TOXICOLOGY

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Electronic Nose Sniffs Out Toxins

Imagine a polka-dotted postage stamp-sized sensor that can sniff out some known poisonous gases and toxins and show the results simply by changing colors. Support for the development and application of this electronic nose comes from the National Institute of Environmental Health Sciences, part of the National Institutes of Health. The new technology is discussed in the September issue of Nature Chemistry and exemplifies the types of sensors that are being developed as part of the NIH Genes, Environment and Health Initiative (GEI) (http://www.gei.nih.gov/index.asp). Once fully developed, the sensor could be useful in detecting high exposures to toxic industrial chemicals that pose serious health risks in the workplace or through accidental exposure. While physicists have radiation badges to protect them in the workplace, chemists and workers who handle chemicals do not have equivalent devices to monitor their exposure to potentially toxic chemicals. The investigators have created what they refer to as an optoelectronic nose, an artificial nose for the detection of toxic industrial chemicals (TICs) that is simple, fast, inexpensive, and works by visualizing colors, and hope to be able to market the wearable sensor within a few years. The device has a disposable 36-dye sensor array that changes colors when exposed to different chemicals. The pattern of the color change is a unique molecular fingerprint for any toxic gas and also tells its concentration. By comparing that pattern to a library of color fingerprints, the device can identify and quantify the TICs in a matter of seconds. Older detection methods have relied on sensors whose response originates from weak and highly non-specific chemical interactions, whereas this new technology is more responsive to a diverse set of chemicals. The power of this sensor to identify so many volatile toxins stems from the increased range of interactions that are used to discriminate the response of the array. To test the application of their color sensor array, the study chose 19 representative examples of toxic industrial chemicals. Chemicals such as ammonia, chlorine, nitric acid and sulfur dioxide at concentrations known to be immediately dangerous to life or health were included. The arrays were exposed to the chemicals for two minutes. Most of the chemicals were identified from the array color change in a number of seconds and almost 90% of them were detected within two minutes. The laboratory studies used inexpensive flatbed scanners for imaging, but a fully functional prototype handheld device has been developed that uses inexpensive white LED illumination and an ordinary camera, which will make the whole process of scanning more sensitive, smaller, faster, and even less expensive. It will be similar to a card scanning device. One of the nice things about this technology is that it uses components that are readily available and relatively inexpensive. Given the broad range of chemicals that can be detected and the high sensitivity of the array to those compounds, it appears that this device will be particularly useful in occupational settings. Here is a link to photo of a postage stamp sized optical sensor array (small square silver colored device) for toxic gases and the sampled color changes associated with a few representative poison gases (chlorine, fluorine, hydrofluoric acid, hydrogen cyanide, B2H2, hydrazine, cobalt chloride, H2S, phosphine, ammonia, NO2, and sulphur dioxide).

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