Nosing in on bad water: Geosmin detector

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  • Published: Sep 15, 2015
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Nosing in on bad water: Geosmin detector

e-Nose, you know?

An electronic

A bioelectronic "nose" that can detect the common contaminants of "off" water, namely geosmin and 2-methylisoborneol, has been developed to preclude the need for cumbersome and expensive gas chromatographic or mass spectrometric testing equipment. The same approach could also be used to detect drugs at airports, test food quality and develop new perfumes.

Manki Son, Dong-guk Cho, Jong Hyun Lim, Juhun Park, Seunghun Hong, Hwi Jin Ko, and Tai Hyun Park of Seoul National University, Korea, writing in the journal Biosensors and Bioelectronics screen olfactory sensors from the human nose to find the specific receptors that allow us to smell geosmin and 2-methylisoborneol formed in water when bacteria grow and then incorporated those receptors in a sensor system using nanovesicles characterised using ELS (electrophoretic light scattering) spectroscopy. The resulting device is easy to use and can detect tiny amounts of contamination in water far better than other detection methods, as low as 10 nanograms per litre of water, even in the presence of other potentially interfering molecules. The researchers report that their device can detect these compounds from real samples such as tap water, bottled water and river water without any pre-treatment processes.

The presence of bacteria in water can lead to health problems or simply make the water smell bad. Either way, no one wants to drink water with an off flavour out of choice. "Water that smells bad isn't necessarily toxic," explains Park. “But, if there's an off flavour, even if the water isn't toxic, you don't want to drink it. We wanted to develop a way to detect and remove this kind of contamination, so people are happy to drink water."

Water convention

Conventionally, water is tested for bacterial contamination by culturing any bacteria that might be present in a sample, in the laboratory. This obviously takes no short time. Alternatively, standard high-performance analytical techniques can be used to detect the odour molecules released by bacterial activity. Again, this can be time-consuming, complicated and is not amenable to real-time field testing of multiple samples. "These are good ways to detect smell molecules, but they require a large amount of work before the sample is even ready to test," says Park. "And, all of these tests need to be done in a laboratory with expensive equipment – they’re just not suitable for the field," he adds.

Earth, wine and water

Bacteria that commonly contaminate water produce characteristic odour molecules, among them the earthy and musty smells of geosmin (GSM, (4S,4aS,8aR)-4,8a-dimethyl-1,2,3,4,5,6,7,8-octahydronaphthalen-4a-ol), which is often associated with rain falling on earth after a dry spell and 2-methylisoborneol (MIB), also an odour of cork taint in wine.

The team hoped to find a much more straightforward, convenient and sensitive method that might be incorporated into a compact and portable device for on-site water testing. In addition to contamination of drinking water, bacteria and other microbes can also contaminate rivers and lakes, detecting such contamination sooner rather than later allows those controlling reservoirs and other bodies of water to take control before an algal bloom, for instance, gets out of hand.

"Our eventual goal is to develop a real human nose-like bioelectronic nose," explains Park. "In the human nose, there are about 400 different olfactory receptors. If we could develop our technology to include all of these, we would have a device that could smell anything we can, at lower concentrations."

The team points out that the same technology could have many applications in the food and drink industry, in perfume manufacture and perhaps even as a detector for metabolites present in a person's breath when they have specific diseases, such as cancer. There is a more fundamental side to the work too. "We don’t have a system for the classification of smell yet; it all still depends on our human sensory system. With our bioelectronic device, we can systematically detect and label smells, perhaps coming up with a universal smell code we can use to communicate in the future," Park says.

Related Links

Biosensors Bioelectronics 2015, 74, 199-206: "Real-time monitoring of geosmin and 2-methylisoborneol, representative odor compounds in water pollution using bioelectronic nose with human-like performance"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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