BioEd Online

A handy-sized device promises chemists a portable kit that can detect the different compounds. Using a small but powerful magnet, it could one day aid doctors or give oil companies clues about where to drill.

For decades, a technique called nuclear magnetic resonance (NMR) has allowed scientists to investigate the chemical composition of materials. Molecules interact with a magnetic environment in different ways. So when a sample is placed in a uniform magnetic field, subtle perturbations allow scientists to deduce its chemical make-up.

But such a uniform field is found only inside a magnet, thus if the sample is large, the apparatus must be very large indeed. In hospitals, NMR forms the basis for magnetic resonance imaging, which gives doctors a non-invasive method of looking inside patients. With a sample the size of a person, the machines are often big enough to fill a small room.

Outside the box

Scientists have wanted to construct portable NMR devices for years, but they did not know how to create a uniform field without encircling the sample.

Now a team of German and US scientists have realized that they do not need such a field. "We're putting the sample outside the magnet," says Bernhard Blümich of Aachen University of Technology in Germany.

The trick involves a simple, permanent magnet about 20 to 50 times as strong as those that adorn refrigerators. Using about the same power as a standard light bulb, the device can discern the chemical properties of a material simply by registering the response of its atoms to applied magnetic fields.

To compensate for its imperfect magnetic field (which weakens as distance increases), the portable NMR machine matches it with a suitably shaped field of radio waves. This allows the field to tune itself to pick up how the molecules resonate.

Magnetic attractions

The researchers hope the technology will offer unusual medical opportunities. "In the clinics, the device could perhaps be used to follow the concentration of metabolic products and to do a chemical analysis of disease," Blümich speculates.

He also says that oil companies might use the technology to guide their search for fresh reserves many metres underground. "While you drill you want to know if you're drilling in the right direction," he says. The NMR device could give researchers in the field information about the chemicals in the soil and quality of the oil.