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A big step forward for mass spectrometers

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June 02, 1999 Share This!

RICHLAND, Wash. — Scientists at the William R. Wiley Environmental Molecular Sciences Laboratory in Richland, Wash., have developed a new tool that significantly improves the sensitivity of certain mass spectrometers.

The Wiley lab, a national user facility, is located at the Department of Energy's Pacific Northwest National Laboratory.

"Only a small fraction of the ions that are created for analysis are ever transmitted through the mass spectrometer and ultimately detected. This limits sensitivity and is a major problem. The Ion Funnel helps address this problem," said the device's inventor, Richard Smith, of Pacific Northwest

The device is known as the Electrodynamic Ion Funnel. It uses a series of conductive ring electrodes of increasingly smaller internal diameter to which radio frequency and direct current voltages are co-applied. This combination causes ions to be confined and more effectively focused and transmitted.

Mass spectrometry is a widely used tool in environmental, biotechnology, clinical and drug testing applications, as well as in medical, biological and other broad areas of scientific research. The use of mass spectrometry and its limitations are strongly affected by the sensitivity of the measurements that can be made, particularly in biological research. The Ion Funnel provides a huge gain in sensitivity for many forms of mass spectrometry.

Without the Ion Funnel, significant ion losses occur when ions pass from regions of high pressure to reach lower pressure regions where the actual mass spectrometer can function.

"Now, for the first time, using the Ion Funnel, large currents of ions can be focused in gases, allowing close to 100 percent efficiency in the transmission of ions to the mass analyzer. This results in an enormous gain in the sensitivity of the analyzer," said Smith.

A crucial attribute of the Ion Funnel concept is that the ion acceptance characteristics of the device are effectively decoupled from the ion emittance. This means that ion clouds of arbitrarily large size can be effectively focused as they are transported through the Ion Funnel, effectively reversing the normal ion cloud expansion that takes place due to the mutual repulsion of similarly charged ions. In short, a diffuse ion cloud can now be focused and transmitted through a relatively small exit aperture.

"The Ion Funnel serves to greatly increase ion transmission, particularly from higher pressure ion sources, such as those based on electrospray ionization that have become crucial to important areas of biological research. Forty-to 80-fold gains in sensitivity for ESI are routinely realized for conventional mass spectrometers retro-fitted with an Ion Funnel," said Smith.

"The Ion Funnel's capability for focusing significantly more ions into the mass spectrometer for analysis results in improved data collection, new applications and greater understanding of the substances analyzed," said Smith.

The Ion Funnel is expected to significantly extend the reach of biological assays. Advanced versions of the Ion Funnel are already being used in research funded by both the Department of Energy and the National Institute's of Health at Pacific Northwest. It has, for example, enabled the study of larger numbers of proteins from smaller biological samples. Potential applications of the Ion Funnel involve new ways to diagnose diseases, and research applications that will produce a greater understanding of the immune system, cellular signaling processes related to diseases such as cancer and environmental effects on health.

Tags: Energy, Fundamental Science, Mass Spectrometry and Separations

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