NEWS OF THE WEEK INSTRUMENTATION
NO FUSS, NO MUSS MASS SPEC New technique allows direct mass spectrometry at ambient conditions
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MAGINE DOING A MASS SPEC-
trometric analysis directly on your skin. With a new ionization method called desorption
C O M I N G UP R O S E S The new ionization method DESI can be used on samples such as this rose under ambient conditions with no sample preparation.
electrospray ionization (DESI), such an analysis could soon be possible on a routine basis.
In DESI, an ionized stream of solvent—produced by an electrospray source—is sprayed on the surface of a sample at ambient temperature. No prior sample preparation is needed. The solvent clusters in the beam act as projectiles, knocking ions from the sample, which are then propelled to the mass spectrometer through a hose {Science, 3 0 6 , 471 (2004)]. Thus, DESI takes sampling for mass spectrometry out of the vacuum chamber and moves it into the lab and, in principle, beyond. "The fact that you can examine material on ordinary surfaces —cloth, l e a t h e r without any preparation and do this in ambient air makes this a striking new method," says Purdue University chemistry professor R. Graham Cooks, who led
REMEDIATION
Radioactive Waste To Be Left In Tanks ongress has given the Department of Energy the go-ahead to leave some high-level radioactive waste in huge underground tanks at contaminated former nuclear weapons sites in South Carolina and Idaho. The provision, included in the defense authorization bill, redefines the radioactive tank sludge remaining after high-level radioactive liquid wastes are removed in those two states. The waste sludge need no longer be vitrified and buried in a repository, like high-level radioactive waste. DOE pushed for the provision after losing a court case when it proposed covering the waste in grout and leaving it in the tanks to speed cleanups and lower costs. Although small in volume, the sludge is highly radioactive, say opponents voicing concerns about groundwater contamination. When DOE lost in court to the
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Natural Resources Defense Council, which was supported by South Carolina, Washington state, and Idaho, the department turned to Congress to modify the Nuclear Waste Policy Act. In all, DOE oversees 100 million gal of radioactive waste in 250 underground tanks at DOE sites in Washington, South Carolina, Idaho, and New York. The provision does not apply to the largest tank location, DOE's Hanford Site in Washington, whose congressional delegation opposed the measure. South Carolina officials were split. The effort to modify the law was led by Sen. Lindsey Graham (R-S.C). Rep. John M. Spratt Jr. (D-S.C.) directed the opposition. Spratt added provisions requiring Nuclear Regulatory Commission oversight and a National Academy of Sciences study.-JEFF JOHNSON
the study Cooks predicts that the technique will be a "knockout winner" in forensic and public safety applications, including the analysis of dried blood, detection of explosives, and monitoring of chemical warfare agents. He also sees applications in drug metabolism studies and in two-dimensional surface analysis to locate the position of analytes in a sample matrixUsing an electrospray source to produce the ionized solvent that acts as the primary-ion beam is "a completely novel concept," says Renato Zenobi, an analytical chemistry professor at the Swiss Federal Institute of Technology, Zurich. 'Although the ultimate sensitivity and the mechanism for ion production are still being worked out, I believe this method will have great impact for the application of mass spectrometry to real-world samples." Cooks and his colleagues, including postdoctoral associate Zoltân Takâts, have taken mass spectra of a variety of compounds, ranging from the small, nonpolar lycopene in tomatoes to large, polar peptides and proteins. They have also shown that drug molecules can be measured on the surface of the skin. Although not necessary to obtain spectra, the solvent system— water or a water/methanol mixture —can be adjusted to optimize the signal for particular analytes. Changing the nature of the spray solution is simply like changing the reagent gas in a chemical ionization experiment, Cooks says. For example, they optimized detection of the explosive RDX by adding trifluoroacetic acid to the solvent. Cooks and his colleagues are moving forward on several fronts with the DESI technology They are doing experiments to understand the fundamental ionization mechanism. They also plan to couple DESI with the miniature mass spectrometer that Cooks has developed and start doing experiments outside the laboratory-CELIA HENRY HTTP://WWW.CEN-ONLINE.ORG
