ELEMENTAL ANALYSIS OF ENVIRONMENTAL-SAMPLES BY TOTAL-REFLECTION X-RAY-FLUORESCENCE - A REVIEW

A review of total reflection x-ray fluorescence (TXRF) as an effective excitation mode for energy-dispersive x-ray spectral analysis is pres ented. The instrumental conditions of excitation under grazing inciden ce (psi < 0.1 degrees) are emphasized and the analytical features of p owerful detection and simple and reliable quantification are character ized. The applicability of TXRF to environmental analyses is illustrat ed by some typical examples. The analysis of pure water samples leads to detection limits at the ppt (ng/l) level. A special matrix separati on is only needed for river, sea and waste waters. The analysis of air dust is directly possible with a sampling volume of 1 m(3) and a samp ling time of 1 h. Organ tissue can be analysed down to the lower ppm r ange after freeze-cutting of mu m thick sections. Plant material has t o be pulverized and digested prior to analysis, e.g. with nitric acid. In combination with a chromatographic separation, speciation is made possible for small 0.5 ml fractions, e.g. for vegetable foodstuffs. Fo r all these applications a multi-element determination can be carried out, for about 20-25 elements simultaneously. Simple and reliable quan tification is effected by internal standardization. The reliability of the method has been proved by intercomparison tests. Second-generatio n instruments that are compact and user-friendly are now commercially available.