ChemWeb Newsletter

Not a subscriber? Join now.February 14, 2006


This week: filtering arsenic from the devil's water, those who pucker up daily will be in the pink, organic zeolites show their mettle, the plastic spectrometer, the water-hockey forest.

Soluble arsenic salts are an insidious health threat to countless people who rely on wells for drinking water, particularly on the Indian sub-continent, where skepticism of tubewells in the 1960s and onwards as offering the "devil's water" have revealed a chilling truth. Now, European researchers have devised a simple and, critically, inexpensive filter that can remove arsenic salts from drinking water. The filter uses iron oxide-coated sand which absorbs the arsenic from water at the source. The device could be cheap enough for even the poorest families in affected regions of the developing world to afford. Furthermore, there are potential users in wealthier places too, such as remote farms that are not connected to mains water in countries, such as Australia, New Zealand, and Argentina as well as Hungary and Serbia. These regions too all have documented arsenic levels above WHO safety margins.

Red grapefruit appears to lower cholesterol and fight heart disease, according to Shela Gorinstein and colleagues at the Hebrew University of Jerusalem. She and her team fed 57 patients following coronary bypass surgery one of three daily citrus options for a month - red grapefruit, white (blonde) grapefruit, no grapefruit - alongside normal, healthy meals. Those taking red grapefruit on a daily basis had significantly lower levels of blood lipids compared to the "blondes" and those who didn't pucker up for daily citrus. Gorinstein and colleagues suggest that antioxidants in red grapefruit or perhaps another compound is responsible for the benefits.

Mohamed Eddaoudi and colleagues at the University of South Florida have developed a molecular building block approach to constructing zeolite-like metal-organic frameworks (ZMOFs). The compounds are based on replacing the oxygen that bridges the tetrahedral building units with a longer organic linker. The new materials have structures very similar to conventional inorganic zeolites as well as extra large cavities. Such compounds could be useful as catalysts, sensor materials, or molecular sieves. Moreover, their foundation in metal-organic, rather than inorganic chemistry could allow them to be fine-tuned more readily than their inorganic counterparts for particular applications.

On the whole spectrometers are bulky instruments with limited portability. But, Ali Adibi of the Georgia Institute of Technology hopes to change all that. He and his colleagues have developed a technology to help reduce the number of parts needed by a spectrometer. Conventional spectrometers have a narrow slit, a lens, a grating, a second lens and a detector. The GaTech team has now combined these different components into a volume hologram formed from an inexpensive chunk of polymer and a detector to create a compact, efficient and inexpensive spectrometer that could be used for multiple spectroscopy and sensing applications.

A surface that treats water droplets like so many air-hockey pucks has been developed by researchers at the University of California at Los Angeles. The surface reduces the friction between itself and water droplets by creating a cushion of air between the two acting like an air-hockey table. The big difference is that rather than a grid of air holes, the surface is coated with a forest of micrometer posts etched across the surface. The posts trap air allowing a fluid to flow across it with greatly reduced friction, it is almost like an inverted hydrofoil effect. Such a scheme has been tried before, but the UCLA researchers have the sharpest posts and the highest yet density of posts so far. This is important for certain areas for fluid research and for prospective microfluidic applications, as well as for making submarine craft more efficient by reducing drag.