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Scientific Stimulus Produces Results

A cascade of opportunities are unleashed by one instrument, a novel idea, and EMSL's intramural program

A quiet, yet powerful process is at work at EMSL, providing a stimulus for science and innovation. The EMSL Research and Capability Development “Intramural” Program enables EMSL scientists to develop and demonstrate advanced capabilities that can become important parts of the EMSL user facility and highlight the types of new or advanced science that can be done with EMSL capabilities. With a combination of world-class instrumentation, innovation, novel adaptation of cutting-edge approaches, and timely investment, research produces amazing results at EMSL.

The Instrument

The instrument is DESI-MS, or Desorption ElectroSpray Ionization Mass Spectrometry. This technique, established at Purdue University in 2005, eliminates pretreatment steps and vacuum requirements for substrate-deposited samples to be analyzed using a mass spectrometer. Using DESI-MS, a sample is bombarded by a jet of charged droplets, which desorb and ionize analyte molecules that are then picked up by the mass spectrometer for analysis. This technique has been used and accepted in a broad range of fields, including forensics and pharmaceuticals. Acceptance in the environmental chemistry community has lagged, however.

nanoDESI photo

In 2007, several researchers urged EMSL to build a DESI instrument in order to offer its capabilities to a broad range of environmental applications. EMSL built such an instrument, and various studies have since used this technique to advantage. The first was a 2009 study of atmospheric chemistry to analyze ageing of organic aerosols that leads to formation of so-called “brown” carbon, and to understand the molecular reaction mechanism that turns white carbon into brown. One of DESI’s main advantages is the ability to analyze the same samples before and after the reaction. Researchers were able to identify the fundamental pathways that led to formation of brown carbon. The resulting paper was enthusiastically received by the chemical community and demonstrated that the DESI approach could be used on particles applied to substrate.

The Idea

Patrick Roach, a PNNL postdoctoral student, came to EMSL scientists with a novel idea to modify the DESI apparatus. Instead of collecting the signal in the normal way, he suggested that a second capillary be used, which acts as a pump to turn the aerosols dissolved in the deposited liquid into ions by nano-electrospray ionization. These ions are then analyzed in a high-resolution mass spectrometer. This creative modification enabled researchers to collect a high-quality signal in less time, making the analysis highly functional and very sensitive. In addition, Roach was able to teach undergraduate students to operate this modified apparatus in just a few hours, making the process highly practical as well. The new approach was dubbed “Nanospray DESI,” or nanoDESI.

According to Roach, "NanoDESI reduces the amount of material required for analysis, the time involved and, hence, the cost of obtaining data. Information from this technique provides insights that could help us understand the fundamental chemistry of atmospheric aerosols and other environmental samples."

EMSL researcher Alex Laskin, an analytical and physical aerosol chemist, says simply,“Pat’s invention is just plain elegant.”

The elegance of the technique is evidenced by the minimal amount of sample required—less than 10 nanograms—and a few minutes of time—coupled with its simplicity of use, which provides huge advantages for this technique.

Laskin has put nanoDESI through its paces many times. The fact that nanoDESI uses less sample, is time-efficient and easy to use, and has validated known results analyzed by other methods is more than enough reason to keep extending the possibilities of this unique apparatus.

The Research and Capability Development Program at EMSL

Laskin received funding for this research through EMSL’s Research and Capability Development program. His co-investigators—Julia Laskin, a PNNL physical chemist specializing in mass spectrometry, and Sergey Nizkorodov, a physical chemist specializing in molecular chemistry of organic aerosols from the University of California, Irvine—brought additional funding. The Research and Capability Development program provides a scientific funding stimulus to encourage EMSL scientists to demonstrate, through original research, the advanced capabilities of emerging techniques and instruments available at EMSL. This initial funding, coupled with the unique invention technique provided by Roach, has indeed created a cascade of research opportunities.

Laskin is excited about the possibilities for the future of this area of research.

“With two papers published and one on the way, we have an influx of new users who want to apply this technique for their research,” he said.

Studies focused on molecular chemistry of aerosols, such as those already published, are just the beginning. The research group also has plans to expand this technique to other areas of environmental science, such as analysis of crude oil, imaging mass spectrometry of microbial communities, and analysis of biological tissues.

The use of nanoDESI is just one example where EMSL’s capability development program is providing the stimulus to support novel approaches and new avenues of research, demonstrating EMSL’s unique broad range of capabilities for scientific research.

 

Additional Information: The Birth of nanoDESI; New Technique Provides Sensitive Analysis of Atmospheric Particles; Alex Laskin Bio; Purdue University DESI.

References: Laskin J, A Laskin, PJ Roach, GW Slysz, GA Anderson, SA Nizkorodov, DL Bones, LQ Nguyen. 2010. “High-Resolution Desorption Electrospray Ionization Mass Spectrometry for Chemical Characterization of Organic Aerosols” Analytical Chemistry. DOI: 10.1021/ac902801f. Roach P, J Laskin, A Laskin. 2010. “Nanospray desorption electrospray ionization: an ambient method for liquid-extraction surface sampling in mass spectrometry.” Analyst. DOI: 10.1039/C0AN00312C, Communication. Roach PJ, J Laskin, A Laskin. 2010. “Molecular Characterization of Organic Aerosols Using Nanospray-Desorption/Electrospray Ionization-Mass Spectrometry.” Analytical Chemistry. DOI: 10.1021/ac101449p.

PNNL-SA-75252

 

Released: October 14, 2010