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. Bien que, ces dernieres annees, la sensibilite et la precision des techniques analytiques modernes se soient continuellement ameliorees, les specifications analytiques traditionnelles concernant la tallies des particules des echantillons sont restees a 74 μm (-200 mesh). Pour cette raison, la contribution de I'erreur due a I'inhomogeneite des portions test de I'echantillon est devenue de plus en plus importante dans I'erreur analytique globale. En consequence, pour reduire cette erreur totale, le premier effort doit porter sur I'amelioration de I'homogeneite des echantillons en reduisant la faille des particules. Dans ce but, nous avons teste une methode de preparation de materiaux de reference ultra-fins. Six sediments marins MSAn et MSCS- 1 a 5 ont ete prepares en utilisant la technique de broyage ultra-fin (jet mill) et la repartition en taille des particules de ces echantillons a ete verifiee par granulometrie - laser. La taille moyenne des particules de ces echantillons etait de 4–5 μm et celle des particules les plus grosses ne depassait pas 30 μm. MSAn sera utilise pour le prochain test de competence GeoPT et les echantillons MSCS- 1 a 5 seront prepares pour devenir des materiaux de reference. Tous les laboratoires geochimiques sont invites a participer a ce programme de recherche de cooperation, L'utilisation d'echantillons ultra fins (< 30 μm) aura une influence significative dans les developpements futurs des techniques geoanalytiques car elle devrait permettre de reduire la taille des aliquotes d'analyse et le developpement de nouveaux systemes geoanalytiques.