Elemental Analysis Catches Elephant Poachers

Similarly, because the ratios of 15N/14N and 87Sr/86Sr in elephant tusks also vary depending on the region of Africa the elephant inhabited, they can be used to trace the elephant s origin. In fact, using these techniques, scientists have reported 

There is now international concern about the dwindling elephant populations in Africa—their numbers have decreased by 40% over the past decade. This concern has led to bans on the export of ivory from many countries in Africa. However, a few nations still allow ivory to be exported. Thus, to enforce the trade restrictions, the origin of a given piece of ivory must be established. It is hoped that the isotope signature of the ivory can be used for this purpose.  

Most elements occur in nature as mixtures of isotopes thus atomic masses are usually average values. 

The mass for each element is given in the table inside the front cover of this book. This value, even though it is actually a mass, is sometimes called (for historical reasons) the atomic weight for each element. 

Look at the value of the atomic mass of carbon given in this table. You might expect to see 12 since we said the system of atomic masses is based on 12C. However, the number given for carbon is 12.01, because the carbon found on earth (natural carbon) is a mixture of the isotopes 12C, 13C, and 14C. All three isotopes have six protons, but they have six, seven, and eight neutrons, respectively. Because natural carbon is a mixture of isotopes, the atomic mass we use for carbon is an average value based on its isotopic composition. 

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Chemical Insights Elemental Analysis Catches Elephant Poachers 54... 

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