“…Procedures for the determination of trace amounts, which cannot be used within the framework of conventional spectrophotometry (for example, for the determination of metals inolved in aqua complexes), deserve attention. 29,43,77,86,87,353,357 Studies devoted to thermal lens techniques for the detection of individual rare-earth metals and their mixtures 30,31,62,70,80 are of most interest. In this case, virtually no additional sample preparation is required, because absorption bands of aqua complexes of rareearth metals are rather narrow, due to which they can be selectively determined in soils, 30 waters 80,81 and uranium fuel 70 at a level of y610 77 ± y610 76 mol ml 71 .…”