Trace elements profiling

Figure 9.8 Trace element profile along a single hair using LA-ICP-MS. The horizontal axis refers to the tracking time of the laser along the hair, which equates to distance, (a) shows lead along individual hairs from different depositional environments A is a modern sample, B is an experimentally buried modern sample, C is from a surface-exposed (8 months) forensic case, and D is an archaeological sample (died 1867). (b) shows arsenic from three of these same samples. There is clearly postdepositional uptake of both elements in the archaeological samples, and in these particular examples little evidence of lateral variation.

Trace element profile along a single hair using LA-ICP-MS 211... 

In the other limiting case of D/ > D, the trace element profile approaches uniform concentration because the trace element diffuses much more rapidly than the equilibrium-determining component. 

Elements are incorporated into teeth from the diet or by inhalation. The figure shows trace element profiles measured by laser ablation—plasma ionization-mass spectrometry of the dentine of teeth from a modem person and one who lived in Scandinavia about a.d. 1800. The contrast is striking. The old tooth contains significant amounts of tin and bismuth, which are nearly absent in the modern tooth. The old tooth contains more lead and antimony than the modem tooth. Tin and lead are constituents of pewter, which was used for cooking vessels and utensils. Bismuth and antimony also might come from pewter. 

Trace element profile of a tooth from a modem man and from a person who lived in Scandinavia 200 years ago. /From a. cox. 

The trace element profile of teeth at the opening of this chapter was obtained by inductively coupled plasma-mass spectrometry. Figure 21-28 shows an example in which coffee beans were extracted with trace-metal-grade nitric acid and the aqueous extract was analyzed by inductively coupled plasma—mass spectrometry. Coffee brewed from either bean contains —15 ngPb/mL. However, the Cuban beans also contain Hg at a concentration similar to that of Pb. 

Therefore, when using the trace element profile of a food to assign its geographical origin, one also has to consider what other factors (apart from the underlying geology) may have influenced the profile. 

However, it is not just the presence or absence of an element that is useful (as most elements will be present at some concentration), but it is the relative variation in the trace element profile that is the parameter that provides the major discriminatory power. McHard et al. [16] were possibly some of the first researchers to apply a normalization procedure to multielement data in order to maximize the differences between two sets of samples. Their approach, which is now accepted as being a standard tool for use in chemometric investigations, was to identify an element whose concentration was constant, irrespective of the geographical origin of the samples, and then to normalize all other elemental data against it. In McHard s study on fruit juice, they used Zn. The authors of this chapter used Ca in an egg authenticity study, where eggshells were used as the sample matrix (unpublished data) and Mg was used in a study of Welsh onions [14]. 

Since the early days of ICP, there have been many investigations, showing the usefulness of trace element profiling. However, in recent times, the use of mass... 

Therefore in the concluding section, a brief overview is given of studies where light isotopic ratios and/or heavy isotopic ratios and/or trace element profiling have been combined in order to optimize the technologies available for investigating the geographical provenance of foods. 

So far, in this chapter, individual techniques have been taken into account that have been used in the elucidation of the geographical origin of foods. It has been seen how trace element profiling and heavy isotope ratio measurements reflect the underlying geohydrological environment on which the food was produced. However, it has been shown how quite a wide range of chemical and biological... 

Brewer P. G., Spenser D. W., and Robertson D. E. (1972) Trace element profiles from the GEOSECS II test station in the Sargasso Sea. Earth Planet. Sci. Lett. 16, 111-116. 

Luminescence banding Color (gray scale) banding Trace element profiles... 

Given that flowstone and stalagmites may provide relatively continuously time lines that can be accurately calibrated by U/Th dating, it is possible to extract paleoclimatic signals beyond the bulk deposition of the calcite itself. This has been accomplished by tracking various isotope and trace element profiles. Samples can be drilled at sufficiently close intervals along a sawed slab of stalagmite or flowstone to provide profiles with a time resolution of a few tens to a few hundred years. 

Efforts have been made over the past several years to identify airborne metals with specific emission sources by the use of enrichment factors, and by comparing the trace element profile of airborne particles with characteristic components in particulate matter from various sources. Measurements of particle size and the application of sophisticated statistical techniques should increase the accuracy of these "fingerprinting approaches. 

Shacklette HT, Eedman JA and Haems TF (1978) Trace elements in plant foodstuffs. In Oehme FW, ed. Toxicity of Heavy Metals in the Environment Part 1, pp. 25-68. Marcel Dekker, New York. Steinnes E (1997) Trace element profiles in ombrog-enous peat cores from Norway evidence of long-range atmospheric transport. Water Air Soil Pollut 100 405-413. 

PIXE, being an ion-beam based trace-element technique, is capable of analyzing at a lateral resolution of micrometres (Malmqvist, 1986). This has been used, for example, in a study of mercury migration in teeth with amalgam fillings (Lindh and Tveit, 1980). In a more recent investigation, trace element profiles in human blood cells were determined by microPIXE (Johansson and Lindh, 1987). 

Some specific problems undertaken include location of heavy metals in soil specimens due to application of sewage sludge, trace element profiling in electrical insulators, analysis of air particulate collected at urban locations, multilayer thin film analysis of solar cells. 

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