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Never let it be said that scientists have little regard for the world around them. Many chemistry labs are taking on board the principles of green chemistry, in an effort to minimise the effects of their work on the environment. In the latest example, a method for extracting drugs from biological fluids uses no organic solvents, replacing them with plant oils to eliminate hazardous waste. Despite the best efforts of press officers, the general public still regard chemical companies in a poor light, being responsible for chemicals in food and as instigators of pollution. Any kudos achieved by reports of a new drug for treating a powerful disease are immediately swept aside by the latest accidental chemical spillage into a major river, killing fish stocks and threatening water supplies. I have had many discussions with non-scientific friends defending my profession against isolated incidents and have come to realise that the positive aspects of what we do simply go unrecognised. Modern consumer products would not have developed nearly so quickly were it not for the myriad of new plastics, rubbers and microdevices that remain anonymous to non-scientists. Similarly, efforts within the industry to maximise usage of chemicals and minimise wastage are invisible outside of the industry. One further key area that has received little acknowledgment beyond the scope of its practitioners is the introduction of green chemistry, also known as environmentally benign chemistry. Green chemistry is defined by the American Chemical Society as the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The twelve principles of green chemistry embrace these aims, as well as those of waste prevention, the use of renewable raw materials, the minimisation of derivatives and better control of chemical processes. The Royal Society of Chemistry has established the Green Chemistry Network to promote green chemistry and now publishes a journal, Green Chemistry , devoted to the subject. Within green chemistry is the sub-domain of green analytical chemistry, in which the main principles are the elimination or reduction of the amounts of reagents and solvents during laboratory work, particularly at the sample preparation stage, according to a recent discussion. There has been good progress in this direction already, including the use of microextraction techniques such as microwave-assisted extraction and even the use of solventless techniques such as SPME and SPACE . Now, Norwegian researchers have advanced green analytical chemistry further by adapting the recently introduced technique of liquid-phase microextraction (LPME) for removing drugs and their metabolites from urine and plasma. With their modifications, the use of organic solvents was totally eliminated. In their place, plant oils were employed as extraction media in a green process. The technique was described in J. Sep. Sci. 2004, by Stig Pedersen-Bjergaard and Knut Einar Rasmussen from the Department of Pharmacy at the University of Oslo. In regular LPME, the porous walls of a hollow polypropylene fibre are impregnated with an organic solvent such as dihexyl ether, octanol or dodecyl acetate, then an extractant solution such as dilute formic acid is added to the fibre cavity. The fibre is immersed in a small volume of the sample, sometimes as little as 0.1 to 0.2 mL, and the analytes in the sample are drawn through the fibre and concentrate in the extractant. This technique has been used successfully to extract drugs from urine and plasma. Many samples can be extracted in parallel because the instrumentation is small and inexpensive, giving high throughput for the drug lab. So, even though a very small volume of organic solvent, typically 15 µL, is used in one fibre, the overall consumption becomes significant. The new technique tested four kinds of fatty oils that are normally used in foods (almond oil, arachis oil, olive oil and soybean oil) and four essential oils used in cosmetics, pharmaceuticals and nutrients (anise oil, fennel oil, lavender oil and peppermint oil). They were impregnated into the fibre in place of the organic solvents and tested with a panel of seven drugs. All of the essential oils proved compatible with human urine, but only anise oil worked with human plasma. However, the recoveries were comparable to those of the aforementioned organic solvents. Conversely, all of the fatty oils were compatible with urine and plasma, but their recoveries were lower, due to their higher viscosities. The fact that all of these oils are complex mixtures of many chemicals did not cause any problems. They did not leak significantly from the fibre membrane into the sample or the final formic acid solution, so their composition was not a factor. Excellent sample clean up was obtained. As a bonus, the extracted drugs were injected directly into a capillary electrophoresis apparatus for successful analysis using a phosphate buffer and UV detection, providing an organic solvent-free package of sample preparation and analysis. With optimisation, the researchers expect the technique to become acceptable in real lab situations. For all its environmental friendliness, it is unfortunate that this method and similar green initiatives will go unnoticed by the general public. Programmes like the Green Chemistry network may educate scientists and students but they fail to reach much beyond that. Related links:
Article by Steve Down |
"It's not easy being green"
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