Bioaccessibility and risk assessment of essential and non-essential elements in vegetables commonly consumed in Swaziland.

The green leafy vegetables (Mormodica involucrate, Bidens pilosa and Amaranthus spinosus) are economic; seasonal; locally grown and easily available; easy to propagate and store; highly nutritious food substances that form an important component of diets. This study applies a physiology based extraction technique (PBET) to mimic digestion of these vegetables to determine the fraction of essential (Fe and Zn) and non-essential elements (Cd, Cr and Pb) that are made available for absorption after ingestion. Prior to the application of the PBET, the vegetables were cooked adopting indigenous Swazi cooking methods. Cooking mobilized most of the metals out of the vegetable mass, and the final substrate concentrations are: raw > cooked > supernatant for all the metals, and the order of average metal leaching was: Pb (82.2%) >Cr (70.6%) >Zn (67.5%) >Fe (60.2%) >Cd (53.6%). This meant that the bioavailable concentrations are significantly lower than in the original vegetable mass, if only the solid mass is consumed. Bioaccessibility was higher in the gastric tract than in the intestinal phases of the PBET for all the metals in all the vegetables. Risk assessment protocols employed on the non-essential elements (Cr, Cd and Pb) showed that the associated risks of ingesting metal contaminated vegetables are higher for children, than they are for adults, based on the target hazard quotient (THQ) index. However, the overall health risk associated with ingestion of these metals is low, for both children and adults, based on the HR index. Conclusively, this study expounds on the nutritional and risk benefits associated with ingesting naturally grown vegetables.

Hexamethylenetetramine-Precipitated α-Ni(OH)2 as Precursors for NiO Nanoparticles: Structural and Morphological Characterization.

Influenced by their morphology, nanocrystalline nickel hydroxide and nickel oxide have important technical applications. A simple novel procedure allows for the preparation of α-Ni(OH)2 from nickel nitrate using hexamethylenetetramine (HMTA) as the precipitating agent. The product obtained is free of water, but contains intercalated nitrate and HMTA. Hydroxide samples prepared in this manner decompose in a single step at 350 degrees C and can be used as precursors for NiO. The hydroxide and oxide samples were characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and nitrogen physisorption. Depending on the solvent system used during synthesis, a-Ni(OH)2 has a leaf-like or a flower-like morphology. The nickel oxides obtained from these samples consist of nanocubes (average particle size: 15 nm) and nanorods (length: 30-60 nm), respectively. The oxide samples are mesoporous and the corresponding surface areas are 40 and 35 m2/g.