, wheat and red teff flour) as well as tuber food products like potato, cassava, yam, and enset (Ensete ventricosum), while it could be an alternative source of the other essential mineral nutrients to the individual daily mineral intake.Key words: Root tuber, Dioscorea abyssinica, metals, Ethiopi

Levels Of Major, Minor And Toxic Metals In Tubers And Flour Of Dioscorea Abyssinica Grown In Ethiopia

Dioscorea Abyssinica , commonly known as yam, is an indigenous plant in Ethiopia. Its root tuber is used as staple and co-staple food in South Nation Nationality People and Regional State of Ethiopia. This study was carried out to analyze the selected mineral nutrients in the tuber and flour of D. abyssinica grown in different parts of the country for human consumption. Samples collected from five different areas were analyzed for eleven metals (Ca, Mg, Fe, Zn, Cu, Mn, Co, Cr, Ni, Cd and Pb) by flame atomic absorption spectrometry and two metals (K and Na) by flame emission spectrometry. Known weight of oven-dried sample was wet-digested using 3 mL of (69–72%) HNO3 and 1 mL of (70%) HClO4, for 2 h at variable temperature (120–270° C). The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recovery was in the range of 92–105%. The mean concentration range (in μg/g) of each metal in D. abyssinica samples were K (8,469–13,914), Na (133–405), Ca (172–448), Mg (180–354), Fe (28.3–144.5), Mn (12.0–14.5), Zn (12.3–44.5), Cu (7.26–17.6), Co (1.91–8.68), Cr (0.86–3.41) and Ni (2.43–5.31). D. abyssinica could be good sources of essential trace metals to the individuals, more particularly Fe and Zn were higher than the entire trace metals in the samples investigated while Cd and Pb were in minor quantities and hence the plant is free from toxic heavy metals. Consuming 100 g of this tuber per day contribute the following concentration range of Fe, Zn, Cu, Mn, Co, Ni and Cr in mg/100 g per day: 2.8–14.4, 1.2–4.5, 0.73–1.8, ND–1.5, ND–0.87, 0.24–0.53 and 0.09–0.34 mg/100 g, respectively. Statistical analysis revealed that significant variations in metal concentrations among the sampling sites were observed for some of the metals when pair wise test was made while insignificant variation were seen for the remaining metals. D. abyssinica could be a better source of K, Ca, Fe and Zn to human compared to the common cereal flours (barley, wheat and red teff flour) as well as tuber food products like potato, cassava, yam, and enset ( Ensete ventricosum ), while it could be an alternative source of the other essential mineral nutrients to the individual daily mineral intake

Synergistic Effects of PdOx?CuOx Loadings on Methyl Mercaptan Sensing of Porous WO3 Microspheres Prepared by Ultrasonic Spray Pyrolysis

In this work, PdOx-CuOx co-loaded porous WO3 microspheres were synthesized with varying loading levels by ultrasonic spray pyrolysis (USP) using polymethyl methacrylate (PMMA) microspheres as a vehicle template. The as-prepared sensing materials and their fabricated sensor properties were characterized by X-ray analysis, nitrogen adsorption, and electron microscopy. The gas-sensing properties were studied toward methyl mercaptan (CH3SH), hydrogen sulfide (H2S), dimethyl sulfide (CH3SCH3), nitric oxide (NO), nitrogen dioxide (NO2), methane (CH4), ethanol (C2H5OH), and acetone (C3H6O) at 0.5 ppm under atmospheric conditions with different operating temperatures ranging from 100 to 400 °C. The results showed that the CH3SH response of USP-made WO3 microspheres was collaboratively enhanced by the creation of pores in the microsphere and co-loading of CuOx and PdOx at low operating temperatures (≤200 °C). More importantly, the CH3SH selectivity against H2S was significantly improved and high selectivity against CH3SCH3, NO, NO2, CH4, C2H5OH, and CH3COCH3 were upheld by the incorporation of PdOx to CuOx-loaded WO3 sensors. Therefore, the co-loading of PdOx-CuOx on porous WO3 structures could be promising strategies to achieve highly selective and sensitive CH3SH sensors, which would be practically useful for specific applications including biomedical and periodontal diagnoses

Photochemical Kinetics of Pyruvic Acid in Aqueous Solution

International audiencePyruvic acid in the atmosphere is found in both the gas and aqueous phases, and its behavior gives insight into that of other alpha-keto acids. Photolysis is a significant degradation pathway for this molecule in the environment, and in aqueous solution the major photoproducts are higher-molecular-weight compounds that may contribute to secondary organic aerosol mass. The kinetics of the aqueous-phase photolysis of pyruvic acid under aerobic and anaerobic conditions was investigated in order to calculate the first-order rate constant, J(aq), in solution. Analysis of the exponential decay of pyruvic acid was performed by monitoring both pyruvic acid and its photolytic products over the course of the reaction by H-1 NMR spectroscopy. Detection of major and minor products in the 0.1, 0.05, and 0.02 M pyruvic acid photolyses clearly demonstrates that the primary reaction pathways are highly dependent on the initial pyruvic acid concentration and the presence of dissolved oxygen. The J(aq) values were calculated with approximations based on the dominant pathways for limiting cases of the mechanism. Finally, a model study using the calculated rate constants demonstrates the importance of aqueous-phase photolysis as a sink for pyruvic acid in the atmosphere, compared with gas-phase photolysis and OH oxidation