DETERMINATION OF CHLORINE AND BROMINE IN ROCKS BY ALKALINE FUSION WITH ION CHROMATOGRAPHY DETECTION

This study describes the use of alkaline fusion by sodium peroxide to dissolve chlorine and bromine in rocks to produce a solution which, wi th appropriate pre-treatment, is suitable for analysis by ion chromato graphy. Results are given for a selection of sedimentary and igneous r ocks. The accuracy of the fusion method is evaluated by analysis of Ge ological Survey of Japan reference materials. Additionally, a spike re covery rest is performed to show that the fusion process is quantitati ve for chlorine and bromine. The results for chlorine are in the range 58-3860 mg kg(-1) and show good agreement both with results obtained by pyrohydrolysis with flow injection colorimetric detection and resul ts obtained by aqueous leaching of the samples with ion chromatography detection. Results for bromine are in the range <3-4.5 mg kg(-1). Bec ause of the relatively few data obtained in this study and the relativ e paucity of published data for reference materials, an assessment of the accuracy of the fusion method for bromine is more difficult. The l imits of detection for this method are 36 and 3 mg kg(-1) for chlorine and bromine, respectively.