The biosensor is capable of detecting in food very small amounts of atrazine, one of the most widely used herbicides in agriculture and which also has very long lasting effects on environment. It is faster, more portable and cheaper than current laboratory methods which are used to detect contaminants, while having a very similar sensitivity. The system has been tested successfully to detect pesticides in samples of drinking water and commercial orange juice, as well as to detect traces of antibiotics in cow’s milk.
The agricultural use of atrazine, and other herbicides based on a chemical substance called triazine, often causes contamination both of underground water and surface water. Food safety agencies have established control measures to prevent these pesticides entering the food chain. Similarly, antibiotics used to treat bacterial infections in domestic animals may contaminate food and be harmful for people. The European Community has established upper limits for the presence of traces of pesticides and antibiotics in food, but the control of these limits is carried out in laboratories with expensive, slow and bulky equipment.
The sensor developed by scientists at the UAB and the CSIC will allow the detection of doses of atrazine at levels of 0.006 micrograms per litre, much lower than the maximum concentrations allowed by European regulations (0.1 micrograms per litre). It can do this more quickly and cheaply than laboratory chromatographs which are currently used in food safety laboratories. The sensor has a sensitivity to antibiotics of 1 microgram per litre for whole milk, while the legislation allows a maximum of 100 micrograms per litre.
Being portable, the technique can be used in situ for quantitative analysis of the presence of atrazine and other herbicides in food and water samples outside the laboratory. The sensor can be easily prepared by means of a process that can be extended on an industrial scale to allow the manufacture of large quantities at a very low cost, and may even be made for personal, disposable use.
The chemical mechanism to detect contaminants in a sample is similar to that used by the immune system to identify a virus or bacteria in the body. The organism attacks an infection by generating antibodies which hook onto, for example, a specific type of virus. Hence the virus is identified and may be eliminated.
In the case of the sensors, specific antibodies for atrazine and for are used. Once the antibodies hook onto the contaminating particles they are attracted to the surface of a transductor which converts the contact with the antibodies into electrical signals. By measuring these electric signals the device can determine the concentration of contaminants in the sample.