A RAPID, LOW-BLANK TECHNIQUE FOR THE EXTRACTION OF OSMIUM FROM GEOLOGICAL SAMPLES

Abstract

A new, rapid, low-blank method for extraction of osmium from geological materials is described. As with existing techniques, this new Os accumulation procedure relies upon the oxidation of Os in the sample solution to OsO4 and utilises the volatile nature of this oxide. In contrast to previous distillation methods, however, osmium oxide is caught in a cold trap, coated on its inner surface with sulfuric acid instead of bubbling an Os oxide bearing carrier gas through chilled HCl or HBr. Once the distillation is complete, the trapped Os is extracted into 500 μl of HBr concentration and undergoes a final cleaning step which can be accomplished by employing conventional micro-distillation techniques. The entire extraction procedure from the sample solution takes approximately 90 min and requires only 2 μl of H2SO4 to trap the osmium, which is achieved with great efficiency. Thus, apart from the digestion medium, the extraction and recovery of Os in this technique employs a total of only ~502 μl of reagents instead of approximately 5-10 ml in conventional procedures that 'see' the Os. As demonstrated here, the efficient extraction of Os and low reagent volumes required mean that it is possible to achieve yields of 80% and total procedural blanks of 100 fg routinely.