Investigations into the Preparation of Ultra-Fine Particle Size Geochemical Reference Materials

Although over recent years, sensitivity and precision of modern analytical techniques have continuously improved, traditional analytical specification for the particle size of samples has remained at 74 μm (-200 mesh). For this reason, the uncertainty caused by inhomogeneity in test portions of the sample itself has become a more and more significant contribution to the total analytical uncertainty. Therefore, to reduce this total uncertainty, the first step is to improve the homogeneity by reducing the particle size of a sample. For this purpose, we have investigated a method for the preparation of ultra-fine reference materials. Using the modern ultra-fine crushing technique (jet mill), six marine sediment samples MSAn and MSCS-1 to 5 were prepared and the particle distributions of these samples were measured using a laser particle-analyser. The average particle size of these samples was 4–5 (im and the largest particle size was less than 30 (im. MSAn will be used as the sample for a future GeoPT(tm) proficiency testing round and MSCS-1 to 5 will be prepared as reference materials. All geochemical laboratories are welcome to participate in this co-operative research programme. The processing and use of ultra-fine samples (< 30 μm) will have a significant influence on the future development of geoanalytical techniques as a consequence of the potential reduction in the mass of test portion and the development of new geoanalytical systems.