Purdue creates simpler alternative for chemical-analysis method

R. Graham Cooks (L) and Hao Chen
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Researchers have used the new method, called atmospheric-pressure thermal desorption ionization, to ionize various materials, including "organic salts," which play vital roles in biological processes.

"This is the first time researchers have done this at atmospheric pressure," said doctoral student Hao Chen.

Examples of organic salts include molecules such as proteins and lipids, which are critical for cell function. Scientists use mass spectrometry to learn about the composition of tissues and cells and in the field of proteomics, which requires identifying specific proteins and their proportions in biological samples such as blood.

Research findings regarding the new ionization technique are detailed in a paper now posted online and to appear in an upcoming issue of the European journal Angewandte Chemie. The paper was written by Chen, associate research scientist Zheng Ouyang and Cooks.

Mass spectrometry works by first turning molecules into ions — electrically charged versions of themselves — so that they can be detected and their masses can be measured. Conventional mass spectrometers analyze samples that are specially prepared and placed in a vacuum chamber.

The new "thermal ionization system" has been proven to be surprisingly accurate in revealing the masses of molecules in the materials being analyzed, Cooks said.

"We have shown that the spectrum is pretty clean and that there are almost no fragment ions, which was unexpected," Cooks said.

The researchers also used the method to ionize a material called an ionic liquid, which is like a "molten salt" at room temperature, Cooks said.

The ionic liquids are promising "green" alternatives to current solvents for industry and research because they are more environmentally friendly for making chemical compounds and can be easily