Gas, mass spectrometry

A focused laser beam of 0.2 joules per pulse is capable of releasing rare gases from well defined 10-100 pm size spots on a polished surface. As a result, it is possible to extend rare gas mass spectrometry to the region of less than 1 pg samples. The technique was first applied to the study of complex lunar samples by George Megrue [2]. 

Gillson GR, Douglas DJ, Fulford JE, Halligan KW, Tanner SD (1988) Nonspectroscopic interelement interferences in inductively coupled plasma mass spectrometry. Anal Chem 60 1472-1474 Gonfiantini R, Valkiers S, Taylor PDP, De Bievre P (1997) Adsorption in gas mass spectrometry. II Effects on the measurement of isotope amount ratios. Int J Mass Spectrom Ion Proc 171 231-242 Habfast K (1997) Advanced isotope ratio mass spectrometry. I magnetic isotope ratio mass spectrometers. In Modem Isotope Ratio Mass Spectrometry. Chemical Analysis Vol. 145. Platzner IT (ed). John Wiley and Sons, Chichester UK, p 11-82... 

Helium-3 is a decay product of radioactive tritium (3H, half-life = 12.44 years) that has been produced by nuclear bombs as well as naturally by cosmic rays in the upper atmosphere. Because virtually all 3He atoms escape from the surface ocean to the atmosphere, the 3He/tritium ratio in subsurface seawater samples indicates the time since the water s last exposure to the atmosphere. Both 3He and tritium are measured by gas mass spectrometry. Alternatively, tritium may be measured by gas counting with a detection limit of 0.05 to 0.08 tritium unit, where 1 tritium unit represents a 3H/H ratio of lxl0 18. A degassed water sample is sealed and stored for several months to allow the decay product 3He to accumulate in the container. The amount of 3He is then measured by mass spectrometry, yielding a detection limit of 0.001 to 0.003 tritium unit when 400-gram water samples are used. With this technique, the time since a water mass left the surface can be determined within a range from several months to 30 years. 

Mass-spectrometer date of the hydrogenated carbon nanotubes we have published in (Shulga et al. 2004). These nanotubes for the gas mass-spectrometry were synthesized by the electric-arc method using a nickel-yttrium catalyst. To remove amorphous carbon and the metal catalyst, the primary products containing 10-15 wt% of carbon SWNTs were purified by repeated oxidation in air at temperatures... 

Structure determination for new GAs. Mass spectrometry is a useful tool for identifying GAs whose structures have been previously determined, in which case comparison of mass spectra is sufficient. In contrast, the characterization of GAs of unknown structure is a much more difficult and time-consuming task. In these cases mass spectrometry can give information such as molecular weight and some indications of structure. 

Particle-Induced X-ray Emission, PIXE Nuclear Reaction Analysis, NRA Hydrogen Mass Spectrometry, HMS Noble Gas Mass Spectrometry, NGMS... 

The production rate of He is much higher than for any other cosmogenic nuclide. In minerals where it is quantitatively retained, He thus provides the chance to date exceptionally young surfaces. For example, we have derived an age of years for a sample from the 1993 lava flow of Lascar volcano (Chile) taken at 4540 m altitude a few months after eruption (Niedermann et al. 2001b), which illustrates the potential of He on timescales also relevant to archeological studies. New developments in noble gas mass spectrometry, such as the compressor ion source which improves the mass spectrometer sensitivity for He and Ne by two orders of magnitude (Baur 1999), may further increase the precision of He (as well as Ne) determinations in the future. 

The base pressure of the spectrometer system was 4x10 mbar and during the measurements 2-8x10 mbar. The purity of the vacuum system was steadily monitored by residual gas mass spectrometry (Quadrex 200, Leybold) to exclude artefacts. 

Variations in isotopic abundances that are caused by nuclear reactions induced by cosmic rays are most commonly utilized in cosmic ray exposure dating, but this employs isotopes that are measured by either accelerator or noble gas mass spectrometry [28, 29]. In fact, there are only a very limited number of elements that are suitable for the study of cosmogenic isotopic variations, which can be readily analyzed by either TIMS or MC-ICP-MS [28]. The most important application of these techniques are studies of the secondary neutron fluxes that are generated by (primary) cosmic rays. Such measurements aim to detect anomalies in Sm, Gd, and Cd isotopic abundances that are produced by (n,y) reactions, for example " Cd(n, y) Cd. Many of these investigations were conducted by TIMS [137-139], but some cosmogenic Cd isotope variations of lunar rocks and soUs were evaluated based on MC-ICP-MS isotope ratio data that were originally acquired as part of a stable isotope study [134]. 

Fig. 20. DSC-TGA data for HA PAA prepared using oxalic acid electrolyte and showing evolved gas Mass Spectrometry data for CO2.

Morelli et al used evolved gas mass spectrometry to carry out compositional analysis of ethylene-tetrafluoroethylene copolymers. The technique responded to the HF signal observed in the evolved gas analysis mass spectrum. 

Rube K., Kipphardt H. and Broekaert J. A. C. (2000) Determination of main and minor components of silicon-based materials by a combustion with elemental fluorine, separation of gaseous fluorination products by a carrier gas distillation, and gas mass spectrometry, Anal. Chem. 72 3875-3880. 

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