Negative thermal ionization mass

WaIczyk T (1997) Iron isotope ratio measurements by negative thermal ionization mass spectrometry using FeF4" molecular ions. Int J Mass Spectrom Ion Proc 161 217-227... 

Wachsmann M, Heumann KG (1992) Negative thermal ionization mass spectrometry of main group elements, part 2. 6th group Sulfur, selenium, and tellurium. Int J Mass Spectrom Ion Proc 114 209-220... 

Volkening, J., Koppe, M., and Heumann, K. G. (1991) Tungsten isotope ratio determinations by negative thermal ionization mass spectrometry. International Journal of Mass Spectrometry and Ion Processes, 107, 361-368. 

A main characteristic of TIMS is that positively or negatively charged ions of the analyte are also formed and used for mass spectrometric analysis. In negative thermal ionization mass spectrometry (NTIMS) elements or molecules with a relatively high electron affinity (/iea > 2eV) can be... 

Anbar, A.D., Papanastassiou, D.A. and Wasserburg, G.J. (1997) Determination of iridium in natural waters by clean chemical extraction and negative thermal ionization mass spectrometry. Anal. Chem., 69, 2444—2450. 

Hemming, N.G., Hanson, G.N. 1994. A procedure for the isotopic analysis of boron by negative thermal ionization mass spectrometry. Chemical Geology 114 147-156. 

Vengosh, A. Chivas, A. R. McCulloch, M. T. Direct determination of boron and chlorine isotopes in geological materials by negative thermal-ionization mass spectrometry. Chem. Geol. 1989, 79, 333-343. 

Thermal-ionization mass spectrometers use a hot filament to ionize the sample. The element of interest is first purified using wet chemistry and then is loaded onto a source filament, often along with another substance that makes ionization easier and a more stable function of temperature. The filament is heated and as the sample evaporates, it is ionized. Both positive and negative ions can be created by thermal ionization, depending on the electronegativity of the element to be measured. Thermal-ionization mass spectrometers are used to measure a wide variety of elements, including magnesium, calcium, titanium, iron, nickel, rubidium, strontium, neodymium, samarium, rhenium, osmium, uranium, lead, and many others. 

The Re-Os decay system is discussed separately, in part because there are far fewer osmium isotope data than Sr-Nd-Pb data. This is true because, until —10 years ago, osmium isotopes in silicate rocks were extraordinarily difficult to measure. The advent of negative-ion thermal ionization mass spectrometry has decisively changed this (Greaser et al., 1991 Vblkening et al., 1991), and subsequently the number of publications providing osmium isotope data has increased dramatically. 

Garozzo, D., Giuffrida, M., and Montaudo, G., Primary Thermal Fragmentation in Poly(Lactic-Acid) Investigated by Positive and Negative Chemical Ionization Mass Spectrometry, Polym. Deg. Stab., 15,143,1986. 

Thermal ionization mass spectrometry (TIMS) has been the technique of choice in most lead and strontium isotope ratio studies. TIMS is a bulk technique, where samples are powdered and concentrated prior to analysis. This bulk technique has two negative features. First, processing of samples is time-consuming and requires additional laboratory equipment. Second, the samples must be homogeneous. This aspect of TIMS is problematic in samples where small-scale compositional vari-... 

Thermal electron attachment to SF6 has been studied in the ECD and NIMS at atmospheric pressure and in a chemical ionization mass spectrometer at lower pressures. From these data rate constants for thermal electron attachment and detachment to SF6, and the Qan values and electron affinities of SF6 and SF5 have been determined. The Morse potential energy curves for multiple negative-ion states were calculated using electron impact data and electron affinities. 

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