Sniffing out chloride

When industrial plants are wrecked, they often leave behind a site with contaminated soil. If it was a metalworking plant, a textile production or dry-cleaning facility, a paint manufacturing or an animal waste processing plant, the soil is often contaminated with chlorine-based solvents.,

In order to bring the concentration back down to below the legally prescribed levels, remediation companies are making increasing use of sophisticated processes that work with bacteria. Without having to dig up the site, specialized strains are used to digest even the most toxic halogenated organic compounds, converting them into harmless chloride, water and carbon dioxide. Many types of bacteria can be isolated from normal soil samples. The capability of such organisms correlates with the rate of chloride released. Scientists in Stuttgart have constructed a test instrument that processes a large number of samples automatically. It is equally suitable for medical and pharmaceutical applications or the monitoring of pure water supplies. It is highly sensitive - even with low-volume samples.
The device is being used at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB to search for environmentally more compatible enzymatic synthesis steps in which chloride is bound or released. The electrochemical sensor that we have been working on together with the company Haaf Mess-Regeltechnik is capable of detecting chloride concentrations down to ten micromols per litre in a sample of only one fiftieth of a milliliter, reports Dr. Christiane Buta. This is equivalent to the concentration of one gram of domestic salt in nearly two cubic meters of water. There is a similar electrode being sensitive to the chemically related bromide - and it would be quite conceivable to construct sensors for fluoride and iodide on the same principle.
Colleagues at the associated Fraunhofer Institute for Manufacturing Engineering and Automation IPA have integrated the sensors in a pipette feeder robot. The machine extracts four samples simultaneously and injects them into test loops, explains Stefan Wössner. From there they are fed to the test cell equipped with the sensors. The software records the measured values and controls at the same time the intake of the next samples. In this way, a standard microtitration plate containing 96 samples can be processed in only nine minutes. When performed manually, the same process takes much longer. In the present setup, up to 16 such plates can be introduced simultaneously and analyzed by the machine.,For further information:,Dr. Christiane Buta ,Telefon +49/ 7 11 / 9 70-41 45 ,Fax +49/ 7 11 / 9 70-42 00 ,[e-mail]
Dipl.-Phys. Stefan Wo?ner ,Telefon +49/ 7 11 / 9 70-12 34 ,Fax +49/ 7 11 / 9 70-10 05 ,[e-mail]

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