A selective determination of elemental selenium(Se(0))was developed and was applied to a soil extract to clarify whether Se(0)is one of the soluble forms of soil selenium or not. (1)After transformation of Se(0)contained in a soil extract, into selenocyanate ion(SeCN^-)by reaction with cyanide ion, the SeCN^- was extracted in the form of ion-pair with zinc 1, 10-phenanthroline cation chelate into nitrobenzene-chloroform(1:1)mixture solvent. Then, the SeCN^- in the solvent was back-extracted into an aqueous solution of NaOH. Thus, SeCN^- ion separated from coexisting components contained in a soil extract was determined as selenium derived from Se(0). (2)By this method, Se(0)more than 1-2 μg kg^<-1> extracted from soil was selectively determined and Se(0)formed in the extract by reduction of Se(IV)with ascorbic acid as a reducing agent was completely recovered. No remarkable interferences caused from thiocyanate ion(SCN^-)which has similar chemical properties to SeCN^- were found. (3)The method proposed was applied to the water extract of air-dried and incubated soils. The amount of Se(0)found in the extracts was less than 1-2 μg kg^<-1>. The result indicated that Se(0)was not the dominant form of soluble selenium in soil. (4)The simultaneous determination of SeCN^- and SCN^- was also performed by use of highperformance liquid chromatography. The two ions were separated by reverse-phase ion-pair chromatography and were electrochemically determined with high sensitivity by measuring the oxidation current of the ions on a glassy carbon electrode applied at +1.0V(vs. Ag/AgCl).
