Chemicals accelerator mass spectrometry

DGE a AC AMS APCI API AP-MALDI APPI ASAP BIRD c CAD CE CF CF-FAB Cl CID cw CZE Da DAPCI DART DC DE DESI DIOS DTIMS EC ECD El ELDI EM ESI ETD eV f FAB FAIMS FD FI FT FTICR two-dimensional gel electrophoresis atto, 10 18 alternating current accelerator mass spectrometry atmospheric pressure chemical ionization atmospheric pressure ionization atmospheric pressure matrix-assisted laser desorption/ionization atmospheric pressure photoionization atmospheric-pressure solids analysis probe blackbody infrared radiative dissociation centi, 10-2 collision-activated dissociation capillary electrophoresis continuous flow continuous flow fast atom bombardment chemical ionization collision-induced dissociation continuous wave capillary zone electrophoresis dalton desorption atmospheric pressure chemical ionization direct analysis in real time direct current delayed extraction desorption electrospray ionization desorption/ionization on silicon drift tube ion mobility spectrometry electrochromatography electron capture dissociation electron ionization electrospray-assisted laser desorption/ionization electron multiplier electrospray ionization electron transfer dissociation electron volt femto, 1CT15 fast atom bombardment field asymmetric waveform ion mobility spectrometry field desorption field ionization Fourier transform Fourier transform ion cyclotron resonance... 

In order to provide AMS analyses to the broad ocean sciences research community, the National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) was established at Woods Hole Oceanographic Institution (Massachusetts) in 1989. Studies performed there include identification of sources of carbon-bearing materials in the water column and sediment, dating of sedimentary samples, investigations of paleocirculation patterns (e.g., from observations of differences in 14C relative abundances in planktonic and benthic foraminifera, and coral cores and cross sections), as well as studies of modern oceanic carbon cycling and circulation. In fact, much that is known about advective and diffusive processes in the ocean comes from measurements of chemical tracers, such as 14C, rather than from direct measurements of water mass flow. 

XPS will aid in understanding specifically the surface of the black deposit covering pictographs in Little Lost River Cave in Idaho. This work will complement other bulk analyses carried out with pyrolysis-GC-MS and thermally assisted hydrolysis /methylation (THM)-GC-MS (75). The objectives of this project were to use XPS to qualitatively determine the surface elemental composition of the black residue semiquantitatively characterize the surface, for comparison with other surface-related materials and examine the relationship between the chemistry and depth by using Ar+ sputtering. This, then, will aid in validating the radiocarbon date obtained through plasma-chemical oxidation and accelerator mass spectrometry by Steelman et al. (5). 

The ratio of a sample is measured in relation to a standard to improve the accuracy and precision of accelerator mass spectrometry measurements (Elmore and Phillips, 1987). Multiplying the ratio by 1000 results in the delta (del) values having units of parts per thousand, also know as per mil (%o). For standards, it is necessary to use wood from trees harvested before about 1850 pre-industrial, to avoid the Suess effects. The standard value for pre-industrialized atmospheric CO2 is 13.56 dpm g-1 or 14C/C equals 1.176 x 10-12 (Broecker and Peng, 1982). A correction term involving the effects of isotopic fractionation (IF) are also subtracted out of this equation. Isotopes are fractionated due to physical and chemical reactions (more details in the following section), thereby making the abundance of carbon isotopes (12C, 13C, and 14C) different in plants (Faure, 1986). The National Bureau of Standards currently provides an oxalic acid 14C standard that is used for this correction however, there have been many problems associated with development of this standard (Craig, 1954, 1961 Stuiver and Polach, 1977). 

Chemical separations may be specific for the analyte of interest (see Chapter 3), such as liquid or gas chromatography, or scavenging (such as by precipitation) to remove the major interfering substances. Addition of carrier, as practiced in radioanalytical chemistry to assist in purifying radionuclides, usually is not appropriate for mass spectrometric analysis. Such addition undermines the isotopic ratio measurements that are often at the heart of this procedure, and also overloads the system for ion generation and peak resolution (but carrier addition is used for accelerator mass spectrometry). Addition of tracers, known as isotope dilution, is often employed for yield determination (see Section 17.2.9). Interferences are distinctly different in radiometric and MS analyses of radionuclides, and may be the deciding factor in selecting one method versus the other. 

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... 

Other experiments have also aimed to identify the chemical structure of potential ochratoxin A adducts. In in vitro studies, incubation of ochratoxin A with DNA or dG in the presence of various activation systems did not reveal any adducts, neither by P-postlabelling nor by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Subsequently, DNA was isolated from the livers and kidneys of male Fischer rats treated with a single dose of P C]ochratoxin A (0.5 mg/kg bw) and analysed by C-accelerated mass spectrometry. No significant difference between control group and treated group could be observed in C activity in isolated DNA from treated animals, and no specific ochratoxin A-DNA adducts were detected with C-accelerated mass spectrometry (Mally et al., 2004). The EFSA opinion pointed out that a concern in the interpretation of these results is that DNA adducts may have been repaired, as DNA was isolated 72 h after a single treatment with a relatively low dose, which is in contrast to other studies, in which DNA was isolated within 24 h after exposure to ochratoxin A (European Food Safety Authority, 2006),... 

The book concentrates on the most common instruments nsed in chemical, environmental, biological, and medical research. Less frequently encountered forms of mass spectrometry are not addressed, such as inductively coupled plasma mass spectrometry (ICP-MS) isotope ratio mass spectrometry (IRMS), accelerator mass spectrometry (AMS), proton transfer reaction mass spectrometry (PTRMS), and single-particle laser ablation time-of-flight mass spectrometry (SPLAT). 

Accelerator mass spectrometry (AMS) has long been used for quantifying concentrations of metabolites in humans, primarily for activated metabolites of environmental compounds that form genotoxic macromolecular adducts (Turteltaub et al., 1993, 1997, 1999 Dingley et al., 1999 Mauthe et al., 1999 Lightfoot et al., 2000 Cupid et al., 2004) agrieultaural chemicals that chronically... 

K. W. (1998) Attomole detection of 3H in biological samples using accelerator mass spectrometry application in low-dose, dual-isotope tracer studies in conjunction with 14C accelerator mass spectrometry. Chemical Research in Toxicology, 11 (VS), 1217-1222. 

Chiarappa-Zucca, M.L., Finkel, R.C., Martinelli, R.E., McAninch, IE., Nelson, D.O., liirteltaub, K.W. (2004) Measurement of beryllium in biological samples by accelerator mass spectrometry applications for studying chronic beryllium disease. Chemical Research in Toxicology, 17(12), 1614-1620. 

Trace levels of inorganic chemical species, e.g. lead, arsenic, cadmium, are aiso monitored in food stuffs, often using ICP-MS. The advantage of MS over AAS is that severai eiements may be measured simultaneously and the concentrations of individual isotopes may be measured, facilitating metabolism/ nutrient studies with stable isotope materials. Precise determination of isotope ratios (e.g. C, N and O) by IRMS is also important in agricultural and food authenticity studies. Accelerator mass spectrometry is used in tracer studies, for the determination of extremely low levels of carbon-14 (and other) isotopes. 

G.C. Mattem, C.I. Nuessle, D.L. Green, W.M. Leimkuehler, J.D. Philpot, RJ. Ness, and K.S. Billesbach, Accelerated field residue analysis of tebuconazole using Soxtec extraction and HPLC/electrospray tandem mass spectrometry (HPLC/ESI-MS-MS), Presented at the Midwest Regional Meeting of the American Chemical Society, Osage Beach, MO, October 29, 1997. 

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