In Search of the Wild Molecule

We are swimming in a sea of molecules, unaware. That woman walking by has undiagnosed liver cancer, if we could only smell it. That student with a backpack is carrying explosives but who could tell? Those men working in that tunnel are being slowly poisoned by toxic gas, but who will warn them?

Purdue University researchers have developed a device that might open our collective eyes. The device is a miniature mass spectrometer, run on batteries. It has the potential for use at airport security, in hospital labs, and for environmental quality monitoring.

Researchers at Purdue University have shown how a new ultra-fast chemical-analysis tool has numerous promising uses for detecting everything from cancer in the liver to explosives residues on luggage and "biomarkers" in urine that provide an early warning for diseases.

The analytical chemists have most recently demonstrated how the technology, called desorption electrospray ionization, or DESI, rapidly detects the boundaries of cancerous tumors, information that could help ensure that surgeons remove the entire tumor.

"I wouldn't be surprised if pathologists are using this in operating rooms within two years," said R. Graham Cooks, the Henry Bohn Hass Distinguished Professor of Analytical Chemistry in Purdue's College of Science.

The technology has made it possible to speed up and simplify the use of a mass spectrometer, an analytical device that in its conventional form has been long established in modern laboratories. But while ordinary mass spectrometry is both time- and labor-intensive, the Purdue group has modified the technology to make it faster, more versatile and more portable.

.....A review paper about DESI and related techniques, which enable the direct chemical analysis of objects in an ordinary environment, will appear in the Friday (March 17) issue of the journal Science. The paper was written by Cooks, associate research scientist Zheng Ouyang, visiting scholar Zoltán Takáts and doctoral student Justin Wiseman, all in Purdue's Department of Chemistry. Several technical papers have been published about DESI experiments since the method was announced by the same laboratory in Science less than two years ago, but the new Science paper provides the first overall review of DESI and related techniques.

Mass spectrometry works by first turning molecules into ions, or electrically charged versions of themselves, which can be detected and analyzed.

"Having a charge enables you to not only detect molecules but also to measure their masses, which you can't do with neutral molecules," Cooks said.

Conventional mass spectrometers analyze samples that are specially prepared and placed in a vacuum chamber. The key DESI innovation is performing the ionization step in the air or directly on surfaces outside of the mass spectrometer's vacuum chamber.

In addition to DESI, Cooks' research group has designed and built a portable instrument that is roughly the size of a shoebox and weighs about 10 kilograms (22 pounds), compared to about 30 times that weight for a conventional mass spectrometer. The lightweight instrument can run on batteries, which means it can be carried anywhere....[it] promises to have applications in everything from airport security to medical diagnostics.

Read the rest here. Parallel research is going on at Oak Ridge National Lab.

Mass spectrometry has been around for several decades, but it is far more useful and powerful now. Soon, portable battery powered instruments will be used in the field, virtually anywhere.

Here is a brief primer on mass spectrometry. Here is a set of links to mass spectrometry resources, including tutorials.

Evolution gave us eyes, ears, noses, tongues, fingers, and other means of detecting and interpreting our environment. All sensory roads lead to the brain. The brain wants more information than our senses can give, thus the increasingly sophisticated analytical instruments and methods. The next step is a better brain.