| Popis: |
One of the characteristic phenomena in the chemical sciences of the second half of the twentieth and the beginning of twenty-first century was rapid development in the analytical chemistry of traces. New purity standards for materials emerged at the beginning of the atomic era. Uranium used as a fuel in nuclear reactors and other materials useed in nuclear technology had to be as fully free as possible of certain elements (e.g., Dy, Gd) that have a high cross-section for the absorption of thermal neutrons. The requirement that the concentration of these and other elements (e.g., in nuclear-grade uranium) should not exceed a few milligrams per kilogram caused fast progress in such techniques as emission spectrography, spectrophotometry, and neutron activation analysis (NAA), as well as in separation and preconcentration methods for elements. Progress in electronics and the advent of semiconductor technology increased purity requirements in the materials sciences. At the same time, progress in the biomedical sciences drew attention to the role of trace elements essential for life (Co, Cu, Fe, I, Mn, Mo, Ni, Se, Sn) or that are toxic (As, Cd, Hg, Pb). The determination of these elements in tissues, body fluids, and so on is often the basis for medical diagnosis and therapy. On the other hand, ecological movements have focused on global environmental pollution. As a result, monitoring of several chemical compounds and trace elements in water, air, soil, and food has become the daily work of several laboratories. In our times, more and more frequently it seems that determination of the total concentration of a given element in the investigated object is not sufficient. The determination of various physical and chemical forms of an element (i.e., speciation analysis) is often required. In this period of globalization, rapid growth of international trade, and introduction of international standards, many important decisions (administrative, medical, commercial, technological, and those concerning environment protection) depend on the results of chemical analyses. |
