Vol.9 No.2 2016

Research paper : Development and utilization of geochemical reference materials (T. OKAI)−64−Synthesiology - English edition Vol.9 No.2 (2016) The most notable characteristic of these two samples is that contamination was strictly prevented. Geochemical reference materials are fundamentally prepared by grinding massive rocks into powders; therefore, a certain amount of contamination from the crusher cannot be avoided. The details are discussed in Chapter 4. The mixing in of iron, etc., from the steel crushers that were generally used in the 1960s was tolerated, and for those who were actually conducting chemical analyses, as long as the mixing was uniform and did not impact the decomposition of samples, it did not interfere with the utilization of the reference materials. However, from the perspective of elucidating the chemical composition of rocks that represent Japan, contamination needed to be minimized as much as possible; thus, sample rocks were crushed with mortar and pestle made of the same rock (“tomozuri” method). This process took a large amount of time and effort, but because of sufficient care, Japan attained the utmost trust in its reference materials from international organizations as the following comment shows: “The reference materials of Japan are prepared with extreme care and reflect the composition of original rocks directly.” As a result, in addition to normal chemical analysis values, isotopic ratios and ages of rocks were reported, and physical constants such as elastic wave velocity and breaking strength[7] were reported from rock fragments. At the time, there was no other example of reporting on the physical constant of the reference materials for chemical analysis, and these results were highly appraised globally. By virtue of being globally utilized as such, the stock of both samples was exhausted and distribution was discontinued in the early 1980s. Therefore, in 1984, as re-prepared samples of JG-1 and JB-1, JG-1a and JB-1a were newly prepared by using the same source rock. It is impossible to make reference materials of identical elemental contents even when the same source rocks are used. Therefore, newer batches of reference materials were given subscripts, a, b, c, etc., to differentiate them.3.2.2 High evaluation leads to project statusThe success of the first two types of reference materials led to a significant change in the atmosphere of geochemical reference material development. The research effort for initial development in 1964 was part of basic research and its budget was limited. However, because of the high praise the work received, it became a project—special research “study of rock reference material preparation” of the Geological Survey—in 1981. After it became a special project, the rate of preparation increased, and in 1982, the third reference material, JA-1 (andesite, Mount Hakone), was prepared. Since then, two to three types of new reference materials have been prepared each year, and around 1990, 17 types of the first volcanic rock series (two of these are the re-prepared types mentioned above) were prepared, and these were followed by nine types of the sedimentary rock series. Thus, the goal of “rocks that represent Japan” was mostly completed. This achievement was highly praised as seen in the following comment: “GSJ’s reference materials represent the most representative rocks of Japan, and their compositions are the same as the chemical compositions of the Japanese Islands.” Appended figures and tables in the “New Cyclopedia of Earth Sciences,” published in October 1996, presented the recommended values (standard values) of the main components of the 15 types of the volcanic rock series (excluding two types that were discontinued) and the nine types of the sedimentary rock series as the “major chemical composition of rock reference samples of the geological survey.”[8] In this manner, the significance of reference material preparation at GSJ was acknowledged widely. In addition, the advanced analytical technology at GSJ contributed greatly to its success. At the time, reference materials were distributed with initial analytical values analyzed by GSJ that was the issuing organization. Subsequently, analytical data were collected to determine the standard values. With this method, it took some time for the standard values to be decided. As the reliability of the initial analytical values analyzed by GSJ was high, these initial values were used as standard values in many general analytical labs.By 1990, the geochemical reference materials were distributed widely, and these materials were used regularly not only by initial research organizations but also by general analytical labs. Additionally, reference materials had been issued for many types of rocks. The list of geological reference materials summarized by Abbey in 1977[9] included 75 types issued by 16 organizations. In the list summarized by Potts in 1992,[10] the number of types had increased to 493 by 35 organizations, and new development for the project was being contemplated by GSJ.3.3 Changes in distribution of reference materials and instrumental analysis3.3.1 Changes in needsIn the early stage of reference material development, users were mostly universities and research organizations, which not only used reference materials but also participated in the decision on the values of reference materials. To present more accurate and precise standard values, they joined forces with the development organizations to prepare reference materials. However, as the development of reference materials became widespread and utilization by general analytical labs and researchers with less expertise in chemical analysis increased, most users simply used the pre-valued samples as reference materials rather than participating in value determination. The goal of developing analytical methods for research purposes did not change, but the original use of reference materials for accuracy management of analyses and preparation of calibration curves, etc., became mainstream. This was a natural progression of reference material development as it moved away from its initial


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