Copper natural abundance ratios

Figure 4.2 shows the SIMS spectrum of a promoted iron-antimony oxide catalyst used in selective oxidation reactions. Note the simultaneous occurrence of single ions (Si+, Fe+, Cu+, etc.) and molecular ions (SiO+, SiOH+, FeO+, SbO+, SbOSi+). Also clearly visible are the isotope patterns of copper (two isotopes at 63 and 65 amu), molybdenum (seven isotopes between 92 and 100 amu), and antimony (121 and 123 amu). Isotopic ratios play an important role in the identification of peaks, because all peak intensities must agree with natural abundances. Figure 4.2 also illustrates the differences in SIMS yields of the different elements although iron and antimony are present in comparable quantities in the catalyst, the iron intensity in the spectrum is about 25 times as high as that of antimony ... 

Germanium minerals are extremely rare but the element is widely distribnted in trace amounts. Its abundance ratio is about 7 x 10 % and it is mainly associated with copper, zinc, lead, selenium, arsenic, silver, iron, and so on. There are twenty-one isotopes Ge, Ge, Ge, Ge, Ge are naturally occurring. Germaiuum is common in organisms, but it is not an indispensable trace element. In humans, it is nontoxic, but when it reaches 1000 ppm in animal s food, the growth of animals wifi be inhibited and 50% of them will die. 

Thermal ionization has been used to determine isotopic abundance of virtually all the elements We have recently extnded our own capability in this direction by adapting the silica gel/phosphoric acid filament coating technique (5) to our system Five 1 of a fine silica gel suspension is placed on a filament Five l of the analyte ion solution is coated, dried then coated with 2 pi of a 0 7N phosphoric acid solution and heated until dry again The analysis is performed in a similar manner as before, except that the signal is more transient and somewhat less intense than the calcium analysis With this approach, however, we have made natural abundance isotope ratio measurements on zinc, copper, and magnesium Table II shows our measurements compared to the accepted values, shown in parenthesis, for these elements The isotope used as reference... 

The reproducibility of mass spectra was checked also with the help of a standard Cu wire, determining the characteristic isotopic ratio of copper Cu63/Cu65. The laser produced totally consecutive 165 shots and the isotope ratio was calculated for every shot by the areas under the mass peaks. The average value of the so calculated isotope ratios was estimated to be 2.24 6%, which fully corresponds to the natural abundance distribution of 2.24. Similar measurements with the same instrument with a standard reference material (SRM 610) of NBS showed an averaged value of 2.24 1% from 50 consecutive laser shots. It is obvious that the differences in the two measurements are a function of different homogeneity of the targets. 

The principle of EDMS is surprisingly simple. A sample with known isotopic composition but unknown element content is mixed with an accurately known amount of spike. This spike contains the analyte element in a non-natural isotopic composition the ideal is to use a spike that has an enrichment of the rarest natural isotope. After complete mixing of the sample and spike the so-called isotope diluted sample (blend) has a new isotope ratio, which lies between the isotope ratio of the sample and the isotope ratio of the spike. This is demonstrated in Figure 4.8 for the example of copper. The sample shows the natural isotopic composition of copper, which is 69.17% of Cu and 30.83% of Cu. The spike is enriched in Cu (91.90%) the abundance of Cu is 8.10%. After complete mixing, the isotope diluted sample (hlend) shows a new isotope ratio Cu/ Cu, which directly reflects the analyte concentration in the sample. 

---