HEAVY ELEMENT DETERMINATIOiV IN HEALTH-RELATED ORGANIC MATRIX MATERIALS BY TOTAL REFLECTION X-RAY FLUORESCENCE

Recent developments in TXRF techniques make the method appropriate for simple, accurate and precise analysis of heavy elements in organic materials in health-related and pollution problems. Special advantages are derived by the use of monochromatized beams of Xrays: i) The reduction in the spectrum background allows direct irradiation of organic matter specimens. Hence human tissue and body fluids are prepared by simple procedures involving dilution, homogenization and standard addition avoiding the need for specimen digestion. This results in faster, cheaper methods that decrease sample contamination problems. ii) The presence of a large Compton scattered signal in the spectrum and its use as an internal standard reference allows further simplification by avoiding the need to add an element as internal standard in test specimens. Quantification methods rely on determination of spectrometer sensitivity relative to the Compton peak. Required use of standard reference materials or matrix matching for this purpose may be substituted by a semiempirical reference model or by the use of a standardized specimen made from the unknown by spiking with elements absent in the matrix. Applications include trace element determination in amniotic fluid in fetus malformation studies, analysis of brain specimens and cerebrospinal fluid in central nervous system disorders, the influence of trace elements in cataract genesis and blood, body fluids and tissue drug-level monitoring. Accuracy, precision and detection limits attained in the analysis of platinum in minute amounts of serum and urine from oncological pediatric patients undergoing chemotherapy with Ptcontaining drugs shows TXRF to be the most appropriate technique for routine monitoring of platinum blood levels in cancer patients. INTRODUCTION The importance of heavy elements in human health studies is well established.1,2 Normal healthy organism contains a number of essential heavy elements, which play an important role in the human physiology. Monitoring of body fluids for disease diagnosis or assaying for the presence or absence of toxic elements is part of the modern arsenal of the physician. The introduction in the human body of foreign heavy elements for diagnosis or therapeutic reasons has become common practice. However, all invasive procedures, which involve the introduction in the body of heavy elements either as contrast media, as essential constituents of radiopharmaceutical compounds or as integral parts of drugs must consider the risk-benefit balance of their use. The development of simple accurate and precise procedures of heavy element monitoring is important to reduce the risk and to maximize the benefits. A number of modern analytical techniques are appropriate for trace element analysis of the human body3. Techniques such as Graphite Furnace Electrothermal Atomization Atomic Absorption Spectroscopy (GF-ETA&U), Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), Neutron Activation Analysis (NAA) and Total Reflection X Ray Fluorescence (TXRF) are appropriate for determination of metals at very low concentration levels. Organic samples of human origin have been analyzed previously by TXRF using various sample preparation techniques: by sample chemical digestion4, by cold plasma ashing’ and by Copyright(c)JCPDS-International Centre for Diffraction Data 2000,Advances in X-ray Analysis,Vol.43 570