Thermal ionization isotope dilution mass spectrometry

M. D. Schmitz, S. A. Bowring, and T. R. Ireland. Evaluation of Duluth Complex Anorthositic Series (AS3) Zircon as a U-Pb Geochronological Standard New High-Precision Isotope Dilution Thermal Ionization Mass Spectrometry Results, Geochim. Cosmochim. Acta, 67(2003) 3665-3672. 

Kelly WR, Fassett ID. 1983. Determination of picogram quantities of uranium in biological tissues by isotope-dilution thermal-ionization mass spectrometry with ion-counting detection. Anal Chem 55 1040-1044. 

A number of analytical techniques have been used to determine ppm to ppt levels of vanadium in biological materials. These include neutron activation analysis (NAA), graphite furnace atomic absorption spectrometry (GFAAS), spectrophotometry, isotope dilution thermal ionization-mass spectrometry (IDMS), and inductively coupled plasma atomic emission spectrometry (ICP-AES). Table 6-1 summarizes the analytical methods for determining vanadium in biological materials. 

Kelly et al. (NIST) describe an isotope dilution thermal ionization mass spectrometry method for the determination of sulfur in fossil fuels. The method is being used in NIST for certification of a number of liquid fuels at low sulfur concentration levels. Kelly et al. (NIST) also describe a designer calibration standard method for sulfur determination in fossil fuels for users to prepare NIST traceable working standards with known concentrations and uncertainties. 

Adriaens, A. G., Fassett, J. D., Kelly, W. R., Simons, D. S., and Adams, F. C. 1992. Determination of Uranium and Thorium Concentrations in Soils—Comparison of Isotope-Dilution Secondary Ion Mass-Spectrometry and Isotope-Dilution Thermal Ionization Mass-Spectrometry. Anal Chem 64(23), 2945-2950. 

Chartier, E, et al. (1999) Determination of erbium in nuclear fuels by isotope dilution thermal ionization mass spectrometry and glow discharge mass spectrometry. Journal of Analytical Atomic Spectrometry, 14, 1461-1465. 

Adriaens, A.G., Fasset, J.D., Kelly, W.R. et al. (1992). Determination of uranium and thorium concentrations in soils A comparison of isotope dilution-secondary ion mass spectrometry and isotope dilution-thermal ionization mass spectrometry, Anal. Chem. 64, 2945-2960. 

Table 1. Lead contamination blanks for serum collection, processing, and analysis by isotope dilution thermal ionization mass spectrometry in the WIGS Trace Metal/Mass Spectrometry facihty. University of California, Santa Cruz. Lead values are based upon repeated measurements.

Chartier, E, Aubert, M., and Pilier, M. (1999). Determination of Am and Cm in spent nuclear fuels by isotope dilution inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry after separation by high-performance liquid chromatography. Fresenius J.Anal. Chem. 364(4), 320. 

Pin,C.,Telouk,P.,and Imbert,]. L. (1995). Direct determination of the samarium Neodymium ratio in geological materials by inductively coupled plasma quadrupole mass spectrometry with cryogenic desolvation. Comparison with isotope dilution thermal ionization mass spectrometry.J. Anal. At. Spectrom. 10(2), 93. 

Thermal ionization mass spectrometry is an exceptionally valuable analytical tool. Its combination of high precision and high sensitivity makes it applicable in a wide variety of situations in which isotopic ratios are sought. In conjunction with isotope dilution, it provides quantitative analyses that are usually of higher quality than those yielded by any other method. 

The ideal internal standard is the same element as the analyte because it has similar mass, ionization energy, and chemical properties. Therefore, isotope dilution based calibration provides high accuracy as long as isotope equilibration is attained and the measured isotopes are free of spectral overlaps [192,193]. Standards do not need to be matrix-matched. Quadrupole-based ICP-MS instruments can typically provide isotope ratio precision of 0.1% to 0.5%. Much better isotope ratio precision can be obtained by using simultaneous MS detection, such as a multicollector-based instrument or perhaps time-of-flight MS. In comparison to thermal ionization mass spectrometry, ICP-MS provides much higher sample throughput and simpler, faster sample preparation. 

As mentioned, thermal ionization mass spectrometry is the area in which isotope dilution developed and in which it has received the widest range of applications. One of thermal ionization s major limitations is that it is essentially a single-element technique in no way can it be considered multielement in the sense that numerous elements can be assayed in a single analysis. It is thus highly desirable to mate isotope dilution with multielement analysis capability. Spark source mass spectrometry for years dominated elemental analysis, but the nature of the samples (solids) made use of isotope dilution difficult. Use of a multielement spike was reported as long ago as 1970 by Paulsen et al. [17], however, and more recently by Carter et al. [18] and by Jochum et al. [19,20]. 

Sample analysis by thermal ionization mass spectrometry (TIMS) results in measurement of isotopic ratios of minerals. Total mineral content of samples is then determined by one of two methods. One approach is to use flame atomic absorption spectrophotometry (AAS) to determine total mineral content of samples. Since AAS does not have the same level of precision as TIMS a sufficient number of replicates is analyzed for a mineral content determination with a CV of within 1%. Alternatively if a mineral has 3 or more isotopes and fractionation corrections are not made the following procedure may be used. An individual is fed one isotope and another isotope is added to the sample prior to analysis to determine the total mineral content of the sample by dilution of the second isotope. In this way both the amount of the isotope fed which is recovered in the feces and the total mineral content of the sample can be determined simultaneously. If fractionation corrections are to be made a mineral must have at least four isotopes. Details of these procedures will be reported separately. 

The most common method of determining the U-Pb date of an accessory mineral is the determination of uranium and lead isotopic abundances via isotope dilution and thermal ionization mass spectrometry (ID-TIMS). Most measurements in the 1970s and 1980s required that an aliquot of the dissolved mineral solution be made, with one portion being spiked with an enriched U and ° Pb tracer solution, and the... 

In cases which require extreme accuracy and precision, isotope dilution mass spectrometry (ID-MS) may be used to measure Pb concentrations. This consists of an addition to the sample of a solution of well-known Pb concentration and isotopic composition ( spike ) followed by determination of the isotopic composition of the spiked sample using mass spectrometry, Q-ICP-MS, ICP-SMS, multi-collector ICP-MS (MC-ICP-MS), or thermal ionization mass spectrometry (TIMS). 

Thermal ionization mass spectrometry (TIMS) is a sensitive mass spectrometric technique that has been deployed in some cases to measure trace amounts of uranium in urine and its isotopic composition (Kelly et al. 1987). The authors report measurement of one freeze-dried urine standard sample (SRM 2670) and two actual urine samples collected from children. For TIMS measurements, chemical separation has to be performed prior to the analysis. In an earlier work by the same author (Kelly and Fassett 1983), a spike of was used to implement isotope dilution measurements of picogram quantities of uranium in biological tissues. As mentioned earlier, a single urine sample tested by TIMS gave 3.4 ng L (Wrenn et al. 1992). 

Notes SEM, scanning electron microscope EDS, energy-dispersive sensor TEM, transmission electron microscr y SIMS, secondary ion mass spectrometry TIMS, thermal ionization mass spectrometry ICP-MS, inductively coupled plasma mass spectrometry XRF, x-ray fluorescence ID-MS, isotope dilution mass spectrometry XRD, x-ray diffraction GC-MS, gas chromatography-mass spectrometry. 

In the early days of mass spectrometry, research was focused on gas source isotope ratio mass spectrometry (IRMS) or thermal ionization mass spectrometry (TIMS), with as the main aim the determination of the isotopic composition and molar masses of the elements. Since the 1940s, isotope ratio measurements have also been used for the determination of isotope ratios involving a radiogenic nuclide and for quantitative element determination via isotope dilution (see also Chapter 8). The age of the solar system and the Earth were also of particular interest within isotope ratio science. With the establishment and improvement of TIMS instrumentation, the awareness of the importance of precision and accuracy and the need to be able to reproduce a result in another laboratory grew, while... 

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