Isotope ratio applications

TIMS, depending on the application [3]. These developments with magnetic sector instruments include multiple Faraday cup detectors (multicollectors) and multiple ion counters. The Faraday cup multicollectors have enabled the determination of isotope ratios with accuracy and precision rivaling TIMS [4], Due to lower sensitivity and differences in instrument design, quadrupole instruments (quadrupole inductively coupled plasma mass spectrometry [Q-ICP-MS]) have not demonstrated the same accuracy and precision as magnetic sector instruments, especially at low concentrations [5], Nevertheless, improvements in the sensitivity of quadrupole instrumentation have also increased their utility for many isotope ratio applications [6]. 

In spite of these issues, based on the higher availability of MC-ICPMS instrumentation in more laboratories and the high discriminating potential of isotopic analysis, a wider use of LA-ICPMS-based isotope ratio applications in archaeometric research can be anticipated. 

I 7 Quality Control in Isotope Ratio Applications Repeatability condition of measurement... 

Increases in mass resolution are not only accortpanied by a loss in ion transmission efficiency and hence signal intensity (Figure 2.15), but also by a change in peak shape from flat topped to triangular (Figure 2.14(b)).Moreover, the extremely narrow peaks at high mass resolution require an absolutely stable mass calibration (especially for isotope ratio applications). 

The previous discussion demonstrates that measurement of precise isotope ratios requires a substantial amount of operator experience, particularly with samples that have not been examined previously. A choice of filament metal must be made, the preparation of the sample on the filament surface is important (particularly when activators are used), and the rate of evaporation (and therefore temperature control) may be crucial. Despite these challenges, this method of surface ionization is a useful technique for measuring precise isotope ratios for multiple isotopes. Other chapters in this book discuss practical details and applications. 

Accurate, precise isotope ratio measurements are important in a wide variety of applications, including dating, examination of environmental samples, and studies on drug metabolism. The degree of accuracy and precision required necessitates the use of special isotope mass spectrometers, which mostly use thermal ionization or inductively coupled plasma ionization, often together with multiple ion collectors. 

Accurate, precise isotope ratio measurements are used in a variety of applications including dating of artifacts or rocks, studies on drug metabolism, and investigations of environmental issues. Special mass spectrometers are needed for such accuracy and precision. 

Figure 10.4 shows a schematic representation of the multidimensional GC-IRMS System developed by Nitz et al. (27). The performance of this system is demonstrated with an application from the field of flavour analysis. A Siemens SiChromat 2-8 double-oven gas chromatograph equipped with two FIDs, a live-T switching device and two capillary columns was coupled on-line with a triple-collector (masses 44,45 and 46) isotope ratio mass spectrometer via a high efficiency combustion furnace. The column eluate could be directed either to FID3 or to the MS by means of a modified Deans switching system . 

Farquhar, G.D., Hubick, K.T., Condon, A.G. Richards, R.A. (1988). Carbon isotope fractionation and plant water-use efficiency. In Applications of Stable Isotope Ratios to Ecological Research, ed. P.W. Rundel, J.R. Ehleringer K.A. Nagy, pp.21 0. New York Springer-Verlag. 

Horn I, Rudnick RL, McDonongh WF (2000) Precise elemental and isotope ratio determination by simultaneous solution nebnlization and laser ablation-ICP-MS Application to U-Pb geochronology. ChemGeol 164 281-301... 

Applications Sector instruments are applied for niche applications such as high-resolution measurements and fundamental ion chemistry studies. Magnetic sector mass spectrometers remain the instrument of choice in areas of target compound trace analysis, accurate mass measurement and isotope ratio measurement. 

Table 8.62 shows the main characteristics of ICP-MS, which is widely used in routine analytical applications. The ICP ion source has several unique advantages the samples are introduced at atmospheric pressure the degree of ionisation is relatively uniform for all elements and singly charged ions are the principal ion product. Theoretically, 54 elements can be ionised in an ICP with an efficiency of 90 % or more. Even some elements that do not show ionic emission lines should be ionised with reasonable efficiency (namely, As, 52 % and P, 33%) [381]. This is one of the advantages of ICP-MS over ICP-AES. Other features of ICP-MS that make it more attractive than ICP-AES are much lower detection limits ability to provide isotopic ratio information and to offer isotope dilution capabilities for quantitative analysis and clean and simple spectra. The... 

Isotope dilution (ID) is a technique for the quantitative determination of element concentrations in a sample, on the basis of isotope ratios [382]. An important prerequisite for isotope dilution is the availability of two stable isotopes, although in some cases the use of long-lived radionuclides allows the application range to be further extended [420]. 

Macrocyclic Compounds in Analytical Chemistry. Edited by Yury A. Zolotov Surface-Launched Acoustic Wave Sensors Chemical Sensing and Thin-Film Characterization. By Michael Thompson and David Stone Modern Isotope Ratio Mass Spectrometry. Edited by T. J. Platzner High Performance Capillary Electrophoresis Theory, Techniques, and Applications. Edited by Morteza G. Khaledi... 

Evershed, R. P., Amot, K. I., Collister, J., Eglinton, G. and Charters, S. (1994) Application of isotope ratio monitoring gas chromatography mass spectrometry to the analysis of organic residues of archaeological origin. Analyst 119, 909 914. 

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