Isotopes elements with single

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... 

Figures 5.19b and 5.19c represent the mass spectra of compounds with single chlorine and bromine atoms, respectively. Roughly, in the case of chlorine the ratio of intensities of A and A + 2 peaks is 3 to 1, and in case of bromine, 1 to 1. One should take into account that the presence of several atoms of A + 2 elements in the molecule results in the appearance of intense peaks M + 4, M + 6, etc., that is, the presence of two or more atoms of A + 2 elements in an ion again gives a unique ratio of isotopic peaks in the...

The number of stable isotopes for the naturally occurring elements tends to increase with increasing atomic number, to a maximum of 10 for Sn (Fig. 1). Elements with low atomic numbers tend to have the lowest number of stable isotopes, limiting the possible ways in which isotopic compositions can be reported. Both H and C have only two stable isotopes (Fig. 1), and therefore isotopic compositions are reported using one ratio, D/H and C/ C, respectively. Single ratios can only be used for B and N, and data are reported as "B/ B and W N, respectively. Of the non-traditional stable isotope systems discussed in this volume, only three have just two stable isotopes (Li, Cl, and Cu Fig. 1). 

Mass spectrometric measurements are based on measuring ion currents of separated ion beams of isotopes. With knowledge of the isotopic composition of the elements investigated (see Table of Isotopic Abundances in Appendix I5), a simple identification of chemical elements using singly... 

Of all the different mass spectrometric techniques for isotope analysis (such as ICP-MS, LA-ICP-MS, TIMS, GDMS, AMS, SIMS, RIMS and isotope ratio mass spectrometry of gases), the greatest proportion of pubhshed papers today concern ICP-MS with single and multiple ion collection.19 Due to its benefits, ICP-MS has now become a widely accepted method for isotope analysis and allows isotope ratios to be measured in a short time with good accuracy and precision.9,19,75 78 As discussed above, as a powerful and universal tool, ICP-MS has opened up new applications for isotope ratio measurements of elements with a high first ionization potential, which are difficult to analyze with TIMS (such as Mo, Hf, Fe). Of all the heavy metals studied, uranium was favoured by ICP-MS and LA-ICP-MS. 

The detection of individual species is possible with certain methods. One can, with radioactive isotopes, measure a single atom. This, however, does not imply that methods using radioisotopes are better than those using stable isotopes. This paradox is explained by considering that in order to measure a radioactive atom, it is necessary that it decomposes during the time of the measurement. Thus if a radio-element has a long lifetime, the chance of observing this decomposition will be small. 

The response of an atom to the strength of the external magnetic field is different for different elements, and for different isotopes of the same element. The resonance frequencies of most nuclei are sufficiently different that an NMR experiment is sensitive only to a particular isotope of a single element. The frequency for H is 200 MHz at 4.7 T, but that of l3C is 50.4 MHz. Thus, when recording the NMR spectrum of an organic compound, we see signals only for H or 13C, but not both H and l3C NMR spectra are recorded in separate experiments with different instrument settings. 

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]. 

In order to demonstrate the analytical capabilities of LI-MS, the results it provided for glass samples were compared with those obtained using other multi-element and microanalytical techniques to determine 30 trace elements [195]. This comparison revealed the number of elements that can be determined by LI-MS to be similar to that of other multi-element techniques such as instrumental neutron activation analysis (INAA) or LA-ICP-MS. However, INAA was unable to determine some geochemically interesting trace elements such as Nb and Y, and LA-ICP-MS analyses were occasionally disturbed by the formation of argon clusters. In contrast to LA-ICP-MS, LI-MS can also measure single-isotope elements such as Nb, Y, Pr and Ho also, it requires no wet chemistry. 

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