The certified values and uncertainties are expressed as mass fraction.

The referece values are expressed as mass fraction.

The property values of the material were determined statistically based on chemical analyses by 7 organizations (10 laboratories) using a wide range of methods. A property value satisfying the following conditions was accepted as a certified value: 1) the relative standard deviation associated with the mean of the laboratory means was 10 % or less; 2) the number of laboratories contributing to the mean of the laboratory means was at least eight; 3) the number of analytical methods contributing to the mean of the laboratory means was at least three. The uncertainty attached to the certified values is the expanded uncertainty using a coverage factor k=2, corresponding to the half-width of a confidence interval of approximately 95 %. A property value failing to satisfy one or two of the NIES criteria for certification but supplying valuable additional information about the material is given as a reference value. All certified and reference values were determined on an “as received” basis, that is, the values were determined without drying the material.

The CRM is supplied as fine powder in an amber glass bottle. The powder is beige in color.

The CRM was prepared from natural soil. The soil was collected at a landfill site in Japan and air-dried in the sun in 1998. Thereafter this material was sieved (106 µm), homogenized by a rotary blender, bottled (30 g each, 404 bottles) in amber glass bottles and finally sterilized by gamma radiation (21 kGy). All procedures complied with ISO Guide 34.

A stratified random sampling plan was devised to test for homogeneity across the lot of bottles and the homogeneity assessment was made based on analyses of the 1 mol/L hydrochloric acid extracts, in accordance with “The method of compliance test of the Ministry of Environment Japan, Notification 19 (March, 2003)”. The between-bottle variation evaluated by a one-way analysis of variance (ANOVA) showed the relative standard deviations between bottles for the analytes to be less than 1 %. The material, therefore, was judged to be sufficiently homogeneous for its intended use as a reference material.

1. Care should be taken to avoid contamination when opening the bottles. It is desirable to use up the contents as quickly as possible after opening.
2. This CRM should be kept tightly closed in its original bottle and stored in a desiccator at room temperature (≤ 30 ºC).
3. Prior to weighing portions for analysis, the contents of the bottle should be shaken gently.
4. It is recommended that a sample mass of 6 g is the minimum to be used for analysis, in accordance with “The method of compliance test of the Ministry of Environment Japan, Notification 19 (March, 2003)”.
5. Precautions should be taken to avoid inhalation of the material.
6. This CRM should not be used for purposes other than research. When disposing of the material, local laws concerning processing and disposal of waste materials should be strictly adhered to.
7. The mass fractions of elements in this CRM are reported on an “as received” basis without drying. This CRM, as received, has an average moisture content of approximately 1 % as measured in NIES by drying separate sub-samples for 4 h at 105 ºC.
8. In the case of measurement of As by ICP-MS, the possibility of spectral interference by Nd and Sm should be checked.

The expiry date for the certified values of this CRM is January 2029 assuming that the recommended storage conditions are adhered to. NIES will notify via its website if any changes in the contents are recognized within the term of validity.

The certified and reference values for this CRM were based on analytical values from the following seven participating organizations: 
National Institute for Environmental Studies; Environmental Control Center Co., Ltd.; IDEA Consultants, Inc.; MURATA Keisokuki Service Co., Ltd.; NIPPON STEEL & SUMIKIN TECHNOLOGY Co., Ltd; Research Institute of Environment, Agriculture and Fisheries, Osaka Prefecture; Tokyo University of Science

Information values may be useful for handling this material, though the values are not certified. These values are for “total element content” and not for acid-extractable content. 
Appendix Table Information values for total elemental content
The information values are expressed as mass fraction.