Sensitivity analysis accelerator mass spectrometry

Neutron activation also has been combined with accelerator mass spectrometry and has been demonstrated to have part-per-billion sensitivities fer bulk nitrogen analysis in silicon. This combination was also used to obtain depth profile of Cl in silicon semiconductors. ... 

C. Tuniz, Accelerator mass spectrometry ultra sensitive analysis for global science, Rad. Phys. Chem. 61, 317 322 (2001). 

Tuniz, C., Baird, J.R., Fink, D. Herzog, G.F. (1998) Accelerator Mass Spectrometry, Ultra Sensitive Analysis for Global Science. Boca Raton, FL CRC Press. 

Accelerator mass spectrometry (AMS) is an ultrasensitive analytical method for radioactivity analysis. AMS offers 10 -10 -fold increases in sensitivity over LSC or other decay counting methods so that levels as low as 0.0001 DPM can be detected (Brown et al., 2005, 2006). AMS has been applied to mass balance determination, pharmacokinetic studies of total radioactivity, and measurement of chemically modified DNA and proteins in humans after the administration of a low radioisotope dose (approximately lOnCi/person for mass balance and drug metabolism studies) (Buchholz et al., 1999 Garner, 2000 Garner et al., 2002 Liberman et al., 2004 White and Brown, 2004). In addition, off-line HPLC-AMS has been explored for metabolite profiling after... 

An important property of the MOT is the ability to catch atoms whose optical frequencies are shifted from the laser frequency by only a few natural linewidths. This property has been applied for ultrasensitive isotope trace analysis. Chen et al. (1999) developed the technique in order to detect a counted number of atoms of the radioactive isotopes Kr and Kr, with abundances 10 and 10 relative to the stable isotope Kr. The technique was called atom trap trace analysis (ATTA). At present, only the technique of accelerator mass spectrometry (AMS) has a detection sensitivity comparable to that of ATTA. Unlike the AMS technique based on a high-power cyclotron, the ATTA technique is much simpler and does not require a special operational environment. In the experiments by Chen et al. (1999), krypton gas was injected into a DC discharge volume, where the atoms were excited to a metastable level. 2D transverse laser cooling was used to collimate the atomic beam, and the Zee-man slowing technique was used to load the atoms into the MOT. With the specific laser frequency chosen for trapping the Kr or Kr isotope, only the chosen isotope could be trapped by the MOT. The experiment was able to detect a single trapped atom of an isotope, which remained in the MOT for about a second. 

Secondary ion mass spectrometry (SIMS) is a highly sensitive surface technique for characterizing materials. The procedure is based on the mass analysis of ions created when an impinging beam strikes the surface of a solid (or liquid, in a few special applications). The impinging ion beam, usually referred to as the primary ion beam, is generally accelerated to energies between 0.2 and 40 keV. Figure 4.1 shows the essential elements of SIMS. 

The ToF mass analyzer is the fastest, has a broad m/z range, is one of most sensitive mass spectrometry analyzers available, and is well-suited to imaging applications. In ToF mass analysis, gas-phase ions produced by a pulsed ion source are accelerated in a high vacuum by an electric field. After being accelerated, the ions enter a field-free region between the ion source and detector at a vdocily related to their m/z ratio, with lower-m/z ions reaching the detector earlier than higher-m/z ions. 

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