Isotopic analysis by mass spectrometry

Isotopic Analysis by Thermal Ionization Mass Spectrometry 

Thermal ionization mass spectrometers (TIMS) with magnetic sector are thus the basic instruments for Pu and U isotopic analysis in safeguards inspection samples. The performance of commercial instruments has improved tremendously, particularly in the last 30 years, in terms of vacuum capability, design of the ionization source and detector assembly, stability of electrical supplies, sensitivity and linearity of ion current amplifiers, and includes full automatization of the measurement and data reduction. 

In modern instruments, the ionization source is equipped with a turret, which may hold 13 to MS filament assemblies (Tuttas et al. 1998). Each assembly carries one or two side filaments, usually in platinum or tungsten, and a center rhenium ionization filament. A 1 pi or less of sample solution containing 0.05 to 1 pg of uranium or 5-100 ng of plutonium is loaded onto a side filament, and dried electrically under controlled conditions to obtain a reproducible 

Various approaches have been devised to increase the thermoionization efficiency, such as electro-codeposition of actinides and platinum on the sample filament (Rokop et al. 1982), the resin bead loading technique (Walker and Smith 1979), or carburization (Jakopic et al. 2008). All these methods are said to facilitate the reduction of the sample species into atoms and enhance their ionization. An electrically heated cavity as sample holder installed in the source turret of a commercial mass spectrometer (Riciputi et al. 2002) yields also amazing increases of the ionization efficiency up to 5 and 7%. 

Typical scan over isotope ion peaks measured with compact discrete-dynode detectors 

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O Equations (15.4) andO (15.5) show that the deflections of the ions of the lighter isotope are greater than those of the heavier isotope, provided that their velocities and charges are the same. The isotope analysis by mass spectrometry and the electromagnetic isotope separation method using large-scale mass spectrometers, called Calutrons because of their early development at the University of California Cyclotron Laboratory, are based on these effects. 

C1457 standard test method for determination of total hydrogen content of uranium oxide powders and pellets by carrier gas extraction Uranium isotopic analysis by mass spectrometry... 

Boulyga, S.F. (2010) Caldum isotope analysis by mass spectrometry. Mass Spectrom. Rev., 29, 685—716. 

Cotte, J. F., Casabianca, H., Lheritier,J., Perrucchietti, C., Sanglar, C., Waton, FI., and Grenier-Laustalot, M. F. (2007). Study and validity of 13C stable carbon isotope ratio analysis by mass spectrometry and 2H site-specific natural isotopic fractionation by nuclear magnetic resonance isotopic measurements to characterize and control the authenticity of honey. Anal. Chim. Acta 582,125-136. 

The growing evidence (for example. References 36, 117, 118) that the hydrogenation of CO on various metals proceeds via the carbon formed by dissociative adsorption of CO led to the use of the hydrogen/deuterium isotope effect as one attempt to better define that the synthesis follows this reaction pathway. Another reason was to modify the mass of the hydrocarbon peaks so that interference from gases such as H2O, CO2, N2, etc., would not prevent analysis of products from transient isotope studies by mass spectrometry. However, the evidence from the early studies with H2/D2 led to conflicting viewpoints. Sakharoff and Dokukina obtained kjj/ku = 0.77 for a Co catalyst, whereas McKee reported a value of 2.2. 

Bowman MJ, Zaia J. Tags for the stable isotopic labeling of carbohydrates and quantitative analysis by mass spectrometry. Anal Chem 2007 79 5777-5784. 

The use of stable isotopes or tracers to study zinc absorption in humans with subsequent analysis by mass spectrometry has been reported in the literature. Analysis of fecal samples obtained 3 and 6 days after the administration of zinc-65 isotope in food showed that between 45% and 75% of zinc isotope was absorbed (Johnson 1982). The results indicated satisfactory detection of the zinc-67 isotope in human feces, while the zinc-70 isotope was not as detectable. Better precision and recovery were obtained for the zinc-67 isotope (2.4% CV >95% recovery) than for the zinc-70 isotope (38% CV 71% recovery). Sampie detection limits were not reported. Total reported sample preparation time was <2 hours, and it took only 5-10 minutes to anaiyze each sample on the mass spectrometer. 

Elemental analysis by mass spectrometry. A particular high-resolution mass spectrometer measures m z to an accuracy of 10 parts per million. This means that miz 100 can be measured to an accuracy of (100)(10 X 10 ) = 0.001 (and precision into the next decimal place). A molecular ion thought to be C4HnN3S or C4H11N3O2 was observed at m z 133.068 6. Compute the expected mass of each ion by adding the masses of the correct isotope of each atom and subtracting the mass of an electron. Which formula is correct ... 

It is often more advantageous to use comparative methods, that is, to work with the mixture of the two compounds in the experiments, which ensures identical experimental conditions for the parallel reactions. The isotope competition method does not require pure isotopic compounds, it can be used even with compounds of natural isotopic composition, and thus it can be applied to the determination of C, N, and 0 isotope effects. However, the isotopic composition must be measured with high accuracy, in the case of stable isotopes usually by mass spectrometry, in the case of radioisotopes by measuring the change in the specific activity. In order to obtain the kinetic isotope effect, one needs to determine the isotopic composition of the test compound, first at the start of the reaction then again after the reaction has taken place to a known extent. The isotope effect can also be obtained from the isotopic analysis of the reaction products. In the latter case, the method of the evaluation of k /k from the experimental data can be found, for example, in the book of Vertes and Kiss (1987). 

Isobar can be a source of positive bias in the determination of Pu isotopic abundance by mass spectrometry despite prior chemical separation of the two elements. In this respect, eluting Pu before U is advantageous (see section Isotopic Analysis by Thermal Ionization Mass Spectrometry, procedures (b)-(d)). Great attention must be placed anyway to minimize sources of blanks due to low levels of natural uranium in most chemical reagents and mass spectrometry filaments. It is therefore still customary to perform Pu measurement by alpha spectrometry in parallel with mass spectrometry. 

The application of isotope dilution analysis to ICP-MS-based hyphenated techniques, for example HPLC-ICP-MS, can be divided into two diflerent modes the spedes-unspecific mode and species-specific mode. The two modes are illustrated in Figure 4.6. Because IDA-ICP-MS relies on the measurement of isotope ratios by mass spectrometry, the traditional interference to the accuracy and precision of IDA should all be considered and some biases need further correction in this case, such as spectral interferences, dead time of detector, mass discrimination, and statistic and stability of ion counting. 

In this equation the red O signifies oxygen enriched in Its mass 18 isotope analysis of isotopic enrichment was performed by mass spectrometry... 

State-of-the-art TOF-SIMS instruments feature surface sensitivities well below one ppm of a mono layer, mass resolutions well above 10,000, mass accuracies in the ppm range, and lateral and depth resolutions below 100 nm and 1 nm, respectively. They can be applied to a wide variety of materials, all kinds of sample geometries, and to both conductors and insulators without requiring any sample preparation or pretreatment. TOF-SIMS combines high lateral and depth resolution with the extreme sensitivity and variety of information supplied by mass spectrometry (all elements, isotopes, molecules). This combination makes TOF-SIMS a unique technique for surface and thin film analysis, supplying information which is inaccessible by any other surface analytical technique, for example EDX, AES, or XPS. 

Merritt, D. A. and Hayes, J. M. (1994) Nitrogen isotopic analysis by isotope ratio monitoring gas chromatography mass spectrometry. Journal ofthe American Society ofMass Spectrometry 5,387 397. 

Zhou, H., Ranish, J.A., Watts, J.D., and Aebersold, R. (2002) Quantitative proteome analysis by solid-phase isotope tagging and mass spectrometry. Nat. Biotechnol. 20, 512-515. 

A. Deyhle. Improvements of Boron Isotope Analysis by Positive Thermal Ionization Mass Spectrometry Using Static Multicollection of CS2BO2 Ions. Int. J. Mass Spectrom., 206(2001) 79-89. 

AUTOMATED ANALYSIS OF STABLE ISOTOPES OFH, C, N, O AND S BY ISOTOPE RA TIO MASS SPECTROMETRY... 

R.S. Houk, Elemental and isotopic analysis by inductively coupled plasma mass spectrometry, Ace. Chem. Res., 27 (1994) 333-339. 

Dodson MH (1963) A theoretical study of the use of internal standards for precise isotopic analysis by the surface ionization technique Part I General first-order algebraic solutions. J Sci Instrum 40 289-295 Douglas DJ (1989) Some current perspectives on ICP-MS. Canad J Spectrosc 34 38-49 Douglas DJ, French JB (1986) An improved interface for inductively coupled plasma-mass spectrometry (ICP-MS). Spectrochim Acta 41B 197-204... 

Moriguti T, Nakamura E (1993) Precise lithium isotope analysis by thermal ionization mass spectrometry using lithium phosphate as an ion source. Proc Japan Acad Sci 69B 123-128 Moriguti T, Nakamura E (1998a) High-yield lithium separation and precise isotopic analysis for natural rock and aqueous samples. Chem Geol 145 91-104... 

Mason TFD, Weiss DJ, Horstwood M, Parrish RR, Russell SS, Mullane E, Coles BJ (2004b) High-precision Cu and Zn isotope analysis by plasma source mass spectrometry. Part 2. Correcting for mass discrimination effects. J Anal At Spectrom 19 218-226... 

Great care has to be taken in the analytical characterization of synthetic cyclic peptides.[73] The major side reactions during cyclization are epimerization of the C-terminal amino acid residue and cyclodimerization. Cyclodimers can be detected by mass spectrometry, although the analysis is not trivial, because artifacts do occur in some ionization techniques such as ES-MS as a result of aggregation.1 1 Ll 121 Real dimers can be detected as double-charged particles with mlz values identical to the cyclic monomers, but with a mass difference of 0.5 amu in the resolved isotope signals. The mass difference of the corresponding monomer is 1 amu. The cyclodimerization has received some attention as a direct method for the synthesis of C2-symmetrical cyclic peptides.[62 67 94113 115]... 

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