As occurs all too often in scientific analysis, if you want to investigate more than one aspect of a sample, then you almost always need a different tool for each examination required. How convenient it would be if a substance could be both microscopically examined and chemically analyzed at the same time. In this vein, researchers from the Department of Energy’s (DOE's) Oak Ridge National Laboratory (ORNL) have created a hybrid optical microscope/mass spectrometry-based imaging system capable of observing and analyzing specimens simultaneously.

The promise of such a versatile instrument, according to the researchers, is that it can provide both exceptionally high-quality microscopic images along with spatially-resolved chemical analyses. This dual capability will help in the improvement of a range of disciplines and areas of study, such as chemical and biochemical science, drug development, and disease control.

"Knowing the chemical basis of material interactions that take place at interfaces is vital for designing and advancing new functional materials that are important for DOE missions such as organic photovoltaics for solar energy," said Dr. Gary Van Berkel of ORNL’s Chemical Sciences Division. "In addition, the new tool can be used to better understand the chemical basis of important biological processes such as drug transport, disease progression and response for treatment."

Unlike some specialized microscopes, ONRL's new device does not require a rigidly-controlled environment of sub-zero temperatures in which to operate. Instead, the hybrid optical microscope/mass spectrometry-based imaging system operates at room temperature and doesn't even require special pre-treatments of the samples fed into it. Yet, it is perfectly capable of imaging samples down to sub-micron resolution.

Included in the instrument are both bright-field and fluorescence microscopy capabilities that, when used in conjunction with scanning mass spectral imaging of tissue samples, revealed features as small as 15 μm in size distinguishable in both the mass spectral and optical images.

To provide material for mass-spectrometry, a UV laser ablation process (simply, the production of minute particles from a substance via the application of laser energy) removes tiny amounts of material to be analyzed from the sample and feeds that via a pumped stream of inert liquid that is then ionized in the mass spectrometer. The results are then displayed almost immediately on a computer monitor attached to the machine.

The resolution to less than one micron also provides the means to clearly identify and distinguish between polymers and the sub-components of similar-sized cells.

"Today’s mass spectrometry imaging techniques are not yet up to the task of reliably acquiring molecular information on a wide range of compound types," said Dr. John Cahill of ORNL. "Examples include synthetic polymers used in various functional materials like light harvesting and emitting devices or biopolymers like cellulose in plants or proteins in animal tissue."

The researchers believe that combining a hybrid optical microscope and an electrospray ionization system for mass-spectrometry may prove a breakthrough for laboratories in providing a relatively inexpensive, versatile machine that could accelerate processing times and free up resources.

The results of this research were recently published in the journal Analytical Chemistry.