CHEMICAL SPECIATION OF NICKEL IN AIRBORNE DUSTS - ANALYTICAL METHOD AND RESULTS OF AN INTERLABORATORY TEST PROGRAM

Analytical knowledge, qualitative and quantitative, of the various nickel species present in the airborne dusts of nickel-producing and nickel-using workplaces is required for the assessment of nickel-related health hazards. A wet-chemical procedure is described which apportions the airborne nickel species into four categories: water soluble, "sulfidic", metallic, and "oxidic". The sample is leached in a sequence with ammonium citrate, hydrogen peroxide-ammonium citrate, and bromine-methanol, each of which selectively dissolves a number of related nickel species. Each leach solution and the insoluble residue from the third leach are then analyzed for nickel. The underlying chemistry of each leaching step is discussed, and its selectivity and completeness is evaluated. Since real workplace samples usually contain a limited number of species which are linked to the feeds and processes used and the final products, this 4-fold categorization is generally adequate to speciate the sample. The suitability of various filter materials for sampling airborne dusts for the purpose of speciation is examined. Problems caused by natural alkalinity of glass fiber filters are discussed. The results of an international interlaboratory test program of this nickel speciation method are reported.