Lead isotope analysis advantages

Lead isotopic analysis (J, 2, 3, 4, 5) is a relatively new member of this expanding group of complementary methods. Like the others, it has its own peculiarities, advantages, and disadvantages which have been described. Lead isotope studies help to identify possible geographical origins of the ores from which ancient leads were smelted. Even where specific mines cannot be identified, the objects can still be classified as to which could or could not have had a common origin. The method requires only small sample sizes, and the results are independent of the histories of the objects studied. 

Despite the advantages that curse tablets offer for such an analysis, there are a few problems that must be considered when analyzing these artifacts. First, only a very small portion of the curse tablet can be sampled and then used for analysis (7). Typical samples collected were only a few grams from the edge of the tablet. This limits the ability to ensure the tablets are homogenous. Furthermore, the samples were usually badly corroded (7). While this should not have an affect on the lead isotope values, it could change other trace element abundances. 

The above discussion exemplifies how a study of the different Mbssbauer parameters and their temperature dependences can give detailed information about the location of a non-Mossbauer isotope, lead, in its surrounding structure. It should perhaps for comparison be mentioned that the conventional technique of structure analysis, X-ray diffraction, did not enable the above information to be obtained, again showing the advantage of Mossbauer spectroscopy in the study of catalyst systems, which often may show X-ray amorphous features. 

In Chapter 8 a leading expert in the detection of adulteration of oils and fats, Rossell, explains the economic advantages which tempt unscrupulous dealers to add cheap oils to high-value oils such as olive oil. He then describes a technique which he and his coworkers at Bristol have pioneered where stable carbon isotope ratio (SCIR) measurement has simplified the task of detecting adulteration. He compares sterol and fatty acid methyl ester analysis with SCIR and shows how clearly the latter detects maize oil. 

The advantages of lead concentration and isotopic composition measurements by TIMS have established an important niche for this technique in research. This has occurred in spite of the relatively high costs of the instrumentation and supplies, expertise required for analyses and equipment maintenance, and the time required for TIMS measurements (see discussions in the isotope dilution and the isotopic composition measurement sections following). Coincidentally, measurements by TIMS have benefited from recent advances that have substantially lowered the costs of the instrumentation, dramatically simplified the analyses, and greatly accelerated the rate of analysis (e.g., the development of multicollector instruments and multisample turrets). 

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