A couple of months ago, the water supply for the Town of Peterborough, NH, was found to contain unacceptable levels of E. coli bacteria. This unhappy discovery was made during a routine test; the word went out to boil all drinking and cooking water, and no one got sick. But how long had those bacteria been enjoying small-town hospitality? After all, water quality monitoring tends to be at regular intervals rather than on a continuous basis. Sandia researchers are working on a way to improve that picture.
Stephanie vL Henkel
The microChemLab, a handheld "chemistry laboratory," can analyze samples in both the liquid and the gaseous phases to detect toxins and harmful bacteria. Two underlying technologies are involved. The liquid prototype was developed at Sandia's Livermore lab and the gas phase design at the Albuquerque facility. The microChemLab, electronics, and sample collector weigh about 25 lb. and fit into a package the size of a small suitcase. The only external components are the water collectors.
The gaseous phase detector bubbles air through the water sample and collects trihalomethanes from the air. When the collector is heated, the trihalomethanes pass first through a separation column and then over a surface acoustic wave detector. At present the analyzer uses a 4–5 in. dia. commercial separation column, but the plan is to replace it with a 0.52 in. microfabricated version. Doing so will reduce power requirements and enhance performance, according to Curtis Mowry (photo), PI for the Albuquerque project.
Sandia researcher Curtis Mowry prepares to test tap water
Trihalomethanes are undesirable byproducts of the chlorination process in standard use for controlling the bacterial content of water. The microChemLab could be built into a process control loop that would help water utilities limit their initial formation.
The liquid phase detector operates on principles similar to those of the gaseous phase model. The primary difference is at the front end of the device, where separations into distinct bands are accomplished by microchannels coiled onto a glass chip about the diameter of a nickel. Proteins can be identified in a matter of seconds to minutes.
Contact Curtis Mowry, Sandia National Laboratories, Albuquerque, NM; 505-844-6271, [email protected]; or Jay West, Sandia National Laboratories, Livermore, CA; 925-294-3224, [email protected], www.sandia.gov.