The mentioned elements are known to occur in the environment in different oxydation states with different biological activities. Speciation of the oxydation state by selective enrichment can lead to relevant information for the toxicologist. A sample treatment procedure is described that --allows to discriminate between the oxidation states of the mentioned elements --converts the elements to the optimum oxydation state for enrichment from the sample --brings the elements in an ideal form for their determination by x-ray fluorescence analysis using coprecipitation with the dibenzyl-ammoniumsalt of dibenzyldithiocarbamic acid. An outline of the method, instrumentation used and applications to organic, biological and environmental samples is given.