Hars, G
1993
Mass Determination of Trapped Micro-Particles and Macro-Ions by Optical Techniques (and Subsequent Chemical Analysis by Laser Pyrolysis Mass Spectrometry)
Hars, G.; Arnold, N.S. and Meuzelaar H.L.C.
Proceedings of the 41st ASMS Conference on Mass Spectrometry and Allied Topics, San Francisco, CA, May 1993. Funded by US Army Research Office.
Extensive analytical interest in characterization of particulate matter extends in many applications to evaluation of individual micro-particles. For complete chemical characterization of individual microparticles adequate measurements of both particle physical characteristics (e.g., size, mass) and chemical constituents are required. Like molecular species, particles may also be readily ionized and manipulated by electrical techniques based on mass to charge ratios. An approach favored by the authors would provide an accurate mass determination that could be followed by laser pyrolysis (ionization) mass spectrometry to determine the chemical composition. Both measurements can be carried out in the same ion trap but they require different electrical operating conditions. For particle mass determination the ion trap operates as an Electrodynamic Balance (EDB) while the compositional analysis is performed in the Ion Trap Mass Spectrometer (ITMS) mode. For macro-ions and submicron particles the distinction between ions and charged particles may become blurred making it profitable to consider the ability to make mass measurements of individual submicroparticles based on optical detection techniques.
Chemical Characterization of Single Aerosol Particles Via Combined Electrodynamic Balance/Ion Trap Mass Spectrometry Techniques
Hars, G.; Arnold, N.S., Meuzelaar, H.L.C.
Proceedings of American Chemical Society Meeting, Chicago, IL, August 1993. Funded by US Army Research Office.
A multifunction Paul trap is described capable of trapping, stabilizing and analyzing electrostatically charged microparticles as well as a broad range of ions and macro-ions. Typically, particles in the 0.1-10 µm range are introduced by aerosolization from an aqueous suspension, although quasi-electrospray and dry powder type introduction methods can also be used. A new particle trajectory pattern, observed in the equatorial plane, was found to offer a nondestructive, optical method for determining the m/z value of microparticles and macro-ions, with a present accuracy of 1:103 and a potential maximum resolution of 1:106. Recent addition of a more powerful laser (Nd YAG, operating at 1.06 µm) has enabled us to generate laser fragmentation/ionization mass spectra of 1 µm dia polystyrene particles and of Bacillus subtilis spores. Current shot-to-shot reproducibility is still unsatisfactory and some as yet unresolved, mass calibration problems have been encountered. Nonetheless, the high intensity and apparent complex organic nature of the ion signals obtained might herald the emergence of a novel MS technique for chemical and physical characterization of single microorganisms and other components of respirable aerosols.
1992
Development of a Single Chamber EDB/ITMS System for Laser Pyrolysis MS Analysis of Individual Microparticles
Arnold, N.S.; Hars, G.; Cole, P.A. and Meuzelaar, H.L.C.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Ground, MD, November 1992. Funded by Army Research Office.
A novel technique for laser mass spectrometry of individual particles, e.g. microorganisms, is being developed. Present paper gives a detailed discussion on the theoretical and experimental aspects of trapping a submicron size charged particles pressures from atmospheric down to <10-7 torr. The ability to trap particles under UHV conditions has provided a new opportunity to study "ion trajectories" as they perform the solution of Mathieu equation.
Individual microparticles, mainly microorganisms, have been aerosolized and charged by a quasi-electrospray technique. A Paul type three-dimensional quadruple "trap" was constructed to combine the properties of an EDB (Electro-Dynamic Balance), capable of capturing the stabilizing micro-sized particles, with those of an ITMS (Ion Trap Mass Spectrometer), capable of trapping and mass selectivity detecting ionic species up to several thousand amu. A TEA CO2 laser (300 mJ per 200 µsec pulse) with focusing optics designed to produce a 50-80 µm beam waist through the center of the trap is used. A typical analysis cycle starts with the trap in EDB mode, thereby enabling capture and stabilization of one or more particles, followed by evacuation of the trap to high vacuum (<10-3 torr).
Hars, G
1993
Mass Determination of Trapped Micro-Particles and Macro-Ions by Optical Techniques (and Subsequent Chemical Analysis by Laser Pyrolysis Mass Spectrometry)
Hars, G.; Arnold, N.S. and Meuzelaar H.L.C.
Proceedings of the 41st ASMS Conference on Mass Spectrometry and Allied Topics, San Francisco, CA, May 1993. Funded by US Army Research Office.
Extensive analytical interest in characterization of particulate matter extends in many applications to evaluation of individual micro-particles. For complete chemical characterization of individual microparticles adequate measurements of both particle physical characteristics (e.g., size, mass) and chemical constituents are required. Like molecular species, particles may also be readily ionized and manipulated by electrical techniques based on mass to charge ratios. An approach favored by the authors would provide an accurate mass determination that could be followed by laser pyrolysis (ionization) mass spectrometry to determine the chemical composition. Both measurements can be carried out in the same ion trap but they require different electrical operating conditions. For particle mass determination the ion trap operates as an Electrodynamic Balance (EDB) while the compositional analysis is performed in the Ion Trap Mass Spectrometer (ITMS) mode. For macro-ions and submicron particles the distinction between ions and charged particles may become blurred making it profitable to consider the ability to make mass measurements of individual submicroparticles based on optical detection techniques.
Chemical Characterization of Single Aerosol Particles Via Combined Electrodynamic Balance/Ion Trap Mass Spectrometry Techniques
Hars, G.; Arnold, N.S., Meuzelaar, H.L.C.
Proceedings of American Chemical Society Meeting, Chicago, IL, August 1993. Funded by US Army Research Office.
A multifunction Paul trap is described capable of trapping, stabilizing and analyzing electrostatically charged microparticles as well as a broad range of ions and macro-ions. Typically, particles in the 0.1-10 µm range are introduced by aerosolization from an aqueous suspension, although quasi-electrospray and dry powder type introduction methods can also be used. A new particle trajectory pattern, observed in the equatorial plane, was found to offer a nondestructive, optical method for determining the m/z value of microparticles and macro-ions, with a present accuracy of 1:103 and a potential maximum resolution of 1:106. Recent addition of a more powerful laser (Nd YAG, operating at 1.06 µm) has enabled us to generate laser fragmentation/ionization mass spectra of 1 µm dia polystyrene particles and of Bacillus subtilis spores. Current shot-to-shot reproducibility is still unsatisfactory and some as yet unresolved, mass calibration problems have been encountered. Nonetheless, the high intensity and apparent complex organic nature of the ion signals obtained might herald the emergence of a novel MS technique for chemical and physical characterization of single microorganisms and other components of respirable aerosols.
1992
Development of a Single Chamber EDB/ITMS System for Laser Pyrolysis MS Analysis of Individual Microparticles
Arnold, N.S.; Hars, G.; Cole, P.A. and Meuzelaar, H.L.C.
US Army Chemical Research Development and Engineering Center Scientific Conference on Chemical Defense Research, Aberdeen Proving Ground, MD, November 1992. Funded by Army Research Office.
A novel technique for laser mass spectrometry of individual particles, e.g. microorganisms, is being developed. Present paper gives a detailed discussion on the theoretical and experimental aspects of trapping a submicron size charged particles pressures from atmospheric down to <10-7 torr. The ability to trap particles under UHV conditions has provided a new opportunity to study "ion trajectories" as they perform the solution of Mathieu equation.
Individual microparticles, mainly microorganisms, have been aerosolized and charged by a quasi-electrospray technique. A Paul type three-dimensional quadruple "trap" was constructed to combine the properties of an EDB (Electro-Dynamic Balance), capable of capturing the stabilizing micro-sized particles, with those of an ITMS (Ion Trap Mass Spectrometer), capable of trapping and mass selectivity detecting ionic species up to several thousand amu. A TEA CO2 laser (300 mJ per 200 µsec pulse) with focusing optics designed to produce a 50-80 µm beam waist through the center of the trap is used. A typical analysis cycle starts with the trap in EDB mode, thereby enabling capture and stabilization of one or more particles, followed by evacuation of the trap to high vacuum (<10-3 torr).