In this work, twelve heavy metals and arsenic, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, and Zn, in a rice sample collected from some areas of Vietnam have been quantified and implemented by using multiple analytical platforms such as ICP-MS, AAS, and mercury analyser. Seventy rice samples collected from the Red River Delta and mining zone activity were analysed. Concentration of heavy metals and arsenic in rice was analysed after appropriated sample digestion using internal or external calibration curves. The mean concentration (mg kg⁻¹ dried weight) of the analysed elements in rice samples decreased on the order of Mn (19.268)>Fe (13.624)>Zn (8.163)>Cu (3.138)>Ni (0.384)>Cr (0.296)>Co (0.279)>As (0.115)>Cd (0.111)>Pb (0.075)>Hg (0.007)>Se (<LOD). Mercury, a highly toxic element, has been only found in rice samples collected in the mining activity zone (frequency detection 14.5 of total samples). The experimental results indicated that the heavy metals and arsenic found in rice collected from mining activity zone were higher than those in rice harvested from normal cultivated areas like the Red River Delta. The heavy metals and arsenic content in Vietnamese rice samples were also compared with the concentration of heavy metals in other foreign rice samples in some recent publications. The estimated daily intake through rice consumption was calculated and compared with the level proposed by the Food and Agriculture Organization of the United Nations. The results indicated that the provisional daily intake of Cd was higher than the level proposed by FAO, while the intake of other heavy metals was in an acceptable range of CODEX standard.

We report on the performance and durability of four Pt-based cathode catalysts in a microfluidic <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>H2/O2 fuel cell: commercial unsupported Pt and <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co as well as in-house acid-treated <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co ( <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co -at) and <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext><mml:mo>/</mml:mo><mml:mtext>Mo</mml:mtext></mml:mrow></mml:math>Pt3Co/Mo . Commercial <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co was used as the starting material for both <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co -at and <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext><mml:mo>/</mml:mo><mml:mtext>Mo</mml:mtext></mml:mrow></mml:math>Pt3Co/Mo . The composition of the resulting catalysts was confirmed via X-ray photoelectron spectroscopy analysis. In situ cathode studies were performed using an acidic microfluidic <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>H2/O2 fuel cell with an analytical platform. The electrolyte flow rate was optimized to minimize the effects of water management such that fuel cell performance is kinetically limited by the oxygen reduction reaction (ORR). In addition, electrolyte concentration was separately varied to determine cathode performance as a function of acidic pH. All four catalysts demonstrated good short-term activity and stability under fuel cell operating conditions in harsh acidic environments, with the <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext><mml:mo>/</mml:mo><mml:mtext>Mo</mml:mtext></mml:mrow></mml:math>Pt3Co/Mo alloy exhibiting the highest activity. Furthermore, both modified catalysts, <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext><mml:mo>/</mml:mo><mml:mtext>Mo</mml:mtext></mml:mrow></mml:math>Pt3Co/Mo and <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co -at, exhibited superior durability compared to commercially available <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext></mml:mrow></mml:math>Pt3Co and Pt in the accelerated cathode aging studies performed within the microfluidic fuel cell via potential cycling. In situ impedance analysis of the <mml:math display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mtext>Pt</mml:mtext></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mtext>Co</mml:mtext><mml:mo>/</mml:mo><mml:mtext>Mo</mml:mtext></mml:mrow></mml:math>Pt3Co/Mo cathode revealed enhanced catalyst stability and electrode durability as the cause of the dramatic improvements in long-term performance.