You are here

Sensitive and Shape-Specific Molecular Identification


OBJECTIVE: The development of a compact and portable instrument that couples mass spectrometry and Rydberg spectroscopy to provide a complete"fingerprint"of a molecule, including molecular mass as well as isomeric and conformeric identification. This instrument will enable a major increase in selectivity for threat identification in the field, while minimizing sample consumption, as well as instrument footprint and cost. DESCRIPTION: Mass spectrometers (MS) are powerful and widely used tools for molecular analysis in chemical and pharmaceutical industries, for environmental analysis, in forensic labs, and in basic research. However, the standard instruments have two primary drawbacks for application in-the-field 1) inability to rapidly identify isomers and conformers of molecules of interest and 2) its size; they are often large cumbersome instruments. In recent years it has been shown that excited electronic (Rydberg) states could distinguish among molecular shapes (isomers) for several different atomic compositions. Laser-induced Rydberg spectra could provide"fingerprints"that, when joined with MS molecular mass spectra, would enable unambiguous identification of molecular structures (isomers) and, further, different molecular shapes (conformers) of the same isomer. Recent advances in MS have also lead to reduction in instrument footprint size. This call seeks to push the limits of MS miniaturization while simultaneously coupling it to Rydberg Spectroscopy, resulting in a compact, self-contained unit for increased discrimination of chemical and biological threats PHASE I: (Feasibility Study) Demonstrate coincident measurement of mass spectra and Rydberg ionization for a set of molecular isomers. Demonstrate design for two-dimensional coincidence Rydberg and mass spectra for complete signature fingerprint. Develop designs for miniaturized Rydberg/MS detectors. Design criteria must include: simplicity and minimum number of parts, ruggedness and sensitivity. Provide cost estimate for instrument. PHASE II: (Prototype Delivery) Build prototype Rydberg/MS detection unit using designs from Phase I. Demonstrate coincidence operation for isomer identification. Provide validation data on maximum mass range. Determine sensitivity of instrument and ability to identify threat agents against a large background of volatile organic compounds. PHASE III DUAL USE APPLICATIONS: The miniaturization of mass spectrometry coupled to Rydberg spectroscopy is an attractive concept for an advanced chemical/biological sensor which can identify and distinguish between isomeric forms of the same compound. This phase of the project will couple mass spectrometry to Rydberg spectroscopy. The impact of this work would provide modern labs with the ultimate analytical tool for rapid, unambiguous identification of any analyte, from environmental toxins to biologically active pharmaceuticals and beyond. Consequently the commercial potential of the end product would be enormous, rivaling NMR and current tandem mass spectroscopic techniques, which are expensive, cumbersome and lack sensitivity. REFERENCES: 1. Gosselin and Weber,"Rydberg Fingerprint Spectroscopy: A New Spectroscopic Tool with Local and Global Structural Sensitivity", J. Phys. Chem. A 2005, 109, 4899-4904 2. Cardoza, Rudakov, Fedor, Hansen, and Weber,"Identification of Isomeric Hydrocarbons by Rydberg Photoelectron Spectroscopy", Journal of Electron Spectroscopy and Related Phenomena 2008, 165, 5 - 10. 3. Minnitti and Weber,"Time-Resolved Conformational Dynamics in Hydrocarbon Chains", Physical Review Letters 2007, 98, 253004. 4. Kuthirummal and Weber,"Structure Sensitive Photoionization via Rydberg Levels", Journal of Molecular Structure 2006, 787, 163 - 166.
US Flag An Official Website of the United States Government