At Oak Ridge National Laboratory (ORNL), a Department of Energy (DOE) facility, researchers have been involved with mass spectrometry since the mid-1940s, and today they continue to refine the technique for sorting molecules according to mass and charge. Their work addresses such problems as detection of trace chemicals from explosives and detection of pollutants in flue gases, soils and solid wastes. It has expanded from analysis of lightweight, volatile molecules to the probing of bulky biological molecules such as proteins and DNA.
In recent years, scientists at ORNL and elsewhere began combining lasers with mass spectrometers, creating a research tool more powerful than F.W. Aston of Cambridge University could have imagined when he developed the mass spectrometer in 1919. The latest techniques allow them to explore new ways to detect and structurally analyze small quantities of heavier biological molecules - such as DNA and proteins - with greater resolution.
"With these advances, mass spectrometry is emerging as a standout among tools for analyzing complex biological molecules," said Marvin Poutsma, director of the Chemical and Analytical Sciences Division.
ORNL, a world-class center for mass spectrometry, is involved in an array of projects, some of which were featured in a special edition of Rapid Communications in Mass Spectrometry, an international journal devoted to the latest in the field. A total of 23 papers involving 33 ORNL staff scientists were published in the issue devoted exclusively to work at ORNL.
In addition to fundamental studies, projects at ORNL include work in the areas of explosive detection, environmental monitoring, biomedical research and national security/nuclear non-proliferation. Using mass spectrometry, researchers can detect in the air trace constituents of explosives. Similar techniques allow them to examine pollutants in flue gases while still other techniques allow researchers to gather valuable information about geological history by looking at stable isotope ratios in soil/mineral samples. They can learn much about how and when minerals were deposited. They can also gain valuable information about petroleum deposits and underground water supplies.
In areas related to health, researchers use mass spectrometry to identify a segment of DNA that is specific for the bacterium that causes Legionnaire's disease. And ORNL researchers have also developed a method that may prove useful for screening individuals for cystic fibrosis.
Many of the successes at ORNL have resulted from researchers' efforts to improve existing techniques while others have involved innovation. ORNL researchers have pioneered new methods for ionization, which is a necessary first step in mass spectrometry. Ionization involves converting the sample from its form as a solid, liquid or gas to a gas-phase ion. Latest ionization methods outlined in ORNL research papers are electrospray of solutions, laser manipulation of complex molecules and solids, positron bombardment of gases and ion sputtering of insulator solids.
The next step in mass spectrometry involves separating these ions according to their characteristic mass-to-charge ratios. Methods used at ORNL involve quadrupole ion trap mass spectrometry and Fourier Transform ion cyclotron resonance mass spectrometry.
ORNL researchers employ other methods to gain additional structural information by causing the ions to undergo selective chemical reactions in the gas phase between the time of their formation and detection.
While mass spectrometry involves high-precision science practiced by a relatively few highly trained scientists, its benefits are far-reaching. ORNL's diverse staff has shared in a number of successes involving numerous projects. A recent emphasis is the development of portable instruments to allow for in-field detection of ultratrace components in the environment.
"ORNL's contributions have covered the entire spectrum, from fundamental research through design, construction and field testing of a prototype instrument, generating along the way a number of licensed inventions," Poutsma said.
ORNL, one of DOE's multiprogram research facilities, is managed by Lockheed Martin Energy Research Corporation.